REESEH.LIBRARY     - 


UNIVERSITY  OF  CALIFORNIA. 


tAcc&sion  No. 


92331 


.    Class  No. 


J 


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V:..        I 


WORKS  OF 
AUSTIN  T.  BYRNE,  C.  E., 

PUBLISHED   BY 

JOHN  WILEY  &  SONS. 


Inspection   of   the    Materials    and    Workmanship 
Employed  in  Construction. 

A  reference  book  for  the  use  of  inspectors,  super- 
intendents, and  others  engaged  in  the  construction 
of  public  and  private  works.  12010,  cloth,  555  pp., 
$3.00. 

A  Treatise  on  Highway  Construction. 

Designed  as  a  text-book  and  work  of  reference 
for  all  who  may  be  engaged  in  the  location, 
construction,  or  maintenance  of  roads,  streets, 
and  pavements.  8vo,  cloth,  800  pp.,  %.oo. 


A  TREATISE 


HIGHWAY  CONSTRUCTION. 


DESIGNED  AS 

A  TEXT-BOOK  AND  WORK  OF  REFERENCE 

FOR  ALL  WHO  MAY  BE  ENGAGED  IN  THE 

LOCATION,  CONSTRUCTION,  OE    MAINTENANCE 

OF 

EOADS,  STEEETS,  AND  PAVEMENTS. 


BY 

AUSTIN  T.  BYENE,  C.E. 


FOURTH  REVISED  AND  ENLARGED  EDITION. 
FIRST   THOUSAND. 


NEW  YORK : 

JOHN    WILEY    &    SONS. 

LONDON:  CHAPMAN  &  HALL,  LIMITED. 

1900. 


COPYRIGHT,  1892,  1900, 

ay 
AUSTIN  T.   BYRNE. 


ROBERT  DRUMMOND,    PRINTER,   NEW  YORK. 


PKEFACE  TO  THE  FOURTH  EDITION. 


PURSUANT  to  the  purpose  of  the  author  and  the  publishers  to 
keep  this  work  abreast  of  the  times,  a  thorough  revision  of  the 
Third  Edition  has  been  made, — minor  errors  being  corrected, 
obsolete  matter  expunged,  and  considerable  new  matter  (some 
one  hundred  and  twenty-five  pages)  added.  Among  the  chapters 
expanded  are  those  on  Stone  Pavements,  Brick  Pavements, 
Broken-stone  Pavements,  and  Asphaltum  and  Coal-tar  Pavements. 
Included  in  the  new  matter  will  be  found  some  important  tables 
on  asphalt  production  and  manufacture,  the  comparative  cost  of 
laying  and  maintenance  of  pavements  in  various  cities  of  this 
country  and  Europe,  with  other  valuable  data,  and  a  number  of 
specification  forms. 

NEW  YORK,  November,  1900. 

iii 


92331 


PREFACE  TO  THE  THIRD  EDITION. 


THE  favorable  reception  of  the  previous  editions  and  the  advance 
made  in  every  branch  of  highway  construction  and  maintenance 
have  induced  the  author  to  revise  and  enlarge  the  work,  and  thus 
keep  up  witli  the  progressive  spirit  of  the  age  and  render  it  more 
worthy  of  approbation. 

A  large  amount  of  new  matter  has  been  added  and  many  im- 
portant alterations  have  been  made.  Defective  illustrations  have 
been  replaced  with  new  and  better  ones. 

Among  the  principal  additions  to  the  subject  matter  in  this 
edition  may  be  mentioned  the  articles  on  bitumen,  asphaltum,  and 
asphalt,  the  varieties  and  nomenclature  of  asphalt,  fluxes  for 
asphaltum,  causes  of  failure  of  asphalt  pavements,  tests  of  paving- 
brick,  blast-furnace  slag,  chert,  Florida  clay,  artificial  stone,  sta- 
tistics of  roads  in  the  United  States,  etc. 

The  selection  of  tools,  machinery,  and  other  articles  of  manu- 
facture for  reference  and  illustration  has  been  guided  solely  by 
their  merits  and  fitness  for  the  intended  purpose. 

The  writer  takes  this  opportunity  to  gratefully  acknowledge  the 
kindness  of  those  who  have  assisted  in  furnishing  data,  etc. 

A.  T.  B. 
NEW  YORK,  February,  1896. 

iv 


PEEFACE. 


ALTHOUGH  volumes  have  been  written  on  the  subject  of  high= 
way  construction,  still  the  matter  is  widely  scattered  through  the 
pages  of  the  standard  works  on  engineering,  technical  journals 
and  periodicals,  in  pamphlets  and  reports  of  city  engineers,  and  is 
therefore  not  always  easily  accessible  when  wanted. 

The  author,  having  found  the  need  of  a  comprehensive  and 
practical  work  of  reference  upon  the  many  subjects  connected  with 
highways,  has  in  the  following  pages  endeavored  to  collate  the 
Varied  mass  of  information.  In  doing  so  he  has  derived  valuable 
assistance  from  the  works  of  the  authors  mentioned  below  (which 
works  may  be  profitably  studied  by  those  desiring  further  infor- 
mation upon  the  subjects  treated  of),  and  takes  this  method  of 
acknowledging  his  indebtedness  and  thanks,  instead  of  inclosing 
every  extract  in  quotation-marks. 

AUTHORS  AND   PUBLICATIONS  REFERRED  TO. 

Allnutt.—Wood  Pavements;  Prize  Essays  on  Road-inaking  and  Main- 
tenance. 

A  Move  for  Better  Roads. 

Baker.—  Masonry  Construction;  Cost  of  Bad  Roads,  in  Report  of  the 
Illinois  Society  of  Engineers  and  Surveyors. 

Baumeister. — The  Cleaning  and  Sewerage  of  Cities. 

Boulnois.— Dirty  Dust-bins  and  Sloppy  Streets;  The  Municipal  and 
Sanitary  Engineer's  Handbook. 

£urgoyne.—On  Rolling  New-made  Roads. 

Burnett. — Selection,  Inspection,  and  Use  of  Cement  and  Mortar  (a 
paper  read  before  the  Engineers1  Club  of  St.  Louis). 

Brande. — Encyclopedia  of  Science,  Literature,  and  Art. 


VI  PREFACE. 


Callanan. — Roads  and  Road-making. 

Clark. — Recent  Practice  in  the  Construction  of  Roads  and  Streets 
(London). 

Cluss. — Mortars  and  Concretes  of  Antiquity  and  Modern  Times  (a 
paper  read  before  the  American  Institute  of  Architects). 

Codrington—  Maintenance  of  Macadamized  Roads. 

Dobson. — Pioneer  Engineering. 

Encyclopaedia  Britannica. 

Engineering  and  Building  Record. 

Engineering  Magazine. 

Engineering  News  and  American  Railway  Journal. 

Gillespie. — The  Principles  and  Practice  of  Road-making. 

OKllmore. — Roads,  Streets,  and  Pavements;  Limes,  Hydraulic  Cements, 
and  Mortars;  Strength  of  the  Building  Stones  in  the  United  States. 

Good  Roads. 

Greene. — The  Construction  and  Care  of  Streets  (a  paper  read  before 
the  Commonwealth  Club  of  New  York) ;  Asphalt  and  its  Uses  (a  paper 
read  before  the  American  Institute  of  Mining  Engineers);  Roads  and 
Road-making  (in  Harper's  Weekly). 

Harper's  Weekly. 

Haupt. — Common  Roads,  in  Reports  of  the  Pennsylvania  Board  of 
Agriculture;  The  Best  Arrangement  of  City  Streets,  in  Franklin  Institute 
Journal;  Importance  of  Good  Wagon-roads,  in  Engineering  Magazine; 
Engineering;  Specifications  and  Contracts. 

Hay  wood.— Reports  Addressed  to  the  Commissioners  of  Sewers  of  the 
City  of  London. 

Henck. — Field-book  for  Railroad  Engineers. 

Herschel. — The  Science  of  Road-making. 

Hughes.— The  Roads  and  Walks  of  Central  Park,  New  York. 

Hurst. — Architectural  Surveyor's  Handbook. 

Jeriks. — Road  Legislation  for  the  American  State. 

Journal  of  the  Association  of  Engineering  Societies. 

Journal  of  the  Franklin  Institute. 

Journal  of  the  Society  of  Arts. 

Knight. — American  Mechanical  Dictionary. 

Kuichliny.— Cement  Mortars  for  Use  in  Public  Works  (Report  to  the 
Executive  Board  of  the  City  of  Rochester,  New  York). 

Law. — The  Art  of  Constructing  Common  Roads. 

Lippincott's  Magazine. 

Love. — Pavements  and  Roads. 

McClanahan.—  Roads  and  Road -drainage,  in  Report  of  the  Illinois  So- 
ciety of  Engineers  and  Surveyors. 

Mahan—  Civil  Engineering. 


PREFACE. 


Manuel  de  I'lnggnieur  des  Fonts  et  Chauss6es. 

Mathewson. — City  Streets:  How  to  Build  them  and  Why  (a  paper  read 
before  the  Ohio  Society  of  Surveyors  and  Civil  Engineers). 

Molesworth. — Pocketbook  of  Formulae  and  Memorandum. 

Morin. — Aide  Memoir;  Experience  sur  le  Tirage  des  Voitures. 

Moseley. — Mechanics  of  Engineering. 

Nelson. — Making  and  Mending  of  Country  Roads,  in  Harper's  Weekly. 

Newberry—  The  Street  Pavements  of  New  York,  in  School  of  Mines 
Quarterly. 

North. — Construction  and  Maintenance  of  Roads;  Highways  and  Na- 
tional Prosperity,  in  Engineering  Magazine. 

Ny strom. — Pocketbook  of  Mechanics. 

Paget. — Report  on  the  Economy  of  Road  Maintenance  and  Horse-draft 
through  Steam  Road-rolling. 

Parnell. — Treatise  on  Roads. 

Paving  and  Municipal  Engineering. 

Pennell. — What  I  Know  about  European  Roads,  in  Harper's  Weekly. 

Pope. — Improvement  of  City  Streets. 

Potter. — The  Common  Roads  of  Europe  and  America,  in  the  Engineer- 
ing Magazine;  Our  Common  Roads,  in  the  Century  Magazine;  The  Gospel 
of  Good  Roads. 

Proceedings  of  the  Association  of  Municipal  and  Sanitary  Engineers 
and  Surveyors. 

Proceedings  of  the  Institution  of  Civil  Engineers. 

Rarikine. — Civil  Engineering. 

Reports  of  the  Engineer  Department  of  the  District  of  Columbia. 

Reports  of  the  Pennsylvania  Board  of  Agriculture. 

Reports  of  the  Tenth  and  Eleventh  United  States  Census. 

Reports  of  the  United  States  Geological  Survey. 

Reports  of  Various  City  Civil  Engineers. 

Rhatvn.—A  Plea  for  Better  Roads. 

Ripley.— Improved  Roads  (an  address  before  the  New  Jersey  State 
Board  of  Agriculture). 

School  of  Mines  Quarterly. 

Scribner's  Magazine. 

JSearles. — Field  Engineering. 

Shaler. — The  Common  Roads,  in  Scribner's  Magazine. 

Shurik.— Treatise  on  Railway  Construction  and  Location  for  Young 
Engineers. 

Smith.— Parks  and  Pleasure  Grounds. 

Speed.— The  Common  Roads  of  Europe,  in  Lippincott's  Magazine. 

Spon. — Dictionary  of  Engineering. 

Stone. 


Vlii  PREFACE. 


The  Century  Magazine. 

The  Clay  Worker. 

The  Manufacturer. 

The  Sanitarian. 

The  Technologist. 

The  Transit. 

Torrey. — Pavement  Construction  and  Economies  (an  address  at  the 
Street-paving  Exposition,  Indianapolis). 

Transactions  of  the  American  Society  of  Civil  Engineers. 

Transactions  of  the  Canadian  Society  of  Civil  Engineers. 

Trautwine. — Engineer's  Pocketbook. 

United  States  Consular  Reports  on  the  Streets  and  Highways  of  For- 
eign Countries. 

Vose. — Manual  for  Railroad  Engineers. 

WaddelL—  General  Specifications  for  Highway  Bridges. 

Wellington.—  The  Economic  Theory  of  Railway  Location. 

Wheeler.—  Repair  and  Maintenance  of  Roads. 

Wilkins. — Mountain  Roads,  etc. 

Wright. — Mechanical  Dictionary. 

Whipple. — Microscopy  of  Drinking-water. 

Wilkins. — Mountain  Roads,  etc. 

Wright.—  Mechanical  Dictionary. 


TABLE  OF  CONTENTS. 


CHAPTER  I. 
PAVEMENTS. 

PAGE 

Object  of  pavements — The  qualities  essential  to  a  good  pavement — The 
interests  affected  in  the  selection  of  pavements— Selection  of  suitable 
pavements — Cost  of  wagon  transportation — Cost  of  railroad  transpor- 
tation— Effect  of  reducing  the  cost  of  wagon  transportation— Problem 
involved  in  the  selection  of  the  most  suitable  pavement— Adaptability 
— Desirability — Economic  desirability  of  pavements — Tractive  force 
required  on  different  pavements — Number  of  horses  required  to  move 
a  given  load  on  different  pavements — Economy  of  smoothness — Ser- 
viceability—Comparative safety— Observations  of  Capt.  Greene — Ob- 
servations of  Col.  Hay  wood — Deductions  from  the  observations — Con- 
dition of  the  weather  and  slipperiness — Cause  of  the  difference  in  the 
observations  of  Capt.  Greene  and  Col.  Hay  wood — Slipperiness,  cure 
for — Durability — Causes  affecting  durability— Durability  of  different 
pavements — Cost  of  pavements — Cheapest  pavement — What  a  good 
pavement  should  cost — Economy  and  public  bodies — First  cost- 
Relative  economies  —  Maintenance  —  Prevailing  opinion  regarding 
pavements — Cleansing — Comparison  of  pavements  with  regard  to 
facility  for  cleaning — Annual  cost  for  service — Consequential  damages 
— Disadvantages  of  dirty  and  noisy  pavements — Gross  cost — Traffic 
census — Traffic  census  in  the  United  States — Weights  of  vehicles — 
Form  of  traffic  census — Tonnage— Guaranteeing  pavements— Deferred 
payments — Justification  of  contracts  for  maintenance — Destruction  of 
pavements — Amount  of  money  wasted  in  continually  opening  streets 
— European  methods •• .  •  1 

CHAPTER   IT. 
MATERIALS  EMPLOYED  IN  THE  CONSTRUCTION  OF  PAVEMENTS. 

Materials  employed  for  paving— Physical  and  chemical  qualities— Breaking 
and  crushing  tests— Methods  of  testing  durability— Method  of  testing 

ir 


TABLE   OF   CONTENTS. 


PAGE 

the  comparative  value  of  paving-stones— Absorptive  power—  Descrip- 
tion of  materials— Granite— Syenite— Amount  and   value  of  granite 
used  for  street  purposes  in  the  United  States— Price  of  paving-blocks 
—Various  uses  of  granite  —  Specific  gravity,  weight,  and  resistance 
to  crushing  of  various  granites— Manufacture  of  granite  blocks — Sand- 
stone— "  Bluestone  "—Commercial  names  of  sandstone— Analyses  of 
sandstone— Specific   gravity,    weight,   and    resistance  to  crushing — 
Amount  and  value  of  sandstone  used  for  street  purposes  in  the  United 
States — Amount  and  value  of  bluestone  used  in  1889— Limestone— Uses 
of  limestone — Experience  with  limestone — Specific  gravity,  weight,  and 
resistance  to  crushing — Amount  and  value  of  limestone  used  in  1880 — 
Trap-rock — Specific   gravity,    weight,    and   resistance   to   crushing — 
Bitumen — Asphaltum — Asphalt— Origin— Occurrence — Distribution — 
Nomenclature — Composition — Refined  asphaltum — Refining  asphaltum 
— Asphaltic  cement— Flux  for  asphaltum— Liquid  asphalt— Petroleum 
residuum  —  Examination   of — Specifications  for  —  Asphaltic  paving 
materials — Bituminous  limestone — Manner  of  using  bituminous  lime- 
stone— Analysis  of  European  bituminous  rocks — Bituminous  sandstones 
— Manner  of  using  the  sandstone — Trinidad  Asphaltum — Character- 
istics of  crude  Trinidad— Composition  of  Trinidad  asphaltum — Refined 
Trinidad  asphaltum — Refining  Trinidad    asphaltum— Characteristics 
of  refined  Trinidad  asphaltum — Bermudez  asphalt — California  asphal- 
tum— Buena  Vista  asphalt — Asphalt  mastic — analysis  and  tests  of  as- 
phaltum— Penetration  tests — Analysis  of  California  asphaltum — Prices 
of  asphaltum  in   1897-98 — Production  and  varieties  of,  in  the  United 
States — Imports  of,  to  the  United  States — Percentage  of  the  uses  of 
asphaltum  —  Paving-pitch  —  Gas-tar — Brick  —  Clay — Composition   of 
clay — Quality   of    clay   required    for    paving-brick — Manufacture    of 
paving-brick — Repressed  brick — Analyses  of  clay— Characteristics  of 
good  paving-brick — Tests  of  paving-brick — Standard  tests  adopted  by 
the  National   Brick   Manufacturers'   Association  —  Specific    gravity, 
weight,  and  resistance  to  crushing— Absorptive  power  of  brick— Tests 
of  Ohio  paving-brick — Wood — Quality  of  wood — Creosoting — Specific 
gravity,   weight,  and  resistance   to  crushing— Absorptive   power  of 
wood— Sand— Use,  price,  and   weight  of — Gravel — Shingle— Chert — 
Specific  gravity,  weight,  and  resistance  to  crushing  of  various  sub- 
stances .        .        .        .        .        .  ,.     .        .        .       ..        •        .        .    24 

CHAPTER  III. 
STONE  PAVEMENTS. 

Early  stone  pavements— Cobblestone  pavement — Specifications  for— Bel- 
gian-block pavement— Specifications  for— Granite-block  pavement- 
Advantages  and  defects  of  granite-block  pavements— Quality  of  stone 
for  pavements — Size  and  shape  of  the  blocks— Dressing  the  blocks — 


TABLE   OF   CONTENTS. 


PAGE 

Manner  of  laying  the  blocks — Gauging  the  size  of  the  blocks — Founda- 
tion for  the  blocks — Cushion-coat — Joint-filling — Bituminous  cement — 
Sandstone-block  pavements — Limestone-block  pavements — Pavements 
on  steep  grades — Durability  of  granite  blocks — Wear  of  granite  block 
— Cost  of  maintaining  granite-block  pavements — Method  of  paying  for 
granite-block  pavements — Number  of  blocks  to  the  square  yard — Cost 
of  construction  of  granite- block  pavements — Cost  of  Belgian-block 
pavements — Cost  of  sandstone-block  pavements — Cost  of  cobblestone 
pavements — Heads  of  specifications  for  granite-block  pavements.  .  99 


CHAPTER   IV. 
WOOD   PAVEMENTS. 

Success  of.  in  Europe — Failure  of,  in  America — Advantages  of — Objections 
to — Wood  pavements  and  death-rate — Systems  of  wood  pavements — 
Size  and  form  of  the  blocks — Number  of  blocks  per  square  yard — Es 
sentials  necessary  to  successful  construction — Foundation  for  wood 
pavements — Chief  causes  of  failure — Quality  of  the  wood — Chemical 
treatment  of  the  wood — Dimensions  of  the  blocks — Expansion  of 
wood  blocks — Width  of  joints— Filling  for  joints — Durability  of 
wood  pavements — Duration  and  life  of  wood  pavements  in  European 
and  American  cities — Wear  of  wood  pavements — Cost  of  wood  pave- 
ments— Cost  of  maintaining  wood  pavements — Description  of  various 
systems  of  wood  paving — Heads  of  specifications  for  wood-block  pav- 
ing—Maintenance of  wood  pavements  by  contract— Specifications  for 
cedar-block  pavements — Microbes  in  wood  pavements — Cedar-block 
pavements — Karri  (Australian)  block  pavement — Creosoted  pine  blocks 
— Cottonvvood  and  gurn  blocks— Redwood  block  pavement — Jetley's 
patent  ....  >  .  *,  *  .-  .  .  .  .124 


CHAPTEK   V. 
ASPHALTUM  AND  COAL-TAR  PAVEMENTS. 

Introduction  of  asphalt— Difference  between  European  and  American 
asphalt — Advantages  of  asphalt — Defects  of  asphalt — Asphalt  pave- 
ment injured  by  illuminating-gas— Durability  of  asphalt— Wear- 
Cost  of  construction— Extent  of  asphalt  pavements  in  1897-99— Cost 
of  maintenance — Foundation— Asphalt  cement  pavements— Composi- 
tion of — Failure  of — Trinidad-asphalt  pavements — Composition  of, 
preparation  of— Memoranda— Extracts  from  reports  of  city  civil  en- 
gineers—Experiments with  asphalt  pavements  in  various  cities- 
Heads  of  specifications  for  standard  Trinidad-asphaltum  pavement- 
Specification  for  asphaltum  pavements  on  bituminous  base— On  Ly- 


TABLE   OF   CONTENTS. 


PAGE 

draulic  base — On  surface  of  old  pavements — Specifications  for  asphalt 
pavement,  Washington,  D.  C.,  1899 — Maintenance  of  asphalt  pave- 
ments under  contract — Berinudez  asphalt — European  asphalt  pave- 
ments— Bituminous-limestone  pavements  in  America — Coal-tar  pave- 
ments— Coal-tar  and  asphaltuin — Vulcanite  pavement — Advantages 
and  defects  of  coal-tar  or  distillate  pavements— Specifications  for  coal- 
tar  distillate  pavements — Asphalt-block  pavements— Advantages  and 
defects— Cost  of  asphalt-block  pavements — American  bituminous-rock 
pavements — Specifications  for— Expansion  of  asphalt— Repairs  to 
asphalt  pavements — Specifications  for  the  repairs  of  asphalt  pave- 
ments— For  the  condition  of  asphalt  pavements  at  end  of  guarantee 
period  .  .  .  ,  '.....  .  .  .  .  .  ,:'^  ":  .157 


CHAPTER  VI. 

BRICK  PAVEMENTS. 

Advantages  and  defects  of  brick  pavements— Durability  of — Size  and 
shape  of  the  bricks—Quality  of  the  bricks— Foundation  for— Sand 
cushion — Manner  of  laying— Joint-filling— Cost  of  brick  pavements- 
Variety  of  systems — Heads  of  specifications  for  brick  pavement — Ex- 
tract from  paving-brick  specifications — Rumbling  in  brick  pavements 
— Number  of  brick  and  block  required  per  square  yard — Brick  paving 
for  country  roads—Average  price  of  paving-brick  per  thousand  in  1898  219 

CHAPTER  VII. 
BROKEN-STONE  PAVEMENTS. 

Introduction  of  broken- stone  pavements— Methods  of  Tresaguet,  Tel  ford, 
and  Macadam — Modern  Tel  ford  and  Macadam  pavements — Defects  of 
Telford  system — Defects  of  Macadam  system— Advantages  of  broken- 
stone  pavements — Defects  common  to  all  broken-stone  pavements 

Essentials  requisite  to  successful  construction— Erroneous  methods  of 
construction — Quality  of  the  stone — Abrasion  and  cementation  tests  of 
stone— Size  of  the  stones— Shape  of  the  stones — Breaking  of  the  stone 
—Hand-breaking— Cost  of  breaking  by  hand— Amount  broken  by  hand 
— Stone-crushers— Cost  of  operating  crushers — Amount  of  stone  broken 
by  crushers— Dimensions,  capacity,  etc.,  of  stone-crushers— Cost  of 
quarrying  and  crushing  stone— Voids  in  broken  stone— Weight  of 
broken  stone — Area  covered  by  a  cubic  yard  of  broken  stone Thick- 
ness of  the  broken  stone— The  New  Jersey  and  Bridgeport  roads- 
Number  of  cubic  yards  of  broken  stone  required  per  mile— Spreading 
the  stone — Thickness  of  the  layers — Binding,  necessity  of,  qualities  of 
—Injurious  effects  of  large  amounts— Practice  of  the  French  engin- 
eers—Watering— Compacting  the  broken  stone,  by  traffic,  by  horse- 


TABLE    OF    CONTENTS.  xiil 


PAGE. 

rollers,  by  steam-rollers — Defects  of  traffic  consolidation — Advantages 
of  rolling — Defects  of  horse-rollers — Introduction  of  steam-rollers — 
Advantages  of  steam-rolling — Pressure  exerted  by  rollers  and  by 
loaded  vehicles— Defects  of  wide  rollers — Objections  to  picks  on 
steam-rollers — Steepest  grade  on  which  a  steam-roller  can  be  operated 
— Cost  of  maintaining  steam-rollers — Amount  of  rolling — Manner  of 
applying  the  roller — Cost  of  rolling — Cost  of  broken-stone  pavements 
— Cost  of  broken- stone  roads  in  Massachusetts — Difference  in  cost  of 
broken-stone  pavements  in  Europe  and  America — Wear  of  broken- 
stone  pavements — Effect  of  climate  on  broken-stone  roads — Cost  of 
maintaining  broken-stone  pavements  —  Specifications  of  modern 
broken-stone  roads  in  England — Methods  of  construction  adopted  iu 
Chicago,  in  Bridgeport,  in  St.  Louis — Heads  of  specifications  for 
broken-stone  pavements  .  .  .  .  .  .  »  ... .'  .  .  .  24& 


CHAPTER   VIII. 

MISCELLANEOUS  PAVEMENTS. 

Gravel,  quality  of— Preparing  and  laying  the  gravel— Repairing  gravel 
roads— Cost  of  construction— Weight  of  gravel— Bituminous  macadam 
— Preparing  and  laying — Concrete  macadam — Stone  trackways,  ad- 
vantages of — Trackways  in  Italy— Cost  of  stone  trackways— Jasperite 

A»tificial-granite   blocks — Plank  roads — Method  of  construction — 

Life  and  cost  of  plank  roads— Log  roads— Charcoal— Iron— Blast- 
furnace slag — Chert— Florida  clay — Tar-macadam— Artificial  stone — 
Hydraulic  cement— Clinkers— Glass— Novaculite— Destructor  concrete 
—  Cork  — Copper  slag— Steel  trackways  —  India  rubber  —  Artificial 
paving-stones— Asphaltina— Asphalt-granite  pavement  .  .  . 

CHAPTER  IX. 

FOUNDATIONS. 

Necessity  of  foundations -Essentials  necessary  to  the  forming  of  stable 
foundations-Influence  of  the  character  of  the  soil-Defects  of  sand 
and  plank  foundations-Blast-furnace  slag  as  a  foundation-mater.al- 
Concrete,  advantages  of-Thickness  of  the  concrete-Quality  o 
concrete-Strength   of  the  concrete-Specific  gravity  of  concrete- 
Proportions-Determination  of  voids  in  the  broken  stone-Voids  in 
sand-Quantity  of  water,  some  of  the  usual  proportions-Mixing,  la 
ing   and  ramming  the  concrete-Transverse  strength   of  . 
Compressive  strength  of  concrete-Cost  of  concrete-Proportions  for 
Portland-cement  concrete-Limes,  characteristics  of-Cements,  nat, 
ral    and    artificial-Tests    of    cement-Characteristics    of    Portland 
cement-Testing  cement-Composition  of  mortar-Quality  and  quan- 


TABLE    OF   CONTENTS. 


PAGE 

tity  of  sand— Quantity  of  water— Strength  of  mortar— Effect  of  frost 
on  mortar— Weight  of  cement— Specifications  for  concrete— Specifica- 
tions for  the  preparation  of  the  roadbed— Foundation  employed  in 
Liverpool 319 

CHAPTER  X. 
RESISTANCE  TO  TRACTION. 

Conditions  causing  resistance  to  traction— Want  of  uniformity  of  the 
surface— Resistance  of  penetration— Rolling  resistance  of  wheels- 
Experiments  of  M.  Dupuit— Friction — Resistance  to  traction  on  differ- 
ent road-surfaces— Experiments  of  MM.  Dupuit  and  Morin— Gravity- 
Tractive  power  of  horses  and  gradients— Work  done  by  a  horse— 
Loss  of  tractive  power  on  inclines — Effect  of  inclines  on  the  load  a 
horse  can  draw — Steep  grades  objectionable — Equivalent  length  of 
inclined  and  level  roads— Character  of  vehicles — Width  of  tires— Size 
of  wheels— Effect  of  wheels— Wheel  diameters  .  .  ...  366 

CHAPTER  XI. 
LOCATION  OF  COUNTRY  ROADS. 

Considerations  governing  location — Principles  governing  location — Econ- 
omy of  motive  power — Selection  of  best  route — Reconnoissance,  object 
of — Points  to  be  attended  to  in  making  reconnoissance  —Configuration 
of  the  country — Ridges  and  passes — Watercourses  and  valleys — 
Streams  give  the  direction  of  the  high  ground  —  Preliminary 
survey — Data  to  be  obtained  on  preliminary  surveys — Topography 
— Map — Memoir — Levels — Cross-levels — Profile — Bridge  sites — Prin- 
ciples to  be  observed  in  making  final  selection — Examples  of 
cases  to  be  treated — Intermediate  towns — Mountain  roads — Method 
of  surveying  mountain  roads — Loss  of  height — Water  on  mountain 
roads — Halting-places — Alignment — Curves,  kind  of — Reduction  of 
grade  on  curves — Increasing  wheelway  on  curves — Excessive  crook- 
edness to  be  avoided — Curving  roads,  advantages  of — Zigzags,  objec- 
tions to — Final  location — Construction  profile — Gradient,  definition 
of — Determination  of  gradients — Angle  of  .repose,  to  ascertain — Trac- 
tive power  required  in  descending  inclines— Men  and  animals  ascend- 
ing steep  slopes — Maximum  grade  and  traffic — Maximum  grade  to 
be  adopted — Maximum  suitable  for  various  pavements — Maximum 
adopted  by  Telford — Maximum  adopted  by  the  French  engineers — 
Smooth  and  rough  surfaced  inclines — Determination  of  maximum 
grade — To  determine  the  most  advantageous  grade — Cost  of  grades — 
Grade  of  mountain  roads — Minimum  grade — Minimum  grade  adopted 
by  the  French  engineers — Undulating  grades— Level  stretches,  objec- 
tions to— Vertical  curves,  application  of — Different  methods  of  desig- 
nating the  same  grades  ..........  389 


TABLE   OF   CONTENTS.  XV 


CHAPTER   XII. 

WIDTH  AND  TRANSVERSE  CONTOUR. 

PAOB 

Width  of  roadways— Minimum  width — Advantage  of  wide  roads — Width 
of  land  appropriated  for  road  purposes  in  various  localities — Width 
of  mountain  roads — Number  of  acres  required  per  mile  for  different 
widths — Transverse  contour,  object  of — Amount  of  rise  required  for 

different  pavements — Form  of  transverse  contour — Form  for  streets 

Form  for  country  roads— Excessive  rise,  evils  of— Straight  sides  ob- 
jectionable—Concave form  not  desirable — Contour  on  hillside  roads  .  416 

CHAPTER   XIII. 
EARTH-WORK. 

Earth-work,  definition  of — Equalizing  earth-work — Transverse  balancing 
— Borrow-pits — Spoil-banks — Staking  out  of  borrow-pits — Shrinkage 
of  earth — Increase  of  rock — Settlement  of  embankments — Failure  of 
earth- work — Stability  of  earth-work — Angle  of  repose  of  earths — 
Angle  of  slopes — Effect  of  moisture  on  earth — Angle  of  slopes  in  rock 
excavation — Form  of  side  slopes — Protection  of  side  slopes— Slips — 
Catch- water  ditches — Drainage  of  side  slopes — Embankments,  best 
materials  for — Manner  of  forming  embankments — Slopes  of  embank- 
ments— Drainage  of  embankments — Embankments  over  plains— Em- 
bankments across  marshes — Description  of  an  embankment  formed 
by  Mr.  G.  Waite,  C.E. — Embankments  across  bogs — Embankments 
on  hillsides — Roadways  on  rock-slopes — Rock  excavation — Blasting 
— Quantity  of  rock  loosened — Line  of  least  resistance — Quantity  of 
powder  required — Cost  of  excavating  rock — Haul — Cost  of  earth-work 
— Loosening  earth — Transport  of  earth — Limits  to  which  shovels, 
wheelbarrows,  carts,  scrapers,  and  dump- wagons  may  be  employed — 
Loosening  and  transporting  by  machinery — Calculating  amount  of 
earth-work — Calculation  of  half-widths  and  areas — Examples  of  cross- 
sections  of  earth- work— Calculation  of  sectional  areas— Formulae  for 
the  calculation  of  areas — Table  of  cubic  contents  ....  421 

CHAPTER   XIV. 
DRAINAGE   AND  CULVERTS. 

Drainage,  object  and  necessity  of — Methods  employed  for  securing  drain- 
age— Division  of  natural  soils — Mitre-drains — Tile-drains— Silt-basins 
— Protection  of  drain-outlets — Cost  of  drains — Fall  of  drains — Side 
ditches — Springs,  treatment  of— Drainage  of  the  surface— Protection 
of  gutters— Water-breaks  objectionable— Catch- water  ditches— Cul- 
verts— Area  of  water-way — Rainfall — Determination  of  area  of  water 
way — Catch-pools — Materials  for  culverts — Cement  and  earthenware 


TABLE    OF   CONTENTS. 


PAGE 

pipes,  dimensions  and  cost  of — Iron  pipe-culverts,  dimensions  and  cost 
of — Box-culverts — Arch-culverts — Thickness  of  arch — Thickness  of 
abutments — Dimensions  and  cost  of  drain-tile— Discharging  capacity 
of  circular  pipes 45£ 

CHAPTER  XV. 
BRIDGES,  RETAINING-WALLS,  PROTECTION  WORKS,  TUNNELS,  FENCING. 

Bridges,  importance  of — Care  in  their  construction — The  loads  for  which 
bridges  should  be  proportioned — Materials  for  bridges— Wood — Types 
of  timber  bridges — Diagrams  and  dimensions  of  timber  bridges — Sub- 
structure of  bridges — Retaining- walls — Proportions  of  retaining- walls 
— Form  of  retaining-walls — Dry-stone  retaining-walls— Foundation  of 
retaining-walls — How  retaining-walls  fail— Coping  for  retaining-walls 
— Weep-holes — Formulae  for  calculating  the  thickness  of  retaining- 
•walls — Surcharged  walls — Least  thickness  of  retaining-walls — Where 
retaining-walls  should  be  built  —  Protection  of  roads  —  Parapets, 
dimensions  of — Earth  mounds — Wooden  railings  afford  no  protection 
— Guard-stones — Roads  along  the  seashore,  margin  of  rivers  and 
lakes— Bulkheads  and  masonry  walls — Tunnels— Fences— Cost  of 
fencing  .  .  .  ....  .  .  .  .  .  .  480 

CHAPTER    XVI. 
CITY   STREETS. 

Laying  out  of  streets— Best  arrangement  of  streets — Width  of  streets — 
Street  grades — Grade  at  street-intersections — Accommodation  summits 
— Transverse  grade — Transverse  contour — Sub-foundation  drainage 
of  streets — Surface  drainage  of  streets — Gutters— Catch-basins— Street 
lines  and  monuments — Street  profiles — Increasing  the  width  of  the 
carriageway  at  street  corners  .  .  ;  •  •  •"•  .  .  500 

CHAPTER  XVII. 

FOOTPATHS,   CURBS,   GUTTERS. 

Footpaths,  definition  of — Qualities  required — Width — Cross-slope — Foun- 
dation— Surface  requirements— Materials  employed  for  footpaths- 
Stone,  manner  of  dressing — Specifications  for  flagstones— Wood — 
Asphalt — Proportions  and  materials  employed  in  Paris — Number  of 
square  yards  that  a  ton  of  prepared  asphalt  will  lay— Life  of  asphalt 
footways— Specifications  for  asphalt  footway  pavements — Brick — Spe- 
cifications for  brick  walls — Artificial  stone,  varieties  of — Formation  of 
artificial  stone— Wear  of  artificial  stone — Specifications  for  concrete 


TABLE   OF   CONTENTS. 


PAGE. 

footwalks — Specifications  for  artificial-stone  footwalks— Tar  concrete 
— Specifications  for  tar- concrete  footpaths— Gravel,  manner  of  con- 
structing— The  Central  Park  walks — Drainage  of  gravel  walks — 
General  directions  for  the  construction  of  gravel  walks — Curbstones — 
Setting  curb — Specifications  for  granite  curb — Specifications  for  blue- 
stone  curb— Specifications  for  setting  curb — Specifications  for  artificial- 
stone  curb  and  gutter — Specifications  for  dressing  old  curb — Specifica- 
tions for  resetting  curb — Hollow  curbs — Gutters — Specifications  for 
cobble  gutters — Specifications  for  brick  gutters — Specifications  for  gut- 
ter-stones—Crossing  or  bridge-stones — Specifications  for  bridge-stones 
— Specifications  for  relaying  bridge-stones— Prices  ....  52T 

CHAPTER  XVIII. 
RECONSTRUCTION  AND  IMPROVEMENT  OF  COUNTRY  ROADS. 

Rectification  of  alignment  and  grades — Drainage — Improvement  of  the  sur- 
face—Improving clay  roads — Improving  sand  roads — Scraping  or  road 
machines,  manner  of  using — Cost  of  constructing  earth  roads — Cost  of 
maintaining  earth  roads — Value  of  improvements,  how  to  ascertain — 
Data  required — Defects  of  existing  roads — Profit  of  eliminating  unnec- 
essary grades — Profit  of  eliminating  unnecessary  length — Profit  of  im- 
proving the  surface — Annual  loss  occasioned  by  bad  roads  .  .  .  577 

CHAPTER    XIX. 
MAINTENANCE.— REPAIRING  ;  CLEANSING  ;  AND  WATERING. 

Maintenance,  definition  of— Necessity  of — What  good  maintenance  com- 
prises— System  of  maintenance — Maintenance  of  country  roads — Direc- 
tions for  maintaining  macadamized  highways — Errors  commonly  com- 
mitted in  the  maintenance  of  broken-stone  roads — Amount  of  water 
required — Cost  of  maintenance— Repair— Organization  of  road  force — 
Instructions  to  roadmen — System  of  highway  maintenance  adopted  in 
France — Street  cleansing — Intervals  at  which  it  is  performed — Ob- 
jections to  dusty  streets — Dirt-producing  causes — Composition  of  street 
dust — Amount  of  refuse  collected  from  city  streets— Amount  of  dirt 
produced  by  different  pavements— Methods  employed  for  cleansing — 
Systems  of  executing  the  work— Cost  of  cleansing — Methods  of  cleans- 
ing employed  in  Berlin,  Paris,  London,  Baltimore,  Boston,  and  other 
American  cities — Street  orderly  system — Cost  of  street  sweeping — 
Amount  of  surface  swept  by  one  man — Amount  of  surface  swept  by  a 
machine  broom — Cost  of  operating  mechanical  sweepers — Brooms — 
Carts  and  wagons — Disposal  of  street  dirt — Removal  of  snow — Methods 
employed— System  adopted  in  Milan — Disposal  of  snow— Weight  of 
snow — Street  washing — Street  sprinkling — Systems  employed — Quan- 
tity of  water  required— Cost  of  sprinkling  —  Sea- water  for  street 
sprinkling— sanding  pavements  .  ......  ..  .  •  .  585 


TABLE    OF   CONTENTS. 


CHAPTER   XX. 

TREES. 

PAGE 

Opinions  regarding  the  planting  of  trees  on  roads  and  streets — Trees  on  the 
French  and  Belgian  roads — Financial  value  of  trees — Fruit-trees  in 
Saxony— Selection  of  trees — Qualities  necessary  to  good  road-trees — 
Distance  apart  to  plant  trees— Trees  at  street- intersections — Protection 
a  trees 647 

CHAPTER  XXI. 
STAKING  OUT  THE  WORK. 

Object  of — Distance  apart  of  stakes — Straight  lines  and  curves— Side 
slopes — Setting  out  culverts — Length  of  culverts — Setting  out  bridges 
— Drains,  setting  out — Setting  out  vertical  curves— Staking  out  trans- 
verse contour  of  street  pavements — Setting  stakes  for  curb — Setting 
stakes  for  any  structure — Fixing  lines  upon  water — Bench  marks  .  652 

CHAPTER  XXII. 
SPECIFICATIONS  AND  CONTRACTS. 

Specifications,  contents  of — Tests  of  materials — Contracts — General  speci- 
fications for  clearing  —  Close-cutting  —  Grubbing — Grading — Forma- 
tion of  embankments — Earth-work,  measurement  and  classification — 
Drains — Catch-water  ditches — Off-take  ditches — Rip-rap — Retaining, 
breast,  slope,  and  parapet  walls— Culverts— Masonry,  classification 
of — Arch-culvert  masonry— Centring — Laying  masonry  in  freezing 
weather — Pointing — Grouting — Brick  masonry — Dry  walls — Dry  box- 
culverts  —  Pipe  culverts  —  Cement  —  Cement  tests —  Sand — Mortar — 
Concrete — Foundation  excavation — Artificial  foundations — Timber  — 
Piles  —  Cofferdams  —  Wrought-iron  —  Cast  iron — General  stipulations 
applicable  to  all  contracts — Interpretation  of  specifications— Omissions 
in  specifications — Engineer  defined — Contractor  defined — Notice  to 
contractor,  how  served— Preservation  of  engineer's  marks  and  stakes 
— Dismissal  of  incompetent  persons — Spirituous  liquors — Quality  of 
mate/.als — Samples — Deviations  from  plans  and  specifications — Right 
reserved  to  alter  details — Inspectors — Defective  work — Measurement 
of  work — Excavation — Overhaul — Masonry — Timber — Piles — Culverts 
and  drain-pipe — Stone,  brick,  and  pole  drains— Concrete — Curbing — 
Gutters — Crossing  or  bridge-stones  —  Catch-basins  —  Bridges  —  Pave- 
ments— Partial  payments — Commencement  of  work — Time  of  comple- 
tion— Progress  of  work — Forfeiture  of  contract — Damages  for  non- 
completion — Evidence  of  payment  of  claims — Protection  of  persons 
and  property — Bond  for  faithful  performance  of  work — Power  to  sus- 
pend work — Loss  and  damage — Miscellaneous  work — Cleaning  up — 


TABLE    OF    CONTENTS. 


PAGH 

Personal  attention  of  contractor — Contract  not  to  be  assigned — Payment 
of  workmen — Prices — Payments,  when  made — Heads  of  specifications 
for  a  highway — Specifications  for  a  bulkhead— Heads  of  specifications 
for  grading,  macadamizing,  curbing,  and  flagging — Specifications  for 
the  supply  of  broken  stone — Indemnification  for  patent  claims — In- 
demnity bond — Right  to  construct  sewers — Old  materials,  disposal  of — 
Security  retained  for  repairs — Alteration  of  manhole  covers,  stopcock 
boxes,  etc. — Heads  of  specifications  for  repaying — Specifications  for 
street  cleansing — Instructions  to  bidders — Form  of  proposal — Form  of 
agreement — Form  of  bond — Specifications  for  team  labor — Specifica- 
tions for  sprinkling — Form  of  monthly  certificate — Affidavit  of  con- 
tractor— Certificate  of  final  acceptance  .  .  .  .  ...  .  659 

CHAPTER  XXIII. 
IMPLEMENTS  AND  PRICES. 

Description  and  prices — Tools  for  clearing—Tools  for  grading— Mechanical 
graders — Tools  for  draining — Tools  for  rock  excavation — Hand-drills 
— Steam-drills— Tools  for  macadamizing — Stone-crushers — Sprinkling- 
carts —  Horse  rollers  —  Steamrollers — Tools  employed  in  the  main- 
tenance of  macadam  roads — Tools  employed  for  block  pavements — 
Concrete-mixing  machines — Tools  employed  for  asphalt  pavements — 
Tools  used  for  cleansing  pavements — Mechanical  sweepers— Street 
patrol  hand-cart— Sprinkling-carts— Snow-shovels  and  ploughs— Tools 
employed  for  artificial  stone  pavements— Catch-basins— Sewer-inlets 
and  gutter-crossings—Street  name-plates— Direction  indicators— The 
viagraph  .  .  .  .  •  •  «  •  •  •  •  •  710 

CHAPTER  XXIV. 

MISCELLANEOUS  NOTES. 

Comparison  of  European  and  American  Methods  and  Prices— Statistics  of 
Roads  in  the  United  States— Average  Weight  of  Load  for  Horses- 
Average  Cost  of  Haulage  per  Ton  per  Mile— Average  Length  of  Haul 
from  Farms  to  Market— Average  Total  Cost  per  Ton  for  the  Whole 
Length  of  Haul— Pavements  and  Horseshoes— Annual  Cost  of  Struc- 
tures—Interest and  Sinking-fund  Tables— Sprinkling  Oil  on  Roads- 
Sinking  Funds— Annual  Cost  of  Pavements— Relative  Economy  of 
Materials  .  .  .  .-  '  /  '  •  •  •  •  •  •  •  •  793 

APPENDIX  I.— Naming  and  Numbering  Country  Roads  and  Houses  .  808 

APPENDIX  II.— Methods  of  Assessing  the  Cost  of  Street  Paving     .  .  818 

APPENDIX  III.— Ordinance  Regulating  the  Width  of  Wagon-tires  .  821 

APPENDIX  IV.— Cycle-paths    .         /.'.••        V  „     -   .     • .      /•  -8 

INDEX  *\      •  ''*.'  •        •  -     •        '        '        *        '  '  825 


LIST  OF  TABLES. 


NUMBER  PAGE 

1.  Cost  of  wagon  transportation  on  different  road-surfaces 3 

2.  Tractive  force  required  upon  level  roads  of  different  materials 6 

3.  Comparison  of  gross  cost  of  pavements 18 

4.  Comparative  rank  of  pavements 21 

5.  Absorptive  power  of  stone 27 

6.  Specific  gravity,  weight,  and  resistance  to  crushing  of  granites 29 

7.  Production  and  value  of  granite  in  the  United  States  in  1889  for  street 

uses 30 

8.  Analyses  of  sandstones 33 

9.  Specific  gravity,  weight,  and  resistance  to  crushing  of  sandstones  ....  34 

10.  Production  and  value  of  sandstone  in   the  United  States  in  1889  for 

street  uses 35 

11.  Production  and  value  of  bluestone  used  for  street  purposes  in  the 

United  States  in  1889 35 

12.  Specific  gravity,  weight,  and  resistance  to  crushing  of  limestones 37 

13.  Production    and  value  of  limestone  used  for  street   purposes   in  the 

United  States  in  1880 ...:..  37 

14.  Specific  gravity,  weight,  and  resistance  to  crushing  of  trap-rocks 38 

14«.  Composition  of  asphaltum 43 

15.  Analyses  of  European  bituminous  rocks 52 

16.  Composition  of  Trinidad  asphaltum 55 

17.  Prices  of  asphaltum  in  1897-98  74 

18.  Production  of  asphaltum  in  the  United  States 74 

18a.  Varieties  of  asphaltum,  etc.,  produced  in  the  United  States 75 

19.  Imports  of  asphaltum  in  1897-98 75 

20.  Analyses  of  clay 82 

21.  Tests  of  paving-brick 87 

21a.  Tests  of  Ohio  paving-brick 88-P.l 

22.  Specific  gravity,  weight,  and  resistance  to  crushing  of  wood- 92 

23.  Absorptive  power  of  wocd 93 

24.  Specific  gravity,  weight,  and  resistance  to  crushing  of  various  sub- 

stances    97 

25.  Wear  and  duration  of  granite  pavements  in  London 114 

xx 


LIST    OF   TABLES.  XXI 


NUMBER  PAGE 

26.  Number  of  granite  blocks  to  the  square  yard 117 

27.  Cost  of  granite-block  in  various  cities  in  the  United  States  in  1890 118 

28.  Extent  and  cost  of  Belgian-block  in  the  United  States  in  1890  ... 119 

29.  Extent  and  cost  of  sandstone-block  in  the  United  States  in  1890 119 

30.  Extent  of  cobblestone  pavement  in  the  United  States  in  1900 120 

31 .  Duration  and  cost  of  wood  pavements  in  London 136 

32.  Wear  of  wood  pavements 138 

33.  Extent  and  cost  of  wood  pavements  in  various  localities 139 

34.  First  cost  and  cost  of  maintaining  wood  pavements  in  London.  .*. 140 

35.  Extent  and  cost  of  asphalt  pavements  in  various  cities 169-172 

35#.  Cost  of  maintaining  asphalt  pavements 173 

36.  Cost  of  asphalt-block  pavements  in  various  cities 210 

37.  Cost  of  brick  pavements 228-230 

38.  Coefficients  of  quality  of  stones 260 

39.  Cost  of  quarrying  and  crushing  stone 268 

40.  Number  of  cubic  yards  of  broken  stone  required  per  mile  of  road 271 

41.  Cost  of  broken-stone  roads 281 

42.  Cost  of  broken- stone  pavements  in  various  cities 282 

43.  Cost  of  gravel  pavements 301 

44.  Amount  of  water  absorbed  by  Portland  cement 336 

45.  Adhesive  strength  of  mortars 345 

46.  Shearing  strength  of  mortars 346 

47.  Tensile  strength  of  mortars 347 

48.  Effect  of  size  of  grain  of  sand  on  tensile  strength  of  mortar 350 

49.  Character  of  sieves  for  sifting  sand 350 

50.  Resistance  to  traction  on  different  road-surfaces 372 

51.  Tractive  force  on  a  level 375 

52.  Resistance  of  gravity  on  different  grades 375 

53.  Tractive  power  of  horses  at  different  velocities 378 

54.  Duration  of  a  horse's  daily  labor  and  maximum  velocity  unloaded. . . .  378 

55.  Increase  in  tractive  power 378 

56.  Maximum  amount  of  labor  a  horse  is  capable  of  performing  at  differ- 

ent velocities 379 

57.  Gross  load  which  a  horse  can  draw  on  different  grades 380 

58.  Effect  of  grades  upon  the  loads  a  horse  can  draw  on  different  pave- 

ments  381 

59.  Force  required  to  draw  loaded  vehicles  on  inclines  and   equivalent 

level  roads v 383 

60.  Best  width  of  wheel-tires » •  •     •  384 

61 .  Coefficient  of  resistance  for  different  pavements • 408 

62.  Methods  of  designating  grades. •  •  •  414 

63.  Number  of  acres  required  per  mile  for  different  widths  of  roadways. ..  417 

64.  Amount  of  transverse  rise  for  different  pavements 418 

65.  Natural  slopes  of  earth 425 

66.  Lengths  and  angles  of  slopes 425 


LIST    OF   TABLES. 


NUMBER  PAGK 

67.  Amount  of  powder  required 442 

68.  Capacity  of  drill-holes 442 

69.  Coefficient  for  different  earth-slopes 451 

70.  Earth-work  table e 453 

71.  Cost  and  weight  of  vitrified  culvert-pipe 471 

72.  Cost  and  weight  of  Portland-cement  pipe 471 

73.  Dimensions,  weight,  and  prices  of  iron  pipe 472 

74.  Dimensions  of  box-culverts 474 

75.  Thickness  of  arches 476 

76.  Thickness  of  abutments 478 

77.  Dimensions,  weight,  and  prices  of  drain-tile 479 

78.  Discharging  capacity  of  circular  pipes 479 

79.  Span  and  dimensions  of  bridges 484 

80.  "       "  "          "        "      485 

81.  Coefficients  for  thickness  of  retaining- walls 492 

82.  Width,  maximum  grade,  and  average  width  of  sidewalks  in  several 

cities 508 

83.  Street  statistics  of  various  cities 526 

84.  Number  of  square  yards  that  one  ton  of  prepared  rock  asphalt  will 

lay 530 

85.  Composition  of  dirt  from  paved  streets 622 

86.  Amount  of  refuse  collected  from  city  streets 623 

87.  Average  cost  per  head  of  population  for  street  maintenance  in  various 

cities 627 

88.  Wages  in  European  countries 793 

89.  The  amount  of  one  dollar  at  compound  interest  for  a  term  of  years.  800-802 

90.  The  annual  sinking  fund  that  with  compound  interest  will  amount  to 

one  dollar  at  the  end  of  a  term  of  years 803-805 


LIST  OF  ILLUSTRATIONS. 


FIGURE  PAGE 

1.  Roman  pavements 100 

2.  Coblestone  pavements , 100 

3.  Belgium  block  pavement 100 

4.  Early  granite-block  pavements 100 

5-7.  Improved  granite-block  pavement 103 

la,  Ib.  Street-intersection  paved  with  granite  blocks 106,  107 

8.  Cobblestones  on  steep  grades 112 

9,  10.  Granite  block  on  steep  grades «, 112 

12.  Section  showing  joint-filling 128 

13.  Plan  of  street  paved  with  wood  blocks 128 

13a.  Pavement  of  round  blocks 129 

14.  15,  15a,  156.  Sections  of  asphalt  pavements 158,  Io9 

15c,  15tf.  Asphalt  with  brick  gutter 16«j 

16,  17.  Hale  brick  pavement 220 

18.  Section  of  brick  pavement  on  concrete 220 

19    Plan  showing  arrangement  at  junction 220 

19a.  Plan  of  brick  paving  at  street  intersections 224 

19&.  The  Hayden  paving-block 231 

19c.  Cross-section  macadam  road  with  brick  trackway 244 

19d.  Cross-section  brick  trackway  underdrained 244 

20.  Broken-stone  pavements  in  France  previous  to  1775 247 

21 .  Tresaguet's  system 247 

22.  Telford's  system 247 

23.  Macadam's  system 247 

24.  Shape  of  stone  for  broken-stone  pavements 265 

2o-28.  Type  sections  of  broken -stone  pavements /. . . .  296 

29-32.  Stone  trackways 304,  305 

32^.  Cross-section  of  steel  trackway 317 

33.  Form  of  briquette  for  testing  tensile  strength  of  cement 341 

34.  Clamps  for  holding  briquette 341 

35.  Cement-testing  machine 341 

36.  Diagram,  resolution  of  forces  in  overcoming  obstacles  on  roads 36<5 

xxiii 


LIST   OF   ILLUSTRATIONS. 


FIGURE  PAGE 

37-39.  Diagrams  illustrating  resistance  of  penetration 368,  369 

40.  Resolution  of  the  force  of  gravity  on  inclined  planes 376 

41.  Mechanical  advantage  of  wheels 387 

42.  Contour  map 393 

43.  Map  of  preliminary  surveys 394 

44.  Preliminary  profile 395 

45.  Diagram  road  between  two  distant  towns 399 

46.  Simple  curve 402 

47.  Compound  curve.. 402 

48.  Reverse  curve 402 

49.  Double  reverse  curve 402 

50.  Construction  profile 405 

51-53.  Application  of  vertical  curves 415 

54.  Transverse  contour  of  streets , 419 

55.  Transverse  contour  for  country  roads 419 

56.  Hillside  road  showing  stepping  of  slopes  and  retaining- walls 428 

57.  Formation  of  embankments  by  end  dumping 430 

58.  ."          "  "  "layers 431 

59.  Usual  method  of  forming  embankments 432 

60.  Embankments  over  plains 433 

61.  62.  Embankments  on  hillsides,  manner  of  stepping  the  slope 437 

63-65.  Embankments  of  rock-slopes 438,  439,  440 

66-68.  Formation  of  a  road  in  the  face  of  a  cliff 440 

69.  Profile  of  cut  and  fill  illustrating  calculation  of  overhaul 446 

70-76.  Examples  of  earthwork  cross-sections 449 

77.  Examples  of  profile  and  cross-sections  of  earthwork  452 

78.  Cross-section  of  blind  drain 458 

79.  .    "  "   pole  drain 458 

80.  "  "    stone  drain 458 

81.  "  "  tile  drain 458 

82.  Protection  ordrain-outlet 458 

83,84.  Silt-basins 458 

85-89.  Examples  of  the  drainage  of  country  highways 461 

90.  Section  of  country  highway  , 463 

91.  Drainage  of  road  in  embankment 463 

92.  "         "  suburban  streets  463 

93-96.  Head-walls  for  pipe-culverts 468 

96«.  Wing  abutment  for  single  pipe-culvert 469 

96&.  Head- wall  for  double  pipe-culvert , 469 

96tf.  Head-wall  for  triple  pipe-culvert. 470 

96rf.  Section  of  pipe-culvert 470 

97-101.  Examples  of  box-culverts 473 

102-108.  Examples  of  arch-culverts 475,  477 

109-124.  Types  of  timber  bridges 482 

125-132.  Simple  timber  bridge 484,  485,  486 


LIST   OF    ILLUSTRATIONS.  XXV 

FIGURE  PAGE 

T32a.  Iron  swing-bridge 437 

1336,  132c.  Types  of  iron  bridges 488 

133-136.  Examples  of  retaining-walls 489 

137-139.  "          "  road  construction  along  the  seashore  or  margin  of 

rivers 494,  495 

140.  Examples  of  mound  and  ditcli  fence 496 

141,  142.  Arrangement  of  city  streets ,  502,  503.  505 

143,  144.  "  "  street-intersections 509,  510 

145.  Crowns  in  street  gutters 512 

146-148.  Arrangement  of  streets  with  opposite  sides  at  different  levels.  512,  513 

140.  Sub-foundation  drainage  of  streets  514 

150-153.  Examples  of  catch-basins 515,  516 

153«.  Examples  of  sewer  inlet , 519 

1536.   Sewer  inlet  without  basin 520 

154,  155.  Surface-drainage  at  street-intersection 521 

156.  Objectionable  form  of  water-way  at  street  crossings 521 

157.  Street  monument 522 

158.  159.  Example  of  widening  carriageway  at  street-intersections 524 

160.  Improper  method  of  dressing  flag-  and  bridge-stones 529 

161.  Drainage  of  park  walks 554 

162-166.  Fire-clay  curb 566 

167.  Iron  curb , 566 

168.  Granite  curb,  Washington,  D.  C 568 

169.  Bluestone  curb 568 

170.  171.  Hollow  curb 570 

172.  Arrangement  of  gutter-stones 571 

173-176.  Examples  of  crossings  and  gutters 574,  575 

177.  Tree-protection.. . .   651 

178.  Setting  slope-stakes 652 

179.  "      out  culverts  on  horizontal  ground 653 

180.  181.  Setting  out  culverts  on  sloping  ground 654 

182.  Setting  out  vertical  curves 656 

183.  ' '       stakes  for  street  contours 657 

184.  "  "      "   curb 657 

185.  "  "       "    any  structure 658 

186.  Bush-hooks ....710 

187.  Axe  mattock '710 

188.  Pick  mattock 710 

189.  Grading-pick 711 

190.  Clay-pick ' 711 

191.  Shovels 711 

192.  Grading-plough 71 2 

193.  Hardpan-plough 712 

194.  195.  Drag-scraper 713 

196.  Pole-scraper 714 


XX vi  LIST   OF   ILLUSTKATIOUSo 

KIGL'RK  PAGE 

197-199.  Wheeled  scraper 715 

200-202.  Wheelbarrows 716 

203.  Earth-cart 717 

204,  205.  Dump-cars 718,  719 

306,  207.  Dump- wagon 721 

208-210.  Mechanical  graders  or  road  machines 722,  723 

211,  212.  New  Era  grader 724 

213.  Surface-grader 726- 

214.  Road-leveller 726 

215.  Draining-tools. T27 

216.  Hand-drilling  tools 729 

217.  Steam-drill 731 

218.  Portable  boiler 733 

219.  Straight-edge 734 

220.  Roadbed- roller. 735 

221.  Sprinkling-cart 735 

222-233.  Stone-crushers 740-745 

234.  Stone-screen  746 

235,  236.  Engines  and  boilers 747,  748- 

237-241.  Stone-crushing  plants 749-751 

242.  Stone-distributing  cart 25'> 

243-246.  Horse-rollers 252-254 

247-251.  Steam-rollers 757-760 

252-254.  Paving-hammers • 76! 

255-259.  Paving-rammers 762 

260.  Asphalt  rammers 762 

261.  Asphalt  smoothing-iron , 762 

262.  Fire-pot  roller 763 

263.  Portable  fire-box 763 

264.  265.  Steam-rollers  for  asphalt 764 

266.  Asphalt-mixing  machine 765 

267.  Surface-heater  for  asphalt 766 

268.  269.  Concrete-mixing  machines 767,  768 

270.  Sand-dryer 7K9 

271.  Portable  heater  for  asphalt 76& 

272-276.  Sweeping-machines 770-772 

277.  Scraping-machine 775 

278-280.  Patrol-cart 774,  775 

281.  Hand-scoop 775 

282.  Hand-sweeper 776 

283.  Dump-cart 776 

284-286.  Combined  sweeping-and  collecting-machines 777-779 

287,  2886.  Street-sprinklers 780,  782 

289,  290.  Snow-ploughs 783 

291-297.  Tools  for  artificial  stone  pavements 784 


LIST   OF   ILLUSTRATIONS.  XXVJi 

FIGURE  PAGE 

298.  Iron  catch-basin 785 

299-300.  Gutter-gratings 786 

301.  Sewer  inlet-trap 787 

302,  303.  Inlet  for  broken-stone  roads 787 

304,  305.  Gutter  crossing 788 

306.  Gutter  boxes. .  .789 


s 


INTRODUCTION. 


HISTORICAL  SKETCH. 

ROADS  are  pathways  formed  through  a  country  to  facilitate  the 
movement  of  persons  and  exchange  of  commodities.  They  are  of 
various  kinds,  according  to  the  state  of  civilization  and  wealth  of 
the  country  traversed;  thus,  they  range  from  rude  paths,  passable 
only  by  pedestrians,  to  the  comparatively  perfect  modern  road, 
passable  alike  by  persons  and  vehicles. 

The  motive  for  the  formation  of  roads  is  found  (1)  in  the  in- 
quisitive spirit  of  man,  and  his  desire  for  intercourse  with  his  fel- 
lows; (2)  in  the  necessity  of  obtaining  provisions  for  his  sustenance 
in  times  of  scarcity;  and  (3)  in  the  desire  to  gratify  hi-  fancies 
with  the  products  of  other  localities. 

With  the  progress  of  civilization  and  the  congregation  of  men 
in  cities  and  towns  their  wants  multiply,  and  the  products  of  the 
earth  have  to  be  collected  and  transported  to  supply  them.  Th!« 
collecting,  transporting,  and  exchanging  of  products  is  trade  or 
commerce,  and  its  importance  and  expansion  are  directly  propor- 
tional to  the  facilities  afforded. 

Countries  inhabited  by  the  least  civilized  people  whose  wants 
are  supplied  by  nature  in  the  immediate  vicinity  of  their  dwellings 
are  almost  destitute  of  roads;  hence  it  has  come  to  be  said  that 
roads  are  the  physical  symbol  by  which  to  measure  the  progress  of 
any  age  or  people.  "  If  the  community  is  stagnant,  the  condition 
of  the  roads  will  indicate  the  fact ;  if  they  have  no  roads,  they  are 
savages." 

Although  roads  are  the  offspring  of  civilization,  they  have  be- 

xxix 


XXX  HIGHWAY  CO NS1  RUCTION. 

come  the  chief  factors,  if  not  indeed  the  means,  for  its  advancement. 
Without  them  the  invention  of  printing  and  other  arts  so  beneficial 
to  the  welfare  of  men  would  separately  be  ineffectual,  or  productive 
of  advantages  of  a  very  limited  extent.  Without  roads,  the  inter- 
change of  advantages,  moral,  intellectual,  and  physical,  which  now 
takes  place  in  all  highly  civilized  countries  between  the  rural  and 
urban  population,  could  not  be  maintained;  without  them,  indeed, 
large  towns  or  cities  could  not  continue  to  exist.  The  supply  of 
the  population  collected  in  such  places,  with  the  various  products 
of  agriculture  necessary  to  their  physical  existence,  could  not  be 
sustained.  Nor,  on  the  other  hand,  would  the  rural  population 
.affording  that  supply  be  benefited  by  a  return  in  exchange  of  the 
refinements  of  the  town,  and  the  various  articles  of  luxury  and 
necessity  obtained  by  commerce  from  every  part  of  the  globe. 

It  is  frequently  asserted  that,  since  the  introduction  and  de- 
yelopment  of  railroads,  the  latter  have  assumed  to  a  greater  and 
greater  degree  the  functions  of  the  common. road,  and  that  high- 
ways are  no  longer  an  indication  of  progress.  This  is  true  to  only 
a  limited  extent.  Railroads  have  changed  the  character  of  the 
traffic  on  the  common  roads,  and  personal  travel  for  business1 
or  pleasure  is  no  longer  dependent  upon  the  condition  of  the  high- 
ways; but  commercial  intercourse  as  represented  in  the  exchange 
of  products  is  as  much  dependent  upon  the  condition  of  the  public 
road  to-day  as  it  ever  was,  for  the  reason  that  it  is  impossible  to 
construct  a  railroad  to  the  door  of  each  producer  and  consumer. 
Hence  railroads  never  can  supersede  the  common  road,  and  every 
ton  of  freight  carried  by  them  must  be  conveyed  over  a  highway 
at  either  or  both  terminals,  and  the  cost  of  this  highway  transpor- 
tation has  a  marked  influence  not  alone  upon  the  price  paid  by  the 
consumer,  but  also  on  the  profit  realized  by  the  producer. 

If  railroads  may  be  compared  to  the  arteries  of  a  living  body, 
then  the  common  roads  are  the  veins,  and  each  is  equally  neces- 
sary in  quickening  and  communicating  life  to  the  parts  to  which 
they  lead.  But  the  true  relation  between  railroads  and  wagon-roads 
frequently  seems  to  be  lost  sight  of;  the  functions  of  each  are  quite 
different  and  in  no  sense  rivals.  The  highway  serves  the  very 
important  purpose  of  effecting  local  intercourse  and  of  connect- 
ing the  local  freight  and  passenger  traffic  with  the  railroad  service. 
Heads  running  parallel  to  the  railroad  and  connecting  towns  al- 


HISTORICAL   SKETCH.  XXXJ 


Teady  joined  by  the  railroad  are  of  but  little  importance,  It  is  the 
roads  running  at  an  angle  with  the  railroad  and  connecting  it  with 
the  country  to  the  right  and  left,  thus  acting  as  feeders,  that  re- 
quire attention  in  modern  times.  In  Baden,  Germany,  this  rela- 
tion of  the  roads  to  the  railroads  was  early  recognized  by  striking 
from  the  list  of  state  roads  all  those  that  ran  parallel  to  the  rail- 
road or  had  lost  their  importance  by  its  construction,  in  order  to 
save  funds  for  the  support  of  the  others;  while  most  of  those  run- 
ning across  the  railroad,  if  they  crossed  at  a  station  so  that  they 
served  as  feeders,  were  raised  to  the  grade  of  state  roads. 

The  word  "  road  "  is  derived  from  the  Anglo-Saxon  rad,  a  riding, 
and  ridan,  to  ride,  and  as  generally  used  it  means  a  public  high- 
way, although,  as  a  generic  term,  it  is  applied  to  any  kind  of  a 
path  open  to  travel. 

The  word  "  highway  "  is  probably  the  more  correct  term  when 
applied  to  a  traveled  thoroughfare,  but  custom  has  established  the 
propriety  of  using  the  word  "  road/' 

The  word  "  highway  "  is  used  several  times  in  the  Old  Testa- 
ment, while  the  word  "road  "  is  used  but  once. 

As  to  when  paved  roads  were  first  introduced  little  is  known; 
we  find  here  and  there  in  the  works  of  the  ancient  historians  occa- 
sional mention  of  road  construction.  Herodotus  speaks  of  a  great 
Egyptian  road,  constructed  under  King  Cheops,  upon  whicli 
100,000  men  were  employed  for  ten  years.  Strabo  informs  us  that 
the  city  of  Babylon  was  paved  about  the  year  2000  B.C.,  and  that 
three  great  highways  ran  from  there  to  Suza,  Ecbatana,  and  Sardes. 
The  highway  loading  from  Babylon  to  Memphis  was  paved  at  an 
early  date,  and  along  it  arose  the  cities  of  Nineveh,  Palmyra, 
Damascus,  Tyre,  Antioch,  and  other  great  commercial  cities. 

The  importance  of  roads  to  the  welfare  of  nations  was  not 
unknown  to  the  ancients.  The  senate  of  Athens,  the  governments 
of  Lacedaemon,  Thebes,  and  other  states  of  Greece,  bestowed  much 
care  upon  them.  The  Carthaginians  were  systematic  and  scientific 
road-makers;  they  built  up  and  consolidated  an  empire  so  promi- 
nent in  military  and  naval  achievements  and  in  the  arts  and 
industries  of  civilized  life  that  for  four  hundred  years  it  was 
able  to  hold  its  own  against  the  preponderance  of  Greece  and 
Rome. 


XXX11  HIGHWAY    CONSTRUCTION. 

The  Romans  learned  the  art  of  making  paved  roads  from  the 
Carthaginians,  and  the  highways  constructed  by  them  are  great 
monuments  in  this  department  of  art. 

The  first  Roman  road  was  constructed  under  the  direction  of 
the  censor  Appius  Claudius  (312  B.C.).  This  road,  named  after  him 
the  Appian  Way,  was  frequently,  on  account  of  its  excellence,  called 
the  "  queen  of  roads."  Under  Augustus  and  Julius  Caesar  the 
Roman  capital  was  made  to  communicate  with  all  the  chief  towns 
by  paved  roadways,  and  during  the  last  African  war  a  road  of  this 
kind  was  constructed  from  Spain  through  Gaul  to  the  Alps. 
Later  these  great  lines  of  communication  were  extended  through 
Savoy,  Dauphine,  and  Provence ;  through  Germany,  every  part  of 
Spain,  through  Gaul,  and  even  to  Constantinople ;  through  Hungary, 
Macedonia,  and  to  the  mouths  of  the  Danube.  Neither  did  the  in- 
terposition of  seas  obstruct  the  labor  or  daunt  the  enterprise  of  this 
great  people.  The  lines  of  communication  thus  constructed  to  the 
shores  of  the  continent  of  Europe  were  continued  at  corresponding 
points  of  the  neighboring  islands  and  continents.  Sicily,  Corsica, 
Sardinia,  England,  Africa,  and  Asia  were  accordingly  penetrated 
and  intersected  by  roads,  forming  the  continuation  of  the  great 
European  lines.  These  gigantic  works  were  the  most  solid  struc- 
tures of  their  kind  which  have  been  formed  in  any  age,  and  many 
of  them  still  remain,  often  forming  the  foundation  of  modern  roads 
and  in  some  instances  constituting  the  road-surface  now  used. 
From  these  remains  and  the  accounts  of  ancient  writers  we  are  en- 
abled to  follow  the  methods  employed  in  their  construction.  The 
engineering  appears  to  have  been  very  simple.  A  prominent  land- 
mark was  selected  in  the  direction  desired,  and  the  road  located  on 
an  absolute  straight  line  without  reference  to  intervening  obstacles. 

The  roads  were  divided  into  two  classes:  (1)  Private  roads,  the 
use  of  which  was  free,  while  the  soil  remained  private  property; 
and  (2)  public  roads,  of  which  the  use,  the  management,  and  the 
soil  itself  were  alike  vested  in  the  state.  The  public  roads  were 
divided  into  three  classes.  The  military  roads  were  called  "prae- 
torian roads,"  being  under  the  immediate  government  of  praetors, 
or  military  superiors.  The  high  roads  were  called  "consular 
roads,"  because  they  were  made  and  maintained  by  the  authority 
of  the  consuls;  and  the  local  roads  leading  from  the  consular  roads 
to  small  places  were  called  "  vicinal  roads."  The  width  of  the 


HISTORICAL    SKETCH.  XXXiii 


roads  varied  from  8  to  20  feet,  and  the  method  of  construction  was 
as  follows :  Two  shallow  trenches,  called  sulci,  were  first  dug  par- 
allel to  each  other,  marking  the  width  of  the  road.  The  space 
between  them  was  excavated  to  solid  ground;  in  this  excavation 
the  road  materials  were  placed,  arranged  in  four  layers  having  a 
total  thickness  of  about  three  feet:  (1)  The  statumen,  or  founda- 
tion, consisting  of  two  courses  of  large  flat  stones  laid  in  lime-mor- 
tar, or  of  stones  not  smaller  than  the  hand  could  grasp;  (2)  The 
rudus,  composed  of  broken  stones  mixed  with  one  third  their 
quantity  of  lime-mortar,  and  forming  a  layer  about  9  inches  in 
thickness;  (3)  The  nucleus,  composed  of  fragments  of  brick,  stones, 
and  pottery,  set  in  lime-mortar,  and  about  6  inches  thick;  (4)  The 
summa  crusta,  or pavimenhtm,  composed  of  large  irregularly  shaped 
stones  about  6  inches  thick,  closely  jointed  and  fitted  with  the 
utmost  nicety.  These  roads  bore  uninjured  the  weight  of  columns, 
obelisks,  and  other  immense  blocks  of  stone  weighing  hundreds  of 
tons;  notwithstanding  this,  the  utmost  weight  which  each  class  of 
vehicle  was  permitted  to  carry  was  regulated  by  law,  and  those 
laws  were  strictly  enforced.  Although  these  roads  were  eminently 
durable,  they  were  deficient  in  the  other  qualities  requisite  for  a 
good  road,  and  Horace  states  that  they  were  "less  fatiguing  to 
people  who  travel  slowly." 

Streets  were  paved  with  large  polygonal  blocks,  laid  as  described 
above,  and  footways  with  rectangular  slabs.  Specimens  are  still  to 
be  seen  in  Rome  and  Pompeii. 

The  curator  viarum  of  the  Romans  was  an  official  of  distinc- 
tion, wielding  great  authority,  and  Plutarch  tells  us  of  Caius 
Gracchus  that  when  he  was  appointed  supreme  director  for 
making  roads,  the  people  were  charmed  to  see  him  go  forth  on  his 
tours  of  road-making  followed  by  such  numbers  of  ambassadors, 
magistrates,  architects,  and  artificers. 

When  the  Romans  conquered  Gaul  they  found  many  roads  or 
trails  from  three  to  six  feet  wide,  and  the  French  archaeologists 
tell  us  that  nearly  13,000  miles  of  these  trails  were  improved  by 
the  invaders. 

In  Peru  the  Incas  built  great  roads,  the  remains  of  which  attest 
their  magnificence.  Humboldt  in  his  "  Aspects  of  Nature  "  speaks 
of  the  mountain  road  from  Quito  to  Cuzco  as  "  a  marvellous  work, 
not  inferior  to  the  most  imposing  Roman  roadways."  It  was  from 


XXXIV  HIGHWAY   CONSTRUCTION. 

1500  to  2000  miles  in  length,  and  most  of  it  was  at  an  elevation  of 
over  12,000  feet  above  the  level  of  the  sea;  it  was  20  feet  wide  and 
paved  with  stones  10  feet  square,  and  had  a  running  stream  and  a 
row  of  shade-trees  on  each  side.  Prescott  in  his  "History  of 
Peru,"  in  speaking  of  this  road,  says  that  "  it  was  conducted  over 
sierras  covered  with  snow;  galleries  were  cut  through  the  living 
rock ;  rivers  were  crossed  by  means  of  bridges  swung  suspended  in 
the  air;  precipices  were  scaled  by  stairways  hewn  out  of  the  native 
bed,  and  ravines  of  hideous  depth  were  filled  up  with  solid 
masonry." 

In  the  breaking-up  of  society  which  followed  the  decline  of  the 
Roman  Empire,  the  roads  fell  out  of  repair  and  finally  into  ruin. 
During  the  Dark  Ages  they  were  regarded  with  terror  as  aids  to 
plunder,  and  such  intercourse  as  was  maintained  took  place  almost 
exclusively  by  rude  paths  capable  of  being  passed  on  foot,  or  at  best 
by  horses.  With  the  reconstruction  of  society  in  Europe  the  roads 
gradually  became  practicable  for  pack-animals  and  the  rude  vehicles 
of  the  time;  but  no  serious  attempt  was  made  to  restore  or  replace 
the  public  highways  until  the  middle  of  the  eighteenth  century. 
About  this  time  the  revival  of  road  construction  was  almost  simul- 
taneous in  England  and  France,  and  shortly  afterwards  the  other 
chief  countries  of  Europe  took  up  the  matter. 

Among  the  first  laws  passed  in  England  on  the  subject  of 
roads  is  one  in  the  year  1285,  directing  that  all  bushes  and  trees 
along  the  roads  leading  from  one  market  to  another  should  be  cut 
down  for  200  feet  on  either  side,  to  prevent  robbers  lurking  therein, 
and  providing  "  that  when  any  highway  is  worn  deep  and  incom- 
modious that  another  shall  be  laid  out  alongside."  Henry  VIII. 
also  made  provision  under  this  head  by  enacting  "that  two  justices 
of  the  peace  and  twelve  other  men  of  wisdom  and  discretion  shall 
choose  fresh  routes  when  the  old  ones  are  worn  out."  In  1346 
Edward  III.  authorized  the  first  toll  to  be  levied  for  the  repair  of 
the  roads.  In  1523  the  English  Parliament  passed  the  first  act 
relative  to  the  improvement  of  the  public  roads. 

Regarding  the  condition  of  the  English  highways  a  hundred 
and  fifty  years  ago,  Lord  Macaulay  tells  us  that  it  was  no  uncom- 
mon thing  for  the  fruits  of  the  earth  to  rot  in  one  place  when  a  score 
of  miles  away  the  people  were  suffering  from  a  scarcity  of  the  very 
food  which  was  spoiling  and  almost  within  their  reach.  The  roads 


HISTORICAL    SKETCH.  XXXV 


were  so  wretched  that  the  food  could  not  be  transported.  At  this 
time  each  parish  was  obliged  to  build  and  maintain  the  roads 
within  its  confines,  and  it  not  infrequently  happened  that  a  poor 
and  impoverished  agricultural  community  was  expected  to  maintaiq 
a  highway  between  two  rich  and  prosperous  towns. 

Mr.  Arthur  Young  in  his  "  Six  Months'  Tour  in  the  North  of 
England  "  gives  us  the  following  account  of  the  state  of  the  roads 
at  that  time  (1770) :  "'I  know  not  in  the  whole  range  of  language 
terms  sufficiently  expressive  to  describe  this  infernal  road.  Let  me 
most  seriously  caution  all  travellers  who  may  accidentally  propose  to 
travel  this  terrible  country  to  avoid  it  as  they  would  the  devil;  for 
a  thousand  to  one  they  break  their  necks  or  their  limbs,  by  over- 
throws or  breaking-downs.  They  will  here  meet  with  ruts,  which 
I  measured,  actually  four  feet  deep,  and  floating  with  mud  only 
from  a  wet  summer.  What,  therefore,  must  it  be  after  a  winter  ? 
The  only  mending  it  receives  is  tumbling  in  some  loose  stones, 
which  serve  no  other  purpose  than  jolting  a  carriage  in  the  most 
intolerable  manner.  These  are  not  merely  opinions,  but  facts;  for 
I  actually  passed  three  carts  broken  down  in  these  eighteen  miles 
of  execrable  memory." 

England  sought  to  improve  the  ill-condition  of  her  highways  by 
the  establishment  of  a  comprehensive  system  of  turnpikes,  and  be- 
fore the  beginning  of  this  century  thirty  thousand  miles  of  these 
roads  had  been  built;  but  they  were  constructed  in  such  an  imper- 
fect manner  that  they  were  but  little  improvement  on  the  old 
roads.  Even  as  late  as  1809  the  roads  answered  the  description  of 
Mr.  Young,  and  little  improvement  was  effected  till  the  advent  of 
MacAdam  and  Telford.  Contemporaries  and  in  some  respects  ad- 
vocates of  rival  systems,  to  these  two  men  England  owes  her 
present  admirable  system  of  roads;  and  Charles  Dickens  wrote: 
"  Our  shops,  our  horses'  legs,  our  boots,  our  hearts,  have  all  been 
benefited  by  the  introduction  of  MacAdam/' 

The  French  and  the  Swiss  probably  have  the  best  highways  of 
any  of  the  European  countries.  Until  the  time  of  Louis  XIV.  the 
roads  of  France  received  no  more  attention  than  did  those  of  Eng- 
land. This  monarch  had  several  fine  roads  made  in  the  environs  of 
Paris  for  his  personal  use  and  pleasure.  They  were  very  wide  and 
paved  only  in  the  centre.  Shortly  after  the  construction  of  these 
royal  roads  the  nation  began  tc  appreciate  the  advantage  of  good 


XXX  VI  HIGHWAY    CONSTRUCTION. 

roads,  but  it  was  not  until  the  advent  of  the  first  Napoleon  that  the 
modern  system  of  magnificent  highways  was  inaugurated,  solely  for 
military  purposes,  and  this  object  has  never  been  lost  sight  of  ;  so 
that,  although  in  modern  times  their  use  as  a  means  of  communica- 
tion for  the  people  accounts  for  their  great  and  increasing  number, 
it  is  largely  owing  to  their  military  character  that  the  French  gov- 
ernment expends  the  enormous  sums  it  does  annually  on  the 
national  roads. 

The  material  and  financial  prosperity,  thriftiness,  and  content- 
ment of  the  French  people  has  long  excited  the  admiration  of  the 
world;  neither  internal  revolution  nor  defeat  from  abroad  appears 
to  have  entailed  upon  them  burdens  too  heavy  for  them  to  bear. 
Students  of  economic  problems  ascribe  this  marvellous  condition  to 
the  far-reaching  and  splendidly  maintained  system  of  highways,  on 
which  the  obstacles  to  economical  transportation  have  been  reduced 
to  the  minimum. 

In  the  United  States  the  highways  have  not  improved  as  rapidly 
as  other  institutions;  in  fact,  they  are  very  inferior  to  those  of 
Europe.  The  reason  for  this  may  be  attributed  to  several  causes, 
among  which  may  be  mentioned  (1)  the  excellence  of  the  railroad 
systems  and  waterways;  (2)  the  indifference  of  those  in  charge  of 
highway  maintenance;  (3)  the  want  of  appreciation  of  the  benefits 
of  good  roads  and  the  fear  of  increased  taxation  on  the  part  of  the 
rural  population;  (4)  the  dispersion  of  the  people  over  large 
areas  in  their  search  for  desirable  localities  for  residence;  and  (5) 
the  ill-effects  of  the  system  requiring  the  personal  service  of  the 
rural  population  on  the  highways. 

The  experience  of  Europe  iu  road  improvement  shows  that  the 
highways  should  be  taken  as  much  as  possible  out  of  the  hands  of 
local  authorities,  and  administered  by  either  national  or  state  gov- 
ernments in  accordance  with  the  needs  of  the  people  who  use  the 
roads;  and  that  as  the  whole  public  is  benefited  by  good  roads, 
therefore  all  should  pay  for  their  improvement  and  maintenance. 
This  view  of  the  subject  is  not  new  in  the  United  States,  for  Wash- 
ington recommended  in  a  letter  to  Patrick  Henry  that  the  roads 
of  Virginia  be  taken  away  from  the  control  of  the  county  courts 
and  be  given  to  the  State  authorities.  One  of  Hamilton's  pet 
schemes  was  that  of  road  improvement,  and  he  recognized  thor- 
oughly that  roads  left  to  local  authority  would  never  be  satisfac- 


HISTORICAL    SKETCH.  XXX vii 


torily  built.  During  the  past  ninety  years  there  has  been  more  or 
less  national  legislation  in  'regard  to  coin  in  on  roads.  Several  very 
comprehensive  measures  have  passed  one  or  another  of  the  Houses 
of  the  National  Congress,  but  the  only  road  of  any  consequence 
constructed  by  the  government  was  the  national  road  (650|  miles  in 
length,  80  feet  in  width,  and  macadamized  for  a  width  of  30  feet), 
which  it  originally  was  intended  should  go  from  the  tide-water  of  the 
A  lilantic  Ocean  to  the  Ohio  Eiver.  It  was  built  from  Cumberland 
in  Maryland  to  a  point  in  Ohio  several  hundred  miles  from  the 
Ohio  River,  and  there  it  was  allowed  to  stop,  being  finally  donated 
to  the  States  through  which  it  passes.  In  this  way  ended  the  first 
great  effort  of  the  Federal  Government  to  build  and  establish,  as  the 
Constitution  of  the  United  States  contemplated,  a  system  of  post- 
roads  all  over  the  country. 

The  date  of  the  first  introduction  of  street  pavements  cannot  be 
determined  with  certainty.  Livy  informs  us  that  in  the  year  584 
(about  170  B.C.  )  the  censors  caused  the  streets  of  Rome  to  be  paved 
from  the  ox  market  to  the  temple  of  Venus.  Streets  paved  with  lava, 
having  deep  ruts  worn  by  the  wheels  of  chariots,  and  raised  banks 
on  each  side  for  foot-passengers,  are  found  at  Pompeii  and  Hercu- 
laneum. 

Abderahman,  the  caliph  of  Cordova,  Spain,  caused  the  streets  of 
that  city  to  be  solidly  paved,  A.H.  236  (A.D.  950),  and  a  man 
might  walk  after  sunset  ten  miles  in  a  straight  line  by  the  light  of 
the  public  lamps. 

The  earliest  reference  to  street  pavements  in  the  British  Isles 
is  found  in  the  records  of  the  city  of  Glasgow.  In  the  year  1577 
the  council  resolved  to  spend  £200,  "  to  big  the  calsayis,"  or,  to 
modernize  it  somewhat,  to  build  the  causeways. 

The  date  of  the  first  introduction  of  pavements  into  London  is 
unknown,  but  the  streets  of  that  city  were  not  paved  at  the  end  of 
the  eleventh  century.  It  is  related  that  in  the  year  1190  the 
chucch  of  St.  Mary-le-Bow  in  Cheapside  was  unroofed  by  a 
violent  wind,  and  that  four  pillars,  26  feet  in  length,  sunk  so  deep 
?.nto  the  ground  that  scarcely  4  feet  of  them  appeared  above  the 
surface  of  the  soft  earth  forming  the  street.  Holborn  was  first 
paved  in  1417,  and  Smithfield  in  1614.  The  first  act  for  paving 
and  improving  the  City  of  London  was  passed  in  1532.  The 
streets  were  described  in  the  simply- worded  statute  as  "very 


XXXvili  HIGHWAY   CONSTRUCTION. 

foul,  and  full  of  pits  and  sloughs,  so  as  to  be  mighty  perilous  and 
noyous,  as  well  for  all  the  king's  subjects  on  horseback  as  on  foot 
with  carriages"  (litters). 

The  capital  of  France  was  not  paved  in  the  twelfth  century,  for 
Rigord,  the  physician  and  historian  of  Philip  II.,  relates  that,  the 
king  standing  one  day  at  a  window  of  his  palace  near  the  Seine 
and  observing  that  the  carriages  which  passed  threw  up  the  dirt 
in  such  a  manner  that  it  produced  ^  most  offensive  stench,  his 
majesty  resolved  to  remedy  this  intolerable  nuisance  by  causing 
the  streets  to  be  paved,  which  was  accordingly  done.  The  orders 
for  this  purpose  were  issued  by  the  government  in -the  year  1184, 
and  upon  that  occasion,  it  is  said,  the  name  of  the  city,  which  was 
then  called  Lutetia,  on  account  of  its  dirtiness,  was  changed  to  that 
of  Paris. 

Dijon,  France,  had  paved  streets  as  early  as  1391,  and  it  is  re- 
marked by  historians  that  after  this  was  done  dangerous  diseases, 
such  as  dysentery,  spotted  fever,  and  others,  became  less  frequent 
in  that  city. 

In  the  United  States,  Boston,  Mass.,  appears  to  have  been  the 
first  city  to  pave  its  streets,  for  when  Josselyn  visited  that  city  in 
1663  he  found  many  streets  paved  with  pebbles;  and  AVard  said  in 
1699:  "  The  buildings,  like  their  women,  being  neat  and  handsome, 
and  their  streets,  like  the  hearts  of  the  male  inhabitants,  are  paved 
with  pebble."  Drake  says  that  the  paving  of  the  public  streets 
began  very  early  and  was  made  of  importance  after  1700;  the  side- 
walks were  also  early  paved  with  cobblestones  and  flags. 

We  learn  that  the  first  regular  paving  of  a  Philadelphia  street 
was  due  to  an  accident.  A  man  on  horseback  being  mired  and 
thrown  from  his  horse,  breaking  his  leg,  a  subscription  was  raised 
and  the  street  paved  with  pebbles  from  the  river-bank.  In  1719 
many  sidewalks  were  being  paved  with  brick  and  the  cartway  with 
cobblestone. 

In  1750  the  grand  jury  represented  the  great  need  of  paved 
streets,  "so  as  to  remedy  the  extreme  dirtiness  and  miry  state  of 
the  streets;"  but  the  first  general  effort  worthy  of  mention  to  pave 
the  streets  was  made  in  1761-62,  and  then  the  only  means  applied 
to  the  purpose  was  that  produced  by  lotteries. 

In  New  York  City  the  first  stone  pavement  appears   to  have 


HISTORICAL    SKETCH.  XXxix 


been  laid  in  about  the  year  1657  on  Brower  Street,  between  Broad 
and  Whitehall,  and  known  to-day  as  Stone  Street. 

The  division  of  streets  into  carriageways  and  footways  appears 
to  have  been  first  practised  in  1614,  in  which  year  the  citizens  of 
London  began  to  pave  the  margins  of  the  streets  before  their 
doors,  but  the  middle  of  the  streets  was  paved  with  large  pebbles 
very  unevenly.  In  1761  raised  footways  of  square  granite  blocks 
were  used  in  Westminster  and  for  London  generally  in  1766. 

In  1704  the  Common  Council  of  Albany,  N.  Y.,  ordered  "that 
ye  streets  be  paved  before  each  inhabitant's  door  within  this  city, 
eight  foot  breadth  from  their  houses  and  lotts,  before  ye  25th 
of  October  next  ensuing,  upon  penalty  of  forfeiting  the  summe  of 
15  shillings  for  ye  Behooffe  of  ye  sheriffe,  who  is  to  sue  for 
ye  same/' 

In  New  York  the  first  footwalks  were  laid  in  1790,  on  the  west 
side  of  Broadway,  from  Vesey  to  Murray  Street,  and  opposite  for 
the  same  distance  along  the  Bridewell  fence.  They  were  narrow 
pavements  of  brick  and  stone,  scarcely  wide  enough  to  permit  two 
persons  to  walk  abreast. 

In  1696  the  first  contract  for  cleaning  the  streets  of  New  York 
was  made.  Prior  to  this  the  work  had  been  done  by  the  citizens, 
every  man  being  required  to  keep  the  street  clean  before  his  door. 

In  1697  the  first  attempt  at  lighting  the  streets  of  New  York 
was  made.  This  was  done  by  hanging  out  a  lantern  with  a  candle 
in  it  upon  the  end  of  a  pole  from  the  window  of  every  seventh 
house  on  the  nights  when  there  was  no  moon,  the  expense  being 
divided  equally  among  the  several  houses. 

Authority  to  construct  toll-roads  was  first  granted  in  England, 
in  1346,  but  their  construction  did  not  become  general  until  1676, 
and  they  were  entirely  abolished  in  1878. 

In  the  United  States  the  first  toll-road  company  was  incorpo- 
rated in  Pennsylania  in  1792,  to  construct  and  maintain  an 
artificial  road  from  Philadelphia  to  Lancaster,  a  distance  of  about 
70  miles.  The  framers  of  the  act  authorizing  the  construction  of 
this  road  recognized  the  importance  of  the  relation  between  tho 
load  and  the  width  of  the  wheel-tire.  The  rate  of  toll  was  graded 
according  to  the  width  of  the  tire,  and  the  maximum  load  to  te 
carried  by  the  different  widths  of  tire  was  distinctly  stated. 
Vehicles  with  tires  of  less  breadth  than  four  inches  were  not 


xl  HIGHWAY    CONSTRUCTION. 

allowed  to  carry  more  than  two  and  a  half  .tons  between  the  first 
day  of  December  and  the  first  day  of  May,  and  not  more  than  three 
tons  during  the  rest  of  the  year. 

The  act  also  provided  for  the  placing  of  milestones  and  the 
erection  of  guide-posts  at  all  intersecting  roads,  with  the  name  of 
the  place  to  which  they  led  and  its  approximate  distance  in  miles. 

Though  considerable  advance  in  processes  and  machines  have 
been  made  during  the  past  hundred  years,  the  two  chief  factors  in 
the  preservation  of  roads  so  ably  regulated  in  the  above  mentioned 
•act  are  still  the  same,  and  in  many  cases  are  the  cause  of  the  evils 
we  suffer  from  in  the  shape  of  bad  highways. 


A  TREATISE  ON  HIGHWAY  CONSTRUCTION, 


CHAPTER  I. 
PAVEMENTS. 

1.  General  Considerations. — The  object  of  a  pavement  is  (1)  to 
secure  a  water-tight  covering  that  will  preserve  the  natural  soil 
from  the  effects  of  moisture,  and  not,  as  commonly  supposed,  to 
support  the  vehicles,  the  weight  of  which  and  tha';  of  the  covering 
material  must  be  actually  borne  by  the  natural  soil.     (2)  To  fur- 
nish a  smooth  surface  on  which  the   force   of  traction   will   be 
reduced  to  the  least  possible  amount,  and  over  which  vehicles  may 
pass  with  safety  and  expedition  at  all  seasons  of  the  year. 

2.  The  dualities  essential  to  a  good  pavement  may  be  stated  as 
follows : 

(1)  It  should  be  impervious. 

(2)  It  should  afford  good  foothold  for  horses. 

(3)  It  should  be  hard  and  durable,  so  as  to  resist  wear  and  dis- 
integration. 

(4)  It  should  be  adapted  to  every  grade. 

(5)  It  should  suit  every  class  of  traffic. 

(6)  It  should  offer  the  minimum  resistance  to  traction. 

(7)  It  should  be  noiseless. 

(8)  It  should  yield  neither  dust  nor  mud. 

(9)  It  should  be  easily  cleaned. 

(10)  It  should  be  cheap. 


HIGHWAY    CONSTRUCTION. 


3.  Interests  affected  in  the  Selection. — Of  the  above  require- 
ments, numbers  2,  4,  5,  and  6  affect  the  traffic  and  determine  the- 
cost  of  haulage  by  the  limitations  of  loads,  speed,  wear  and  tear  of 
horses  and  vehicles.     If  the  surface  is  rough  or  the  foothold  bad, 
the  weight  of  the  load  a  horse  can  draw  is  decreased,  thus  necessi- 
tating the  making  of  more  trips  or  the  employment  of  more  horses 
and  vehicles  to  move  a  given  weight.     A  defective  surface  necessi- 
tates a  reduction  in  the  speed  of  movement  and  consequent  loss 
of  time ;  it  increases  the  wear  of  horses,  thus  decreasing  their  life- 
service,  and  lessens  the  value  of  their  current  services;  it  also  in- 
creases the  cost  of  maintaining  vehicles  and  harness. 

Numbers  7,  8,  and  9  affect  the  occupiers  of  the  adjacent  premises, 
who  suffer  from  the  effect  of  dust  and  noise;  and  second,  the  own- 
ers of  said  premises,  whose  income  from  rents  is  diminished  where 
these  disadvantages  exist. 

Numbers  3  and  10  affect  the  taxpayers  alone,  first  as  to  the  length 
of  time  during  which  the  covering  remains  serviceable,  and  second 
as  to  the  amount  of  the  annual  repairs.  Number  1  affects  the 
adjacent  occupiers  principally  on  hygienic  grounds.  Numbers  7 
and  8  affect  both  traffic  and  occupiers. 

4.  Selection  of  Pavements. — In  the  selecting  of  the  most  suita- 
ble pavement,  whether  for  a  street  or  a  country  road,  all  classes  of 
citizens  are  alike  interested;  for  of  all  the  systems  of  intercom- 
munication none  is  brought  into  more  direct  contact  with  the  peo- 
ple than   the  public  highway,  and  its  effect  upon  the  price  of 
commodities  is  felt  by  all.     Not  a  ton  of  agricultural  or  mechani- 
cal produce  can  reach  its  destination  without  first  and  last  paying 
toll  to  the  condition  of  the  highway  over  which  it  has  to  be  hauled; 
in  the  form  of  time,  wear  and  tear  of  horses,  harness,  and  vehicles 
thus  enhancing  its  cost  to  the   consumer  without  any  increased 
benefit  to  the  producer,  who  must  be  compensated  for  the  cost  of 
all  unnecessary  expenses  of  transportation  due  to  the  ill  condition 
of  the  highway. 

5.  Cost  of  Wagon  Transportation. — It  is  apparent  that  but  few 
people  comprehend  the  cost  of  transportation  by  horses  and  wagons, 
or  realize  the  amount  of  money  annually  wasted  by  the  ill  condi- 
tion of  the  roadways. 

Table  I  shows  from  actual  observation  the  cost  of  moving  a 
load  of  one  ton  a  distance  of  one  mile  on  level  roadways  with 


PAVEMENTS. 


different  pavements  in  the  usual  condition  in  which  they  are  main- 
tained. The  excessive  amount  of  these  charges  is  seen  when  it 
is  remembered  that  the  same  goods  using  the  roadways  are  now 
carried  by  the  railroads  at  an  average  cost  of  T6^  of  a  cent  per  ton- 
mile. 

TABLE  I. 

Cost  OF  TRANSPORTATION  BY  HORSES  AND  WAGONS   PER  TON-MILE  ON 
DIFFERENT  ROAD-COVERINGS. 

Iron  rails 1.28  cents  per  ton-mile 

Asphalt , 2.70 

Stone,  paving,  dry  and  in  good  order 5.33          "  " 

' '          "          ordinary  condition 12.00          "  " 

covered  with  mud 21.30          "  " 

Broken  stone,  dry  and  in  good  order 8.00          "  " 

moist     "     "        "      10.30 

ordinary  condition 11.90          "  " 

covered  with  mud 14.30          "  " 

"       ruts  and  mud 26.00 

Earth,  dry  and  hard 18.00 

ruts  and  mud 39.00 

Gravel,  loose 51.60 

compacted 12.80          "  " 

Plank,  good  condition 8.80          "  " 

Sand,  wet 32.60 

"      dry 64.00 

6.  In  1890  the  railroads  of  the  United  States  carried  over 
600,000,000  tons  of  freight.  Most  if  not  all  of  this  had  to  be  han- 
dled at  one  or  both  terminals  in  wagons.  If  the  distance  hauled 
was  but  one  mile  and  the  rate  per  ton-mile  22  J  cents,  which  is  the 
average  rate  of  haulage,  the  cost  would  be  $133,500,000.  The  low 
rate  of  railroad  transportation  has  been  achieved  by  careful  and 
scientific  study,  and  by  daily  attention  to  every  portion  of  the  road- 
bed and  rolling  stock.  Defective  parts  are  instantly  removed  and 
new  ones  substituted  so  that  the  road  is  always  in  good  order.  But 
pavements  once  laid  are  left  to  batter  the  vehicles,  and  the  vehi- 
cles, in  return,  to  pound  the  pavements:  little  or  no  attention 
being  paid  to  them  until  they  finally  become  unendurable  and  are 
entirely  renewed.  Moreover,  on  every  well-managed  railroad  the 
statistics  of  cost  of  transportation  are  the  subject  of  the  most  sci- 
entific study,  and  at  the  end  of  each  year  it  is  exactly  ascertained 


HIGHWAY    CONSTRUCTION. 


just  how  much  it  has  cost  to  haul  a  ton  of  freight  one  mile,  and 
what  proportion  of  this  is  for  train  service,  what  for  maintenance  of 
rolling  stock,  what  for  maintenance  of  way,  and  so  on;  whereas 
very  few  engineers  in  charge  of  highways  have  attempted  to  find 
out  accurately  what  is  the  relative  damage  done  to  vehicles  and 
horses  by  different  kinds  of  pavements,  what  is  the  relative  amount 
of  force  required  to  draw  a  unit  of  weight  on  different  surfaces, 
what  is  the  relative  cost  of  maintaining  different  pavements  during 
a  term  of  years  under  a  unit  of  traffic,  or  what  is  the  exact  propor- 
tion of  horses  falling  on  different  surfaces. 

7.  Effect  of  Reducing  the  Cost  of  Wagon  Transportion. — If  the 
cost  of  wagon  transportation  could  be  reduced  by  the  improvement 
of  the  highways  to,  say,  five  cents  per  ton-mile,  what  would  be  the 
result  ?     It  would  create  an  annual  saving  of  many  millions  of  dol- 
lars and  it  would  put  in  motion  a  large  tonnage  of  various  kinds  of 
merchandise  that  cannot  now  be  handled  with  profit ;  it  would  give 
a  large  margin  of  profit  on  many  products  which  are  now  moved 
with  little  profit,  and  would  directly  benefit  both  the  producer  and 
the  consumer. 

The  cost  of  wagon  transportation  over  the  roads  of  France  does 
not  exceed  one  third  the  like  expense  in  America,  it  being  common 
in  rural  districts  to  haul  three  tons  and  in  the  cities  from  three  to 
five  tons  net  freight  with  one  horse. 

8.  Problem  involved  in  the  Selection  of  Pavements. — The  prob- 
lem involved  in  the  selection  of  the  most  suitable  pavement  is 
composed  of   the   following  factors:    first,  adaptability;    second, 
desirability;  third,  serviceability;  fourth,  durability;  fifth,  cost. 

9.  Adaptability. — The  best  pavement  for  any  given  roadway 
will  depend  altogether  on  local  circumstances.     Pavements  must  be 
adapted  to  the  class  of  traffic  that  will  use  them.     The  pavement 
suitable  for  a  road  through  an  agricultural  district  will  not  be 
suitable  for  the  streets  of  a  manufacturing  centre,  nor  will  the 
covering  suitable  for  heavy  traffic  be  suitable  for  a  pleasure-drive 
or  a  residential  district. 

General  experience  indicates  the  relative  fitness  of  the  several 
materials  as  follows: 

For  country  roads,  suburban  streets,  and  pleasure-drives,  broken 
stone.  For  streets  having  heavy  and  constant  traffic,  rectangular 
blocks  of  stone  laid  on  a  concrete  foundation  with  the  joints  filled 


PAVEMENTS. 


with  bituminous  or  Portland  cement  grout.  For  streets  devoted 
to  retail  trade  and  where  comparative  noiselessness  is  essential, 
asphalt,  wood,  or  brick. 

10.  Desirability.— The  desirability  of  a  pavement  is  its  posses- 
sion of  qualities  which  make  it  satisfactory  to  the  people  using  and 
seeing  it.     Between  two  pavements  alike  in  cost  and  durability, 
people  will  have  preferences  arising  from  the  condition  of  their 
health,  personal  prejudices,  and  various  other  intangible  influences, 
causing  them  to  select  one  rather  than  the  other  in  their  respective 
streets.     Such  selections  are  often  made  against  the  demonstrated 
economies  of  the  case,  and  usually  in  ignorance  of  them.     When- 
ever one  kind  of  pavement  is  more  economical  and  satisfactory  to 
use  than  is  any  other,  there  should  not  be  any  diiference  of  opin- 
ion about  securing  it,  either  as  a  new  pavement  or  in  the  replace- 
ment of  an  old  one. 

Popular  prejudices  about  pavements  affect  the  prices  of  real 
estate  upon  paved  streets,  and  so  help  to  determine  their  desir- 
ability. A  stranger's  impression  of  a  city  or  town  depends  largely 
upon  the  ease  with  which  he  can  go  from  place  to  place  in  the 
transaction  of  business  or  in  the  pursuit  of  pleasure,  and  he  is 
pleased  or  displeased  exactly  in  proportion  to  the  smoothness  of 
his  journey  or  the  ruggedness  of  his  way.  Massive  business  blocks, 
pretentious  private  residences,  stately  public  buildings,  beautiful 
parks  and  lawns,  possess  no  attraction  for  one  who  is  compelled  to 
pick  a  way  for  his  feet  and  keep  his  eyes  on  the  ground  for  fear  of 
stumbling  over  jagged  stones  or  falling  in  the  mud.  To  man  and 
beast  alike,  the  roadway  that  offers  a  few  or  no  obstacles  to  easy 
travel  is  a  delight  which  shortens  the  journey  by  mitigating  the 
pangs  of  fatigue. 

To  persons  who  ride  for  pleasure  or  for  health,  rougli  pave- 
ments cause  great  annoyance.  The  pleasure  of  fast  driving  in  the 
parkways  or  roadways  devoted  to  that  purpose  is  defeated  by  the 
necessity  of  jolting  over  rough  pavements  until  the  driveway  is 
reached,  and  in  the  case  of  invalids  the  rough  roadways  prevent 
the  taking  of  air  altogether  in  many  cases. 

11.  The  economic  desirability  of  pavements  is  governed  by  the 
ease  of  movement  over  them,  and  is  measured  by  the  number  of 
horses  or  pounds  of  tractive  force  required  to  move  a  given  weight, 
usually  one  ton,  over  them.     The  following  table  shows  the  relative 


6  HIGHWAY   CONSTRUCTION. 

tractive  force  required  upon  level  roads  formed  of  different  ma- 
terials, asphalt  being  taken  as  the  standard  of  excellence  in  this 
respect : 

TABLE  II. 

NUMBER  OF  HORSES  REQUIRED  TO  MOVE  ONE  TON  ON  DIFFERENT  PAVE. 

MENTS. 

Asphalt *..  1.00 

Stone  blocks,  dry  and  in  good  order 1.50  to  2.00 

infairorder 2.00  "  2.50 

covered  with  mud  2  00  "  2.70 

Macadam,  dry  and  in  good  order 2.50  "  3.00 

in  a  wet  state 3.80 

in  fair  order 4.50 

"          covered  with  mud 5.50 

"          with  the  stones  loose 5.00  "  8.20 

See  also  Tables  L  and  LI,  pages  372  and  375. 

12.  From  Table  II  it  is  seen  that  to  move  the  same  load  at 
the  same  speed  and  for  the  same  length  of  time,  with  the  same 
fatigue  to  each  horse,  requires  from  1|  to  3  horses  on  stone  block 
pavements,  and  2$  to  8£  on  macadam,  while  for  asphalt  but  1  is 
required. 

If  iron  rails  be  taken  .as  the  standard  of  excellence,  the  number 
of  horses  required  will  be  as  follows : 

Iron  rails .  1 

Asphalt li 

Stone  block,  best  condition 3£ 

"        "      ordinary  condition 5 

"      bad  "        8 

Macadam 5.7  to  8 

Cobblestones,  good 6.6  "  13.3 

"          ordinary 25 

Earth,  dry 20 

Sand 40 

13.  Economy  of  Smoothness. — From  the  above  table  the  great 
economy  of  smoothness  becomes  at  once  apparent.    But  it  is  evident 
that,  as  in  all  lines  of  transportation,  the  greatest  resistance  regu- 
lates the  load  over  the  rest  of  the  route,  unless  there  be  auxiliary 
power;  so  the  continuity  of  the  surface  should  remain  unbroken 
by  any  other  grade  of  material  which  would  increase  the  resistance. 


PAVEMENTS. 


The  advantages  of  smooth  pavements  to  owners  and  users  of 
horses  and  vehicles  are  enormous.  With  them  one  third  greater 
loads  could  be  moved ;  there  would  be  no  stuck  teams,  fewer  wor- 
ried, beaten  horses,  fewer  angry,  overworked  drivers,  and  thus  fewer 
delays  and  interruptions  to  business. 

14.  Serviceability. — The   serviceability   of    a  pavement  is  its 
quality  of  fitness  for  use.     This  quality  is  measured  by  the  expense 
caused  to  the  traffic  using  it,  viz.,  the  wear  and  tear  of  horses  and 
vehicles,  loss  of  time,  etc.     No  statistics  are  available  from  which 
to  deduce  the  actual  cost  of  wear  and  tear.     It  has  been  estimated 
.as  follows : 

On  cobblestones 5  cents  per  mile  travelled 

"    belgian  block 4 

"    granite  block 3 

"    wood 2.5 

."    broken  stone  in  first-class  condition...  1.2        " 
"    asphalt 1 

The  serviceability  of  any  pavement  depends  in  a  great  measure 
upon  the  amount  of  foothold  afforded  by  it  to  the  horses,  provided, 
however,  that  its  surface  be  not  so  rough  as  to  absorb  too  large  a 
percentage  of  the  tractive  energy  required  to  move  a  given  load 
over  it.  Cobblestones  afford  excellent  foothold,  and  for  this  reason 
are  largely  employed  by  horse-car  companies  for  paving  between 
the  rails;  but  the  resistance  of  their  surface  to  motion  requires  the 
expenditure  of  about  280  pounds  of  tractive  energy  to  move  a  load 
of  1  ton.  Asphalt  affords  the  least  foothold,  but  the  tractive  force 
required  to  overcome  the  resistance  it  offers  to  motion  is  only  about 
30  pounds  per  ton. 

15.  Comparative  Safety. — The  comparison  of  pavements  in  this 
respect   is  the  distance  travelled  before  a  horse  falls.     The  ma- 
terials affording  the  best  foothold  for  horses  are  as  follows,  stated 
in  the  order  of  their  merit:, 

(1)  Earth  dry  and  compact. 

(2)  Gravel. 

(3)  Broken  stone  (macadam). 

(4)  Wood. 

(5)  Sandstone  and  brick. 

(6)  Asphalt. 

(7)  Granite  blocks. 


HIGHWAY   CONSTRUCTION. 

16.  The  most  complete  observations  made  in  the  United  States 
to  ascertain  the  prevalence  of  accidents  on  the  different  pavements 
were  made  under  the  direction  of  Capt.  F.  V.  Greene,  the  results  of 
which  show  that  a  horse  may  travel  before  falling  on 

Asphalt  (Trinidad) 583  miles 

Granite 413     " 

Wood 272     " 

17.  Observations  for  the  same  purpose  were  made  in  London 
under  the  direction  of  Col.  Haywood.     The  results  were  as  follows. 
The  three  classes  of  pavements,  wood,  asphalt,  and  stone,  were  ob- 
served as  nearly  as  was  possible  under  the  same  conditions  of  space, 
weather,  gradients,  and  soundness.     The  result  of  fifty  days'  ob- 
servation showed  that  before  meeting  with  an  accident  a  horse 
would  travel  a  far  greater  distance  on  wood  than  he  could  either 
on  asphalt  or  stone.     The  following  table  shows  the  distance  trav- 
elled by  a  horse  before  meeting  with  an  accident : 

DRY-WEATHER  DISTANCES. 

Wood 646  miles 

Asphalt 223     " 

Granite 78     " 

DAMP-WEATHER  DISTANCE. 

Wood 193  miles 

Asphalt 125     " 

Granite I«8     " 

THOROUGHLY- WET-WEATHER  DISTANCES. 

Wood 432  miles 

Asphalt 192     " 

Granite 537     " 

Another  mode  of  observation  gave  the  distance  travelled   as 
follows : 

Wood 446  miles 

Asphalt 191     " 

Granite ..  132        „ 

18.  The  foregoing  figures  appear  to  show  that 

(1)  Asphalt  was  most  slippery  when  merely  damp,  and  safest 
when  perfectly  dry. 

(2)  That  granite  was  most  slippery  when  dry  and  safest  when 
wet. 


PAVEMENTS. 


(3)  That  wood  was  most  slippery  when  damp  and  safest  when 
dry.  It  will  be  noticed  that  only  under  a  single  condition,  and 
that  the  least  persistent,  is  granite  safer  than  wood  or  asphalt,  and 
that  wood  is  safer  than  asphalt  under  all  circumstances. 

Granite  was  least  safe  and  wood  and  asphalt  most  safe  when  clean. 

19.  Slight  rain  makes   asphalt  and  wood  more  slippery  than 
they  are  at  other  times.     On  asphalt  the  slipperiness  begins  almost 
immediately  the  rain  commences.     Wood  requires  more  rain  before 
its  worst   condition   ensues.     The  slipperiness  lasts  longer  upon 
wood,  on  account  of  its  absorbent  nature,  than  it  does  upon  the  as- 
phalt.    AVhen  dry  weather  comes  after  the  rain,  then  asphalt  is  in 
its  most  slippery  condition  and  horses  fall  upon  it  very  suddenly. 
On  wood  their  efforts  to  save  themselves  are  more  effectual.     Wood 
is  also  frequently  in  that  peculiar  condition  of  surface  in  which 
horses  slip  or  slide  along  it  without  falling.     A  small  quantity  of 
dirt  on  asphalt  makes  it  very  slippery.     In  damp  weather  granite 
blocks  become  very  greasy  and  slippery;  in  dry  weather,  if  of  a 
hard  variety,  the  surface  polishes  and  becomes  rounded  and  the 
only  foothold  is  by  the  joints  between  the  blocks. 

In  winter,  during  frost,  asphalt  is  usually  dry  and  safe ;  wood, 
retaining  moisture,  is  very  slippery.  Under  snow  there  is  very 
little  if  any  difference  between  the  safety  of  asphalt  and  wood. 

20.  The   difference   in  the   results   obtained  by  Capt.  Greene 
and  Col.  Haywood  may  be  due  in  the  case  of  the  wood  and  stone 
pavements  to  climatic  causes.     London  is  more  damp  and  foggy 
than  any  one  of  the  American  cities  in  which  the  traffic  was  ob- 
served, and  therefore  its  pavements  would  be  more  slippery.     The 
difference  in  the  asphalt  returns  may  be  accounted  for  by  the  dif- 
ference in  the  character  of  the  material.     The  asphalt  pavements  in 
London  are  made  from  natural  bituminous  rock,  which  makes  a  very 
smooth,  hard  surface,  while  the  American  pavements  are  made  from 
natural  bitumen  mixed  with  sand,  which  forms  a  rough,  granular 
surface.     Moreover,  these  observations  were  made  some  eighteen 
^ears  ago,  at  a  time  when  asphalt  was  a  new  thing  and  its  proper 
treatment  very  insufficiently  understood.     It  was  not  then  recog- 
nized that  asphalt  requires  to  be  constantly  and  thoroughly  cleansed 
in  order  to  do  justice  to  itself.     That  the  number  of  falls  on  as- 
phalt is  decreasing  as  its  use  is  becoming  more  extended  is  shown, 
by  the  following : 


10  HIGHWAY   CONSTRUCTION". 

In  Berlin  in  1885,  4403  horses  fell  on  an  area  of  398,000  square 
;yards  of  asphalt  pavement,  in  1887  the  number  was  reduced  to 
2456,  while  the  area  had  increased  to  485,000  square  yards. 

That  asphalt  is  but  slightly  more  dangerous  than  some  kinds 
of  stone  is  shown  by  observations  made  at  Paris  some  years  ago  in 
two  streets,  one  paved  with  the  hard  sandstone  much  used  in  that 
capital,  and  the  other  with  asphalt.  In  the  street  paved  with  stone 
one  out  of  every  1308  horses  fell,  and  in  that  paved  with  asphalt 
one  out  of  every  1409  fell. 

21.  Slipperiness  can  be  cured  on  both  wood  and  asphalt:   on 
the  asphalt  by  sprinkling  it  with  sand,  on  the  wood  by  sprinkling 
it  with  gravel.     The  result  in  both  cases  is  dirt.     The  sand  thrown 
on  the  asphalt  tends  to  wear  it  out ;  the  gravel  thrown  on  the  wood 
tends  to  preserve  it. 

22.  Kinds  of  Falls  and  their  Causes. — The  commonest  falls  on 
wood  are  falls  on  the  knees,  which  are  less  likely  to  injure  the  horses 
and  are  less  inconvenient  to  the  traffic  than  other  falls.     Falls  on 
haunches  are  more  numerous  on  asphalt  than  on  wood.     Of  com- 
plete falls  there  are  fewest  on  wood  and  most  on  granite.     The  falls 
on  asphalt  are  generally  due  to  sudden  pulling  up  and  sharp  turn- 
ing; those  on  granite,  to  the  excessive  width  of  the  blocks,  which 
fail  to  afford  proper  foothold. 

23.  Durability. — The  durability  of  a  pavement  is  its  quality, 
ivhich  relates  to  the  length  of  time  during  which  it  is  serviceable 
^and  not  to  the  length  of  time  it  has  been  down.     The  only  meas- 
ure of  the  durability  of  a  pavement  is  the  amount  of  traffic  tonnage 
it  will  bear  before  it  becomes  so  ivorn  that  the  cost  of  replacing  it 
is  less  than  the  expense  incurred  by  its  use. 

24.  As  a  pavement  is  a  construction,  it  necessarily  follows  that 
there  is  a  vast  difference  between  the  durability  of  the  pavement 
-and  the  durability  of  the  materials  of  which  it  is  made.     Iron  is 
•eminently  durable,  but  as  a  paving  material  it  is  a  failure. 

25.  Durability  and  Dirt. — The  durability  of  a  paving  material 
will  vary  considerably  with  the  condition  of  cleanliness  observed. 
One  inch  of  overlying  dirt  will  most  effectually  protect  the  pave- 
ment from  abrasion  and  indefinitely  prolong  its  life.     But  the  dirt 
is  expensive,  it  injures  apparel  and  merchandise,  and  is  the  cause 
of  sickness  and  discomfort.     In  the  comparison  of  different  pave- 
ments no  traffic  should  be  credited  to  the  dirty  one. 


PAVEMENTS. 


26.  A  pavement  so  rough  and  insecure  that  the  traffic  is  kept 
off  the  road  might  be  a  most  durable  one,  but  it  certainly  would 
be   lacking   in  serviceability.     In  a  general  way  of  speaking,  the 
value  of  city  property  depends  upon  the  volume  of  the  traffic  in 
the  street  upon  which  it  is  located.     Ordinarily  a  pavement  is  not 
wanted  by  the  owners  of  property  on  the  street,  however  durable  it 
may  be,  if  it  lacks  serviceability;  and  they  may  not  want  it,  even 
when  it  is  serviceable,  if  it  is  not  popular. 

27.  Life  of  Pavements. — The  life  or  durability  of  the  different 
pavements  under  like  conditions  of  traffic  and  maintenance  may  be 
taken  as  follows : 

Granite  block 12  to  30  years 

Sandstone 6  "  12 

Asphalt  10"  14 

Wood 3"    7 

Limestone 1  "    3 

Brick 5"     ? 

Macadam ? 

28.  Cost. — The  question  of  cost  is  the  one  which  usually  inter- 
ests the  taxpayers,  and  is  probably  the  greatest  stumbling-block  in 
the  attainment  of  good  roadways.     The  first  cost  is  usually  charged 
against  the  property  abutting  on  the  highway  to  be  improved.     The 
result  is  that  the  average  property-owner  is  always  anxious  for  a 
pavement  that  costs  little,  because  he  must  pay  for  it,  not  caring 
for  the  fact  that  cheap  pavements  soon  wear  out  and  become  a 
source  of  endless  annoyance  and  expense.     Thus  false  ideas  of  econ- 
omy always  have  stood  and  undoubtedly  to  some  extent  always  will 
stand  in  the  way  of  realizing  that  the  best  is  the  cheapest. 

29.  The  pavement  which  has  cost  the  most  is  not  always  the 
best,  nor  is  that  which  has  cost  the  least  the  cheapest ;  the  one  which 
is  truly  the  cheapest  is  the  one  which  makes  the  most  profitable  re- 
turns in  proportion  to  the  amount  which  has  been  expended  upon  it. 
No  doubt  there  is  a  limit  of  cost  to  go  beyond  which  would  produce 
no  practical  benefit,  but  it  will  always  be  found  more  economical 
to  spend  enough  to  secure  the  best  results,  and  it  will  always  cost 
less  in  the  long-run.     One  dollar  well  spent  is  many  times  more 
effective  than  one  half  the  amount  injudiciously  expended  in  the 
hopeless  effort  to  reach  sufficiently  good  results  which  may  look  as 


12  HIGHWAY   CONSTRUCTION. 

well  for  the  time,  no  matter  how  soon  it  may  have  to  be  done  over 
again. 

30.  A  good  roadway  should   cost  more  to  build  than  a  poor 
one,  but  it  is  often  the  case  that  the  poor  road  costs  as  much  as  a- 
good  one  would.     But  even  when  a  good  one  is  more  expensive,  it 
will  be  easier  and  cheaper  to  keep  in  repair,  and  will  last  many 
years  longer,  while  its  advantages  and   the  saving  to  those  wha 
daily  use  it  will  much  more  than  compensate  for  the  extra  expense 
they  may  have  been  put  to  in  building  it. 

31.  Economy  and  Public  Bodies. — The  true  economy  for  public 
bodies  which  never  die  is  to  secure  the  best,  in  the  best  possible 
manner;  for  the  best,  every  essential  point  being  considered,  is  the 
cheapest.     If  a  cheap  pavement  is  adopted,  the  cost  to  maintain  it 
will  be  so  excessive  as  to  more  than  make  the  difference  between 
its  first  cost  and  that  of  a  first-class  one.    As  an  instance  of  the 
profitable  results  of  this  policy  the  experience  of  the  city  of  Liver- 
pool, England,  may  be  cited. 

After  many  years  of  experiment  and  the  expenditure  of  vast 
sums  of  money  in  pavements,  ihe  corporation  of  Liverpool  now 
points  with  justifiable  pride  to  its  250  miles  of  the  best  paved 
streets  in  the  world. 

The  policy  adopted  by  this  corporation  in  the  execution  of 
public  works  in  the  best  possible  manner,  and  generally  by  their 
own  workmen,  has  proved  successful  in  every  way  ;  and,  by  a 
judicious  primary  expenditure,  the  cost  of  maintenance  of  the  roads, 
sewers,  and  other  public  works  is  reduced  to  a  minimum,  and  the 
greatest  economy  is  thereby  attained. 

The  laying  of  the  impervious  pavement  which  was  adopted  in 
1872  for  the  carriage-ways  of  the  city  has  been  continued  up  to 
date  without  intermission,  and  is  still  in  progress,  resulting  in 
nearly  1,750,000  yards,  superficial,  of  impervious  carriage-way  pave- 
ments, and  a  saving  by  the  execution  of  this  class  of  work  unpre- 
cedented in  municipal  experience. 

The  financial  result  can  best  be  shown  by  the  following:  "  Deal- 
ing with  the  year  1879,  under  the  present  city  engineer  (Mr.  Clem- 
ent  Dunscombe,  M.A.,  M.  Inst.  C.  E.),  the  estimated  expenditure  for 
the  general  repairs  to  the  roads  in  this  city  was  £28,000  ($136,080), 
the  mileage  of  adopted  roads  at  that  time  being  226  miles. 
Concurrently  with  the  extension  of  the  impervious  carriage-way 


PAVEMENTS.  13 


pavements,  the  expenditure  under  this  head  has  been  reduced  year 
by  year  till  the  estimated  cost  for  the  current  year  (1889)  is  only 
£8400  ($40,824),  with  a  street  mileage  under  repair  of  254  miles. 
This  reduction  has  not  been  effected,  as  might  at  first  sight  be 
supposed,  by  an  increased  rate  under  this  head,  due  to  an  aug- 
mented expenditure  of  capital  requiring  the  provision  of  additional 
interest  and  sinking  fund  to  redeem  the  original  debt  for  paving 
and  like  works  within  23  years  (from  1870,  when  the  loan  was 
effected,  to  1893,  when  it  will  be  paid),  as  the  amount  raised  on 
paving-rate  account  in  the  year  1879  was,  approximately,  £17,000 
($82,620)  more  than  in  the  year  1889,  although  the  interest  and 
sinking  fund  on  the  debt  had  increased  from  about  £13,000 
($63,180)  per  annum  in  the  year  1879  to  about  £47,000  ($228,420) 
per  annum  in  the  year  1889." 

Permission  is  never  given  to  private  companies  or  persons  to  cut 
through  the  pavement  in  any  street  for  any  purpose.  When  such 
work  is  necessary,  the  corporation  will  do  it  in  its  own  thorough 
way,  and  the  interested  parties  must  pay  the  entire  cost — a  regula- 
tion worth  noting. 

With  the  introduction  of  the  improved  pavements,  it  was  found 
absolutely  necessary,  in  order  to  attain  the  best  results,  to  purchase 
the  street-railroad  tracks  and  reconstruct  them  in  connection  with 
the  new  pavements.  Accordingly  the  city  purchased  some  fifty 
miles  of  street-railroad  tracks,  and  reconstructed  them  in  a  most 
substantial  manner,  and  then  rented  them  to  the  several  original 
car  companies  at  a  fixed  annual  rental  of  10  per  cent  on  their  cost. 
The  city  keeps  the  tracks  in  good  condition.  The  success  of  these 
lines  is  conclusive  proof  that  when  street-car  tracks  are  well  de- 
signed and  properly  constructed  they  do  not  form  the  slightest 
impediment  even  to  the  narrowest-wheeled  vehicles. 

32.  Economic  Benefit. — The  economic  benefit  of  a  good  road- 
way is  comprised  in  its  cheaper  maintenance,  greater  and  easier 
facility  for  travelling,  thus  reducing  the  cost  of  transportation,  less 
cost  of  repairs  to  vehicles,  less  wear  of  horses  (thus  increasing  the 
life  and  time  of  serviceability  and  enhancing  the  value  of  their 
present  service),  saving  of  time,  ease  and  comfort  to  those  using  it. 

33.  First  Cost.— The  cost  of  construction  is  largely  controlled 
by  the  locality  of  the  place,  its  proximity  to  the  particular  material 
used,  and  the  character  of  the  foundation.   Tables  XXVII,  XXVIII, 


14  HIGHWAY   CONSTRUCTION. 

XXIX,  XXX,  XXXV,  XXXVI,  XXXVII,  XLI,  XLII,  and  XLIII 
show  the  cost  of  different  pavements  in  several  of  the  principal 
cities  of  America. 

34.  The   Relative   Economies  of    Pavements — whether  of  the 
same  kind  in  different  condition  or  different  kinds  in  like  good 
condition — are  sufficiently  determined  by  summing  their  cost  under 
the  following  headings  of  account : 

(1)  Annual  interest  upon  first  cost. 

(2)  Annual  expense  for  maintenance. 

(3)  Annual  cost  for  cleaning  and  sprinkling. 

(4)  Annual  cost  for  service  and  use. 

(5)  Annual  cost  for  consequential  damages. 

35.  First. — The  first  cost  of  a  pavement  is  like  any  other  per- 
manent investment,  measurable  for  purposes  of  comparison  by  the 
amount  of  annual  interest  on  the  sum  expended.     Thus,  assuming 
the  worth  of  money  to  be  4$,  a  pavement  costing  $4  per  square 
yard  entails  an  annual  interest  loss  or  tax  of  $0.16  'per  square  yard. 

36.  Second.  Maintenance. — Under  this  head  must  be  included 
all  outlays  for  repairs  and  renewals  which  are  made  from  the  time 
when  the  pavement  is  new  and.  at  its  best  to  a  time  subsequent 
when,  by  any  treatment,  it  is  again  put  in  equally  good  condition. 
The  gross  sum  so  derived  divided  by  the  number  of  years  which 
elapse  between  the  two  dates  gives  an  average  annual  cost  for 
maintenance. 

37.  Maintenance  means  the  keeping  of  the  pavement  in  a  con- 
dition practically  as  good  as  when  first  laid.     The  cost  will  vary 
considerably,  depending  not  only  upon  the  material  and  manner  in 
which  it  is  constructed,  but   upon   the   condition   of   cleanliness 
observed,  and  the  quantity  and  quality  of  the  traffic  using  it. 

38.  The  prevailing  opinion  that  no  pavement  is  a  good  one 
unless  when  once  laid  it  will  take  care  of  itself  is  erroneous;  there 
is  no  such  pavement.     All  pavements  are  being  constantly  worn  by 
traffic  and  the  action  of  the  atmosphere,  and  if  any  defects  which 
appear  are  not  quickly  repaired  they  soon  become  unsatisfactory 
and  are  destroyed.     To  keep  them  in  good  repair  incessant  atten- 
tion is  necessary  and  is  consistent  with  economy.     Yet  claims  are 
made  that  particular  pavements  cost  little  or  nothing  for  repairs, 
simply  because  repairs  are  not  made,  while  any  one  can  see  the 
need  of  them. 

39.  Third. — Any  pavement,  to  be  considered  as  properly  cared 


PAVEMENTS.  15 


for,  must  be  kept  dustless  and  clean.  While  circumstances  legiti- 
mately determine  in  many  cases  that  streets  must  be  cleaned  at 
daily,  weekly,  or  semi-weekly  intervals,  the  only  admissible  condi- 
tion for  the  purpose  of  analysis  of  street  expenses  must  be  that  of 
like  requirements  in  both  or  all  cases  subjected  to  comparison. 

40.  The  cleansing  of  pavements  both  as  regards  its  efficiency 
and  cost  depends  (1)  upon  the  character  of  the  surface;  (2)  upon 
the  nature  of  the   material  of  which  they  are  composed.     Block 
pavements  present  the  greatest  difficulty;  the  joints  can  never  be- 
perfectly  cleansed.     The  order  of  merit  for  facility  of  cleansing  is 
(1)  asphalt,  (2)  brick,  (3)  stone,  (4)  wood,  (5)  macadam. 

41.  Fourth. — The  annual  cost  for  service  is  made  up  by  com- 
bining several  items  of  cost  incidental  to  the  use  of  the  pavement 
for  traffic;  for  instance,  the  limitation  of  the  speed  of  movement,, 
as  in  cases  where  a  bad  pavement  causes  slow  driving   and  the 
consequent  loss  of  time;  or  cases  where  the  condition  of  a  pave- 
ment limits  the  weight  of  the  load  which  the  horse  can  haul,  and 
so  compels  the  making  of  more  trips  or  the  employment  of  more 
horses  and  vehicles;  or  cases  where  it  causes  greater  wear  and  tear 
of  vehicles,  of  equipage,  and  of  horses.     If  a  vehicle  is  run  1500 
miles  in  a  year  and  its  maintenance  costs  $30  a  year,  then  the  cost 
of  its  maintenance  per  mile  travelled  is  two  cents.     If  the  value  of 
a  team's  time  is,  say,  $1  for  the  legitimate  time  taken  in  going  one- 
mile  with  a  load,  and  in  consequence  of  bad  roads  it  takes  double- 
that  time,  then  the  cost  to  traffic  from  having  to  use  that  one  mile 
of  bad  roadway  is  $1  for  each  load.     The  same  reasoning  applies  ta 
circumstances  where  the  weight  of  the  load  has  to  be  reduced  so  as- 
to  necessitate  the  making  of  more  than  one  trip.     Again,  bad  pave- 
ments lessen  not  only  the  life-service  of  horses,  but  also  the  value 
of  their  current  service.     The  unit  of  these  accounts  is  obtained  by 
first  finding  the  cost  per  mile  of  distance  travelled,  which  cost, 
divided  by  5.280  and  multiplied  by  the  unit  of  area  gives  the 
desired  result. 

42.  Fifth.  Consequential  Damages.— The  determination  of  con- 
sequential damages  arising  from  the  use  of  defective  or  unsuitable 
pavements  involves  the  consideration  of  a  wide  array  of  diverse 
circumstances.      Eough-surfaced   pavements,  when   in   their  best 
condition,  afford  a  lodgment  for  organic  matter  composed  largely 
of  the  urine  and  excrement  of  the  animals  employed  upon  the  road- 


16  HIGHWAY    CONSTRUCTION. 

way.  In  warm  and  damp  weather  these  matters  undergo  putre- 
factive fermentation  and  become  the  most  efficient  agency  for 
generating  and  disseminating  noxious  vapors  and  disease-germs, 
now  recognized  as  the  cause  of  a  large  part  of  the  ills  afflicting  man- 
kind. Pavements  formed  of  porous  materials  are  objectionable  on 
the  same  if  not  even  stronger  grounds. 

43.  Pavements  productive  of  dust  and  mud  are  objectionable,, 
and  especially  so  on  streets  devoted  to  retail  trade.  If  this  particu- 
lar disadvantage  be  appraised  at  so  small  a  sum  per  lineal  foot  of 
frontage  as  $1.50  per  month,  or  six  cents  per  day,  it  exceeds  the  cost 
of  the  best  quality  of  pavement  free  from  these  disadvantages. 
Rough-surfaced  pavements  are  noisy  under  traffic  and  insufferable 
to  nervous  invalids,  and  much  nervous  sickness  is  attributable  to 
them.  To  all  persons  interested  in  nervous  invalids  this  damage 
from  noisy  pavements  is  rated  as  being  far  greater  than  would  be 
the  cost  of  substituting  the  best  quality  of  noiseless  pavement;  but 
there  are,  under  many  circumstances,  specific  financial  losses,  meas- 
urable in  dollars  and  cents,  dependent  upon  the  use  of  rough,  noisy 
pavements.  They  reduce  the  rental  value  of  buildings  and  offices 
situated  upon  streets  so  paved,  offices  devoted  to  pursuits  wherein 
exhausting  brain-work  is  required.  In  such  locations  quietness  is 
almost  indispensable,  and  no  question  about  the  cost  of  a  noiseless 
pavement  weighs  against  its  possession.  When  an  investigator  has 
done  the  best  he  can  to  determine  such  a  summary  of  costs  of  a 
pavement,  he  may  divide  the  amount  of  annual  tonnage  of  the  street 
traffic  by  the  amount  of  annual  costs  and  know  what  number  of 
tons  of  traffic  are  borne  for  each  cent  of  the  average  annual  cost, 
which  is  the  crucial  test  for  any  comparison,  as  follows : 


(1)  Annual  interest  upon  the  first  cost 

(2)  Average  annual  expense  for  maintenance  and  renewal. 
(8)  Annual  cost  for  custody  (sprinkling  and  cleaning). . . . 

(4)  Annual  cost  of  service  and  use  . .    

(5)  Annual  cost  of  consequential  damages.   

Amount  of  average  annual  cost 

Annual  tonnage  of  traffic 

Tons  of  traffic  for  each  cent  of  cost. . 


44.  Gross  Cost  of  Pavements. — Since  the  cost  of  a  pavement 
depends  upon  the  material  of  which  it  is  formed,  the  width  of  the 
roadwav,  the  extent  and  nature  of  the  traffic,  the  condition  of 


PAVEMENTS.  17 


repair  and  cleanliness  in  which  it  is  maintained,  it  follows  that  in 
no  two  streets  is  the  endurance  or  the  cost  the  same,  and  the  differ- 
ence between  the  highest  and  lowest  periods  of  endurance  and 
amount  of  cost  is  very  considerable. 

The  comparative  cost  of  various  street  pavements  in  Liverpool, 
including  interest  on  first  cost,  sinking  fund,  maintenance,  and 
cleaning,  when  reduced  to  a  uniform  standard  traffic  of  100,000 
tons  per  annum  for  each  yard  in  width  of  the  carriage-way,  is  given 
by  Mr.  Deacon  as  follows : 

Per  Square  Yard  per  Annum. 

Block  pavements  of  hard  granites $0. 23 

"softer      "      0.28 

Bituminous  concrete 0.85 

Wood  pavement 0.53 

Macadam,  on  pitch  foundation 0.71 

Taking  the  standard  of  traffic  at  40,000  tons  per  annum,  for  each 
yard  in  width  the  cost  for  the  last  three  pavements  is : 

Bituminous  concrete , 0.27 

Wood 0.41 

Macadam 0.47 

Asphalt  may  be  placed  between  wood  and  bituminous  concrete, 
in  the  above  order.  These  comparisons  show  the  high  cost  of  a 
macadamized  surface  in  a  street  where  traffic  is  great ;  and  however 
well  it  may  be  maintained,  it  is  much  dirtier  and  dustier  than  any 
other  pavement,  though  it  is  superior  to  them  all  in  safety,  and  to 
block  pavements  in  the  matter  of  noise. 

Table  III  shows  the  approximate  comparative  gross  cost  of 
various  pavements  in  the  United  States  for  a  period  of  fifty  years, 
the  pavement  at  the  end  of  that  period  to  be  in  as  good  condition 
as  when  first  laid. 

45.  Traffic  Census. — Comparison  of  pavements  in  respect  to 
their  gross  cost  can  be  effected  only  by  comparing  the  gross  traffic 
tonnage  which  each  will  bear  for  a  unit  of  cost.  As  this  can  be 
ascertained  only  by  direct  observation,  it  is  desirable  that  engineers 
in  charge  of  roads  and  streets  find  out  accurately  the  traffic  tonnage, 
the  amount  of  force  required  to  draw  a  unit  of  weight  over  differ- 
ent surfaces  in  like  condition,  the  cost  of  maintaining  different 
•coverings  during  a  given  period  under  a  unit  of  traffic  tonnage,  the 


18 


HIGHWAY   CONSTRUCTION. 


TABLE   III. 
COMPARISON  OF  THE  GROSS  COST  OF  PAVEMENTS  FOR  A  PERIOD  OF  50  YEARS. 


Granite 
Block. 

Asphalt. 

Wood. 

Brick. 

Foundation    6  in  concrete       .    

$1    00 

$1.00 

$1.00 

$1.00 

,3.25 

2.50 

1.40 

1.80 

Total  first  cost      

4  25 

3.50 

2  40 

2.80 

Interest  on  materials  aud  sinking  fund, 
50  yrs  @  4  %                            

26  00 

20  00 

11  20 

14  40 

Interest  on  foundation  @  4  $  

2  00 

2.00 

2  00 

2  00 

2.50 

4.50 

7.50 

2.50 

Cleauin0"  etc    50  years                     .  . 

5  00 

1  00 

6  00 

2  50* 

3  renewals  of  surface  @  $3  25  

9  75 

5                                     @    2.50  

12.50 

12        "                 "        @    1  40 

16  80 

8        "                 "        @    1  80  

14  40 

Cost  of  service  (estimated  at) 

30  00 

10  00 

20  00 

15  00 

"    "  consequential  damages  (  "        ") 
Total  

10.00 
89  50 

1.00 
54  50 

1.50 
67  40 

2.00 
55  60 

1  00 

1  00 

1  00 

1  00 

Less  value  of  old  material.  .  . 

88.50 
1  00 

58.50 
10 

66.40 

54.60 
25 

+  50) 

Annual  gross  cost  

87.50 
1  75 

53.40 
1  068 

66.40 
1  33 

54.35 

1  087 

Cost  per  Square  Yard. 


relative  safety  of  different  surfaces,  and  the  damage  done  to  vehicles 
and  horses  by  different  pavements.  These  items  should  be  care- 
fully observed  and  recorded.  As  the  amount  of  travel  is  variable, 
the  observations  should  be  made  for  a  certain  period  on  con- 
secutive days,  and  should  be  repeated  at  different  seasons  of  the 
year. 

46.  The  most  extensive  observations  on  this  subject  in  the 
United  States  were  made  under  the  direction  of  Capt.  F.  V.  Greene, 
member  of  the  American  Society  of  Civil  Engineers.  The  method 
of  observing  and  recording  was  as  follows :  "  The  observations  were 
made  on  six  consecutive  days  (Sundays  omitted)  at  the  same  place, 
and  were  continuous  from  7  A.M.  to  7  P.M.,  except  when  darkness 
prevented.  No  addition  was  made  for  this  omission,  nor  for  night 
traffic." 


PAVEMENTS.  19 


The  printed  instructions  issued  to  each  observer  contained  the 
following  rules  as  a  guide  in  estimating  weights : 

Less  than  1  ton. 

1-horse  carriages,  empty  or  loaded. 
1-horse  wagons,  empty  or  light  loaded. 
1-horse  carts,  empty. 

Between  1  and  3  tons. 
1-horse  wagons,  heavy  loaded. 
1-horse  carts,  loaded. 
2-horse  wagons,  empty  or  light  loaded. 

Over  3  tons. 
Wagons  and  trucks  drawn  by  two  or  more  horses  and  heavy  loadel. 

"  Special  note  will  be  made,  in  the  column  of  Eemarks,  of  any 
unusually  heavy  loads,  such  as  6-horse  trucks  loaded  with  stone  or 
iron,  and  an  estimate  given  of  their  weight." 

The  weight  and  number  of  the  horses  was  disregarded,  because 
Capt.  Greene  wished  to  make  comparison  with  English  reports  in 
which  their  weight  was  disregarded.  Their  weight  should  be  in- 
cluded in  all  observations,  as  the  action  of  their  feet  is  an  impor- 
tant factor  in  the  ivear  of  pavements. 

47.  Capt.  Greene  assigned  the  following  weights  to  each  class 
of  vehicles : 

Light-weight  vehicles  one- half  ton  each,  including  their  load; 
medium  weight  two  tons,  and  the  heavy  weight  four  tons. 

The  weight  to  be  assigned  to  each  class  of  vehicles  had  better 
be  ascertained  by  occasionally  weighing  a  typical  vehicle  and  its 
load.  The  weight  of  horses  may  be  taken  at  one-half  ton  each. 

48.  Form  of  Traffic  Census. 

TRAFFIC  CENSUS 

of Street. 

Class  of  parement 

Condition 

Width  between  curbs 

Date  of  observation 

State  of  the  weather 

Temperature 

Name  of  observer < 


HIGHWAY   CONSTRUCTION. 


Classification 
of  Vehicles. 

Hours  of  Observation. 

6  to  7. 

7  to  8. 

8  to  9. 

9  to  10. 

10  to  11. 

11  to  12. 

12tol. 

1-           loaded 

2_           light  

2-           loaded 

3.           light  

3-           loaded  

4-           liehl.  . 

4-           loaded  ,.. 

Led  horses,  No.  of.  ... 
Totals     

Number  of  falls 

Remarks    ... 

49.  To  obtain  tonnage,  multiply  the  total  number  of  vehicles 
in  each  class  by  the  weights  assigned  to  that  class,  and  adding  to- 
gether the  products  the  total  vehicular  tonnage  is  ascertained, 
which  divided  by  the  width  between  curbs  and  the  number  of  days 
of  observation  gives  the  average  daily  tonnage  per  foot  of  width. 

Under  Condition  note  the  state  of  repair  and  cleanliness; 
whether  the  surface  is  dry,  damp,  or  greasy.  Under  Falls  note  the 
kind,  whether  on  knees,  haunches,  or  complete,  and  if  possible  the 
cause. 

"  The  average  tonnage  per  vehicle  is  an  almost  infallible  indi- 
cator of  the  character  of  the  street,  i.e.,  whether  devoted  to  resi- 
dential or  business  purposes:  It  ranges  from  0»68  tons  on  Fifth 
Avenue,  New  York  City,  to  2.08  tons  on  a  portion  of  Wabash  Ave- 
nue, Chicago.  The  same  character  is  indicated  by  the  proportions 
of  light  and  heavy  vehicles  in  the  street.  On  Fifth  Avenue,  New 
York,  for  instance,  91$  of  all  the  vehicles  weigh  less  than  one  ton, 
while  on  Wabash  Avenue  only  25$  of  them  have  so  little  weight. 
The  general  average  for  all  cities  is  as  follows:  Less  than  1  ton,  67$; 
between  1  and  3,  26$;  more  than  3  tons,  7$.  The  average  tonnage 
per  foot  of  width  in  each  city,  so  far  ai  here  observed,  varies  from 
151  in  New  York  to  30  in  Buffalo,  and  the  general  average  is  77. 
For  all  the  cities  observed  the  average  daily  tonnage  per  foot  of 
width  is  77,  and  varies  from  273  tons  on  Broadway,  New  York,  to 
7  tons  on  a  granite  street  in  St.  Louis.  The  average  weight  per 
vehicle  is,  for  all  cities,  1.15  tons.  The  average  width  of  the 
streets  between  curbs  is  44  feet." 

In  London  the  traffic  on  some  of  the  asphalt-  and  wood-paved 
streets  exceeds  400  tons  per  foot  of  width  per  day. 


PAVEMENTS. 


21 


In  Liverpool  granite-block  pavements  sustain  a  daily  traffic 
tonnage  per  foot  of  width  of  from  400  to  500  tons. 

The  comparative  rank  of  pavements  in  the  order  of  their  merit 
is  shown  in  Table  IV. 

TABLE  IV. 

COMPARATIVE  RANK  OF   PAVEMENTS,   NAMED  IN  THE  ORDER  OP   THEIR 

MERIT. 


Order 
of 
Merit. 

Durability. 

Service- 
ability. 

Hygienic 
Fitness. 

Service 
on 
Grades. 

Gross 
Annual 
Cost. 

Facility 
for 
Cleansing. 

1 
2 

Granite 
Asphalt 

Asphalt 
Brick 

Asphalt 
Brick 

Granite 
Brick 

Asphalt 
Brick 

Asphalt 
Brick 

3 

Brick 

Wood 

Granite 

Wood 

Wood 

Granite 

4 

Wood 

Granite 

Wood 

Asphalt 

Granite 

Wood 

50.  Guaranteeing  Pavements. — To  secure  pavements  that  shall 
be  durable  and  serviceable,  the  municipal  authorities  often  require 
the  contractors  to  guarantee  their  pavements  for  a  term,  usually,  of 
five  years,  under  provisions  calling  for  maintenance  in  good  condi- 
tion during  that  period  of  time  and  for  final  delivery  in  good  or- 
der.    Such  contracts  involve  two  kinds  of  service,  that  of  construc- 
tion, and  of  maintenance  for  a  limited  period.     In  the  latter  the 
conditions  are  exacted  indiscriminately  alike  on  streets  with  heavy 
traffic  and  on  those  with  very  light  traffic,  and  thereby  become 
sometimes  burdensome,  unless  the  same  contractor  paves  so  many 
streets  of  all  kinds  as  to  correct  the  inequality  by  securing  of  fair 
average  traffic  condition.     The  correct  policy  to  pursue  in  contract- 
ing for  maintenance  would  be  to  measure  the  service  of  the  pave- 
ment by  the  tonnage  rather  than  by  the  years.     To  do  so  equitably 
the  city  needs  information  about  the  traffic,  which  it  can  obtain 
only  by  having  a  traffic  census  taken  as  described  in  Art.  45. 

51.  Many  contracts  for  street  pavements   in  some   European 
cities  have  provided  for  the  construction  and  the  maintenance  of 
the  pavements  for  long  terms,  say  of  twenty  years,  payments  to 
be  made  in  equal  annual  instalments  throughout  the  term.     Such 
arrangements  appeared  at  first  to  be  very  favorable,  owing  to  the 
first  payments  being  so  much  less  than  they  otherwise  would  be 
for  the  whole  cost  of  construction.     The  pro-rata  annual  payments 


HIGHWAY   CONSTRUCTION. 


provided  for  the  interest  and  risks  of  various  kinds,  with  contrac- 
tors' profits  thereon,  in  addition  to  the  direct  outlays  for  construc- 
tion and  repairs,  so  that  the  final  outcome  was  unsatisfactory  to 
both  parties  to  the  contract.  The  prevailing  custom  in  this  coun- 
try is  to  pay  the  cost  of  construction  of  a  pavement  as  soon  as  com- 
pleted. Two  methods  of  meeting  the  expense  of  maintenance  are 
followed.  In  one  the  municipality  meets  the  annual  requirements 
as  they  occur,  and  in  the  other,  under  contract  for  a  term,  say,  of 
ten  or  twenty  years,  the  contractor,  for  equal  annual  payments,  is 
required  to  keep  the  pavement  and  turn  it  over  to  his  successor  in 
good  condition  at  the  expiration  of  the  contract. 

In  the  city  of  New  York  the  guarantee  period  for  asphalt  pave- 
ments is  fifteen  years,  during  which  payments  are  made  as  follows: 
on  completion  of  the  work  seventy  per  cent  of  the  cost;  ac  the  ex- 
piration of  five  years  three  per  cent  is  paid  yearly  for  the  period  of 
ten  years. 

52.  This  annual  payment  has  to  cover  the  contingency  of  the 
contractor's  being  at  the  expense  of  completely  renewing  the  pave- 
ment.    The  equal  annual  amounts  paid  on  contracts  for  mainte- 
nance, as  just  explained,  include  two  funds,  one  of  repair  accounts 
and  the  other  a  sinking  fund,  intended  to  meet  the  cost  of  renew- 
ing the  pavement,  which  must  be  done  if  the  contract  is  for  a  long 
term  of  years. 

53.  If  an  attempt  is  made  to  separate,  for  each  year,  the  pro- 
portion of  the  annual  payment  which  should  provide  for  each  of 
the  two  purposes,  it  would  be  found  that  the  earlier  years  would  be 
contributing  little  or  nothing  for  repairs,  as,  the  pavement  being 
new,  they  would  not  be  required,  but  the   proportion  so  applied 
would  increase  gradually,  and  at  last  consume  nearly  all  the  annual 
payment. 

54.  The  justification  of  contracts  for  the  continuous  mainte- 
nance of  pavements  is  in  the  advantage  gained  from  having  some 
one  admittedly  responsible  for  their  condition  and  more  amenable 
to  discipline  than  are  city  officials  for  neglect.     With  this  consid- 
eration in  mind  each  community  can  determine  whether  it  is  to  its 
advantage  or  not  to  contract  for  such  maintenance. 

55.  Destruction  of  Pavements. — The  most  serious  cause  of  the 
destruction  of  street  pavements  is  the  frequency  with  which  they 
are  torn  up  for  the  introduction  and  repairing  of  underground 
pipes,  and  no  pavement  can  be  designed  which  will  withstand  such 
frequent  disturbance.     The  only  radical  remedy  for  this  evil  is  a 


PAVEMENTS.  23 


Tery  costly  one  in  its  first  inauguration,  but  it  is  one  that  would  be 
•economical  in  the  end,  and  that  is  a  subway  or  series  of  subways 
under  our  roadways. 

56.  The  amount  of  money  wasted  in  continually  opening  up 
the  streets,  digging,  bracing,  and  refilling,  is  a  considerable  item, 
not  counting  the  interference  with  travel  and  business,  and  would 
be  sufficient  to  cover  the  interest  on  the  cost  of  the  subways.     The 
waste,  being  distributed  through  many  companies,  is  not  sufficiently 
felt  to  cause   a  reconstruction.     The  streets  of  New  York  were 
opened  27,088  times  in  1890  by  the  gas,  steam-supply,  and  other 
companies,  and  during  189-4  17,475  openings  were  made,  in  con- 
nection with  which  there  were  relaid  27,500  square  yards  of  asphalt 
pavement,  and  166,000  square  yards  of  granite  pavement. 

In  Washington,  D.  C.,  during  1893,  the  total  surface  of  pave- 
ment removed  and  restored  in  connection  with  openings  in  the 
streets  was  19,652  square  yards,  at  a  cost  of  $47,594.83. 

57.  Under  the  best  municipal  administrations  of  Europe  neither 
-corporations   nor   individuals  are  permitted  to  disturb  the  pave- 
ments.    All  removals  and  restorations  are  done  by  the  city's  own 
employes,  upon  the  deposit,  by  the  parties  who  require  the  streets 
to  be  opened,  of  a  sufficient  sum  to  cover  the  expense  for  each 
piece  of  paving  done,  at  a  fixed  price  per  yard  according  to  the 
kind  of  pavement. 

Moreover,  interference  with  the  pavements  is  of  rare  occur- 
rence, for  the  companies  having  pipes  underground  are  required  to 
thoroughly  examine  and  reinstate  their  mains  and  services  concur- 
rently with  the  paving  of  a  street,  of  the  execution  of  which  due 
notice  is  given  them  by  the  city.  Such  regulations  are  quite  prac- 
tical, and  there  can  be  no  hardship  in  requiring  American  compa- 
nies to  pay  for  like  work. 

In  New  York  the  Department  of  Public  "Works  has  an  organ- 
ized system  of  supervision  to  insure  the  proper  restoration  of  the 
pavements  torn  up  by  private  corporations.  The  companies  or  in- 
dividuals making  the  openings  are  required  to  pay  the  cost  of  in- 
spection as  well  as  the  cost  of  restoring  the  pavement. 

It  is  stated  that  in  Victoria  Street,  one  of  London's  busiest 
thoroughfares,  not  a  single  stone  has  been  disturbed  from  the  car- 
riage-way in  twenty-five  years.  This  street,  as  well  as  many  others, 
has  a  subway  in  which  are  contained  the  gas  and  water  pipes  and 
upwards  of  six  conduits  for  telegraph  and  electric 


UN1V       J-iTY 


CHAPTER  II. 

MATERIALS    EMPLOYED    IN    THE    CONSTRUCTION    OF 
PAVEMENTS. 

58.  Selection  of  Paving  Material. — The  materials  most  com- 
monly used  for  pavements  are  stone  in  the  form  of  blocks  and 
broken  fragments:   wood  in   the  form   of  blocks   and  plank,  as- 
phalt in  two  forms, — sheet  and  block, — and  clay  in  the  form  of 
brick. 

59.  In  considering  the  relative  fitness  of  the  various  materials, 
the  following  physical  and  chemical  qualities  must  be  sought  for: 

(1)  Hardness,  or  that  disposition  of  a  solid  which  renders  it 
difficult  to  displace  its  parts  among  themselves. 

(2)  Toughness,  or  that  quality  by  which  it  will  endure  light  but 
rapid  blows  without  breaking. 

(3)  Ability  to  withstand  the  destructive  action  of  the  weather, 
and  probably  some  organic  acids  produced  by  the  decomposition  of 
excretal  matters,  always  present  upon  roadways  in  use. 

(4)  The  porosity,  or  water-absorbing  capacity,  is  of  considerable 
importance,.     There  is   perhaps   no   more  potent  disintegrator  in 
nature  than  frost,  and  it  may  be  accepted  as  fact  that  of  two  rocks 
which  are  to  be  exposed  to  frost,  the  one  most  absorbent  of  water 
will  be  the  least  durable. 

60.  Breaking  and  Crushing  Tests  possess  no  definite  value  in 
determining  upon  the  fitness  of  a  material  for  paving  purposes.     It. 
is  an  elementary  fact  in  mechanics  that  a  body  may  bear  an  enor- 
mous crushing  strain  gradually  applied  and  yet  be  readily  broken 
by  a  smart  blow  from  a  light  hammer.     Taking  the  ascertained 
breaking  and  crushing  strains  as  lying  between  3£  and  7  tons  per 
square  inch,  it  may  be  safely  said  that  no  such  strains  are  ever 
brought  to  bear  upon  any  single  inch  of  roadway  in  practice,  not 

24 


MATERIALS   EMPLOYED    IN   THE    CONSTRUCTION   OF   PAVEMENTS.     25 

even  during  the  passage  of  a  ten-ton  roller.  The  direct  pressure  or 
strain  as  applied  in  a  testing-machine  has  no  resemblance  to  the 
quick  blows  of  horses'  hoofs,  much  less  to  the  abrading  action  of 
wheels. 

61.  Methods  of  Testing  Durability.*— The  only  true  test  of  the 
fitness  of  any  material  for  paving  is  by  an  experimental  trial  upon 
a  certain  length  of  roadway  under  a  unit  of  traffic.     The  "  Rat- 
tier '  tests  now  much  employed  to  test  the  quality  of  bricks  for 
paving  do  not  fairly  represent  the  condition  of  the  materials  in  the 
pavement;  in  the  latter  the  material  is  supported  on  all  sides  but 
one,  and  is  subjected  to  pressure  and  percussion  on  this  side,  while 
in  the  "  Rattler  "  tests  the  materials  are  thrown  into  violent  colli- 
sion with  large  pieces  of  iron  weighing  anywhere  from  five  to  fif- 
teen pounds.     It  is  evident  that  under  this  treatment  the  corners- 
of  the  material  will  readily  succumb,  and  the  wear  in  consequence 
will  be  much  greater  and  of  a  different  nature  than  it  would  be 
under   actual  conditions.     The  methods  adopted  for  testing  any 
material  should  represent  as  nearly  as  possible  the  requirements  of 
practical  use. 

The  laboratory  returns  should  state: 

1.  The  technical  and  common  names  of  the  material ; 

2.  Its  geological  occurrence; 

3.  Present  use  of  the  material; 

4.  Specific  gravity; 

5.  Weathering  properties; 

6.  Resistance   to    crushing  in   the  three  conditions:  (a)  dry; 
(b)  water-soaked;  (c)  dried  after  being  subjected  to  a  freezing  and 
thawing  process. 

7.  Absorptive  properties; 

8.  Resistance  to  abrasion  ; 

9.  Character  and  cementing  qualities  of  the  detritus. 

62.  The  following  plan  of   testing   the  comparative  value  of 
paving-stones  is  adopted  at  the  Paris  Laboratory  for  Testing  Mate- 
rials.    While  it  may  be  questioned  whether  this  method  is  superior 
to  the  ' '  Rattler  "  test,  it  indicates  foreign  appreciation  of  the  fact 
that  the  "  Rattler  "  test  is  not  what  it  should  be.   The  stone  or  other 

*  See  also  Arts.  355,  1180. 


26  HIGHWAY   CONSTRUCTION. 

samples  are  clamped  to  a  horizontal  plate  revolving  round  a  verti- 
cal spindle  and  brought  to  bear  with  equal  pressure  against  a  simi- 
larly disposed  revolving  plate  of  cast-iron.  .  Along  with  the  sam- 
ples to  be  tested  is  placed  a  specimen  of  the  standard  material, 
which  is  Yvette  sandstone.  The  coefficient  of  wear  is  the  propor- 
tion between  the  volumes  worn,  which  is  ascertained  by  weighing 
the  specimens  and  determining  the  volume  from  this  weight.  The 
coefficient  for  first-class  materials  is  from  1  to  1.40,  and  for  second- 
class  materials  from  1.40  to  2.40.  If  the  wear  is  greater  than  that 
represented  by  the  coefficients,  the  material  is  rejected. 

63.  At  St.  Louis,  Mo.,  some  years  ago,  strips  of  different  pave- 
ments 22  inches  wide  and  8  feet  long  were  laid  down  as  a  test,  and 
a  two-wheeled  cart  with  tires  2  J  inches  wide,  and  loaded  to  two  tons, 
or  800  pounds  per  inch  width  of  tire,  was  rolled  back  and  forth  by 
machinery.     The  heaviest  traffic  at  that  time  in  St.  Louis  was  75 
tons  per  day  per  foot  of  width,  and  the  average  for  business  streets 
was  35  tons.    Estimating  the  effect  of  horses'  shoes  at  one  third  of 
this  amount,  50  tons  per  foot  were  taken  as  a  standard.     The  sam- 
ples were  weighed  before  and  after  testing,  and  were  subjected  to 
an  amount  of  travel  by  the  above  cart  equivalent  to  eight  and  one 
half  years  on  the  street. 

The  total  abrasion  of  the  fire-brick  pavement  was  9$,  or  a  depth 
of  }  of  an  inch,  but  about  one  half  of  the  bricks  were  broken.  As- 
phaltum  blocks  under  the  same  test  wore  14$,  and  but  one  was 
broken.  Broken  stone  lost  \%  under  a  traffic  of  12.7  tons  per  foot 
of  width.  Broken  stone  and  sand  lost  \%  under  16  tons  per  foot. 
Limestone  blocks  lost  \%  under  4400  tons  per  foot  of  width.  Wood 
blocks  lost  \%  under  12,900  tons  per  foot,  and  the  granite  blocks 
lost  \%  under  70,000  tons. 

The  action  of  the  elements  was  not  taken  into  consideration ;  it 
would  undoubtedly  increase  the  wear  of  the  several  materials. 

64.  Absorptive  Power  of  Stones,  etc. — All  materials  absorb  water 
to  a  greater  or  less  extent,  and  their  durability  is  much  affected  by 
their  absorbing  capacity.    This  capacity  depends  largely  on  the  den- 
sity, a  dense  stone  absorbing  less  than  a  light  and  more   porous 
one.     The  absorbing  capacity  is  a  matter  of  much  importance,  es- 
pecially in  cold  climates.      The  water  absorbed,  on  freezing,  tends 
by  its  expansion  to  disintegrate  the  stone.     It  has  been  said  that 
the  act  of  freezing  is  equivalent  to  the  blow  of  a  ten-ton  hammer 


1IATEKIALS    EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS.     27 

on  every  square  inch  of  surface.  Whether  this  be  so  or  not,  the 
continued  expansion  and  contraction  of  a  porous  stone  is  quite 
sufficient  to  disintegrate  it,  and  this  disintegration  will  be  the 
greater  the  more  water  the  stone  contains. 

TABLE  V. 
ABSORPTIVE  POWER  OF  STONES,  ETC. 

Percentage  of  water  absorbed, 

Granites 0.066  to  0'155 

Marbles 0.08    "    0.16 

Limestones 0.20    "     5.00 

Sandstones 0.41    "    5.48 

Brick,  common 2.00    "  25.00 

paving , 0.15    "    8.00 

Mortars 10.00    "  50.00 

Wood 0.16    "    9.00 

Asphalt Impervious 

Stones  that  have  already  begun  to  decompose  absorb  a  much 
larger  quantity  of  water  than  those  fresh  from  the  quarry,  and  de- 
cay will  be  more  rapid.  Other  things  being  equal,  the  less  the 
absorption  the  better  the  stone  or  brick. 

65.  Description  of  Materials. — Granite  is  an  unstratified  or 
igneous  rock,  composed  of  silica  or  quartz,  feldspar,  and  mica.  In 
addition  to  these  essential  constituents,  one  or  more  accessory 
minerals  may  be  present ;  the  more  commonly  occurring  are  horn- 
blende, pyroxene,  epidote,  garnet,  tourmaline,  magnetite,  pyrite, 
and  graphite.  And  the  character  of  the  rock  is  often  determined 
by  the  presence  of  these  accessory  constituents  in  quantity. 

Granite  varies  in  texture  from  very  fine  and  homogeneous  to 
coarse  porphyritic  rocks  in  which  the  individual  grains  are  an  inch 
or  more  in  length.  The  color  is  also  dependent  upon  the  min- 
erals present:  if  the  feldspar  is  the  orthoclase  (potash-spar),  it  com- 
municates a  red  color;  the  soda-spar  produces  gray.  The  mica 
also  plays  an  important  part  in  the  modification  of  color:  if  it  is  the 
white  muscovite,  it  produces  no  change;  but  if  the  black  biotite 
mica  be  present,  it  modifies  the  color  accordingly.  Hornblende 
gives  a  dark  mottled  appearance;  pyroxene  as  augite  also  gives  a 
darker  appearance;  epidote  communicates  a  green  color. 

The  durability  of  the  granites  is  closely  related  to  their  miner- 
alogical  composition.  The  presence  or  absence  of  certain  species 


28  HIGHWAY    CONSTRUCTION. 

influences  the  hardness  and  homogeneous  nature  of  the  stone.  Al- 
though popularly  regarded  as  the  most  durable  stone,  there  are 
some  notable  exceptions. 

The  quartzose,  feldspathic,  and  micaceous  granites  are  unsuit- 
able for  paving  purposes.  The  quartzose  are  too  brittle,  the  felds- 
pathic  are  too  easily  decomposed.  When  the  feldspar  is  in  excess 
the  granite  rapidly  decays  and  disintegrates  in  consequence  of  the 
action  of  air  and  water  on  the  feldspar,  the  potash  of  which  seems 
to  be  removed,  and  the  residue  falls  into  a  white  powder  composed 
chiefly  of  silica  aud  alumina.  The  micaceous  are  too  easily  lami- 
nated. 

The  term  "  granite  "  as  popularly  used  is  not  restricted  to  rock 
species  of  this  name  in  geological  nomenclature,  but  includes  what 
are  known  as  gneisses  (foliated  and  bedded  granites,  syenite, 
gabbro,  and  other  crystalline  rocks  whose  uses  are  the  same) ;  in 
fact,  the  similar  adaptability  and  use  have  brought  these  latter 
species  into  the  class  of  granites.  The  term  is  often  improperly 
applied  to  the  diabases  or  trap-rocks. 

66.  Syenite  differs  from  granite  in  having  more  hornblende, 
with  some  plagioclase,  feldspar,  and  mica,  and  little  or  no  quartz. 
(It  is  called  syenite  because  it  was  first  found  in  the  island  of 
Syene  in  Egypt.)     It  is  massive  and  its  occurrence  is  like  that  of 
granite.     It  furnishes  the  best  material  for  paving-blocks,  and  is 
better  in  proportion  to  the  darkness  of  color  and  the  predominance 
of  hornblende. 

67.  The  Sioux  Falls  stone,  much  used  for  paving  in  the  West, 
is  a  quartzite,  close-grained,  non-absorbent,  and  frost-proof.     It 
does  not  break  evenly  as  granite  and  sandstone. 

68.  The  gneiss,  quartz,  and  silicious  rocks,  though  hard,  are 
too  brittle  and  deficient  in  toughness  for  paving  purposes. 

69.  Table  VI.  shows  the  specific  gravity,  weight,  and  resist- 
ance to  crushing  of  various  granites. 


MATERIALS    EMPLOYED 


THE    CONSTRUCTION    OF    PAVEMENTS,     29 


TABLE  VI. 

SPECIFIC  GRAVITY,  WEIGHT,   AND  RESISTANCE  TO  CRUSHING  OF  VARIOUS 

GRANITES. 


Localities. 


Specific 
Gravity. 


Average  Weight, 
pounds  per 
cubic  foot. 


Resistance  to 
Crushing,  pounds 
per  square  inch. 


Kirtland  Rocks,  Conn 2.66 

Lord's  Island,  Conn. ., 

Chaumon t  Bay,  N.  Y. , 2  65 

Mystic  River,  Conn 2 . 63 

Sharkey's  Quarry,  Me 2.72 

Richmond.  Va 

Huron  Island,  Mich i 

Rockport,  Mass 2.61 

Port  Deposit,  Md 

Quincy,  Mass 2.66 

Duluth,  Minn 

Hurricane  Island,  Me 2. 67 

Mount  Sorrel,  England 2.67 

Bay  of  Fundy,  Canada 

Aberdeen,  Scotland  (gray) 2.62 

(red) 2.62 

Dublin,  Ireland 

New  Haven,  Conn 

Cornish,  Wales 2.66 

Patapsco,  Md 2. 64 


166 

162.2 
164.4 


163.2 
166.2 

166.9 
167 

163 
165 


166 
163 


35,000 
24,000 
22,700 
22,250 
22,125 
21,250 
20,650 
19,750 
19,750 
19.500 
19,000 
15,000 
12,800 
11,916 
10,900 

10,450 
9,750 
6,300 
5,340 


70.  Table  VII  shows  the  amount  of  production  and  value  of 
granite  for  street  purposes  throughout  the  United  States  for  the 
year  1889.  From  this  table  it  appears  that  the  number  of  blocks 
used  for  paving  amounted  to  nearly  62,000,000;  that  the  value  per 
thousand  varies  from  $32.22  in  Wisconsin  to  $78.67  in  Delaware. 


30 


HIGHWAY   CONSTRUCTION. 


TABLE   VII. 
PRODUCTION  AND  VALUE  OF  GRANITE  FOR  STREET  USES  IN  1889.* 


States. 

Cubic  feet, 
including 
Paving- 
blocks. 

Value, 
including 
Paving- 
blocks. 

Value 
per 
cubic 
foot. 

Number 
of 
Paving- 
blocks. 

Value 
of 
Paving- 
blocks. 

Value 

thou- 
sand. 

California      . 

3,284,232 
1,100 
567,860 
155,500 
658,603 
3,736,541 
1,051,010 
1,475,093 
338,640 
871,209 
1,157,992 
2,089,796 
247,902 
221,820 
117,400 
1,996,486 
213.477 
94,489 
601,000 
231,128 
286,946 
1,285,000 

$551,613 
230 
109,261 
67,202 
250,634 
927,949 
125,958 
466,147 
141,554 
216,986 
252,256 
236,310 
51,062 
42,605 
30,200 
368,323 
65,817 
34,016 
170,695 
48,323 
75,925 
223,825 

$0.17 
0.21 
0.19 
0.43 
0.38 
0.25 
0.12 
0.32 
0.42 
0.25 
0.22 
0.11 
0.21 
0.19 
0.26 
0.18 
0.31 
0.36 
0.28 
0  21 
0.26 
0.17 

7,303,321 

$297,236 

$40.70 

Colorado 

Connecticut  
Delaware 

761,100 
104,333 
1.599,952 
17,704,915 
286,950 
6,106,016 
1,239,000 
4,323,130 
2,043,739 
3,999,912 
587,120 
775,000 
587,000 
3,836,127 
781,765 

40,683 
8,208 
84,951 
824,113 
10,310 
378,627 
.     68,045 
216,986 
87,569 
168,555 
26,962 
34,200 
30,200 
241,793 
45,817 

53.45 
78.67 
53.10 
46.55 
35.93 
62.01 
54.  9£ 
50.19 
42.85 
42.14 
45.92 
44.13 
51.45 
63.03 
58.61 

Maryland  

Massachusetts.  .  . 
Minnesota  

New  Hampshire. 
New  Jersey  .... 

New  York  

North  Carolina.  . 
Oregon 

Pennsylvania...  . 
Rhode  Island  
South  Carolina.  . 
South  Dakota... 
Vermont  

3,017,500 
883,096 
342,895 
5,540,000 

170,694 
45,643 
18,505 
179,075 

56.57 
51.69 
53.97 
32.32 

$48.17 

Wisconsin  

Total  

20,683,244 

$4,456,891 

$0.22 

61,822,871 

$2,978,172 

llth  U.  S.  Census. 


71.  Value  of  Granite  Blocks. — In  the  most  important  States 
which  produce  paving  blocks,  namely,  California,  Maine,  Massa- 
chusetts, Missouri,  New  Jersey,  and  Pennsylvania,  the  value  varies, 
from  $40  to  something  over  $60  per  thousand.  The  variation  in 
the  price  for  these  States,  in  all  of  which  the  production  of  paving- 
blocks  has  been  going  on  for  some  time,  is  due  to  the  quality  of  the 
stone  used  for  these  purposes,  and  also  to  the  special  care  observed 
in  trimming  blocks  to  certain  definite  sizes.  In  some  localities 
surface  rock  of  inferior  quality  is  broken  up  into  paving-blocks, 
-which  are  sold  at  low  prices.  In  a  number  of  cities  considerable 


MATERIALS    EMPLOYED    IN    THE    CONSTRUCTION   OF    PAVEMENTS.     31 

care  is  taken  by  the  municipal  authorities  in  the  selection  of  the 
granite  for  paving  material.  This  care  is  exercised  both  with 
reference  to  the  quality  of  the  stone  and  to  invariability  of  size, 
and  consequently  the  price  paid  is  in  some  cases  markedly  higher 
than  that  paid  in  other  cities  more  indifferent  in  regard  to  the 
material  employed. 

72.  The  following  list  is  presented  for  the  purpose  of  showing 
the  various  uses  of  granite  for  street  and  road  construction : 

Paving-blocks.  Basin-heads. 

Curbing.  Crossing-stones. 

Flagging.  Gutter-stones. 

Crushed  for  artificial  stone;  broken  for  concrete. 

73.  Manufacture  of  Granite  Paving-blocks. — The  manufacture 
of  paving-blocks  varies  in  many  of  its  details  from  the  ordinary 
methods  of  granite-cutting.     The  high  skill  and  fine  workmanship 
of  the  stone-cutter  are  not  needed,  but  a  quickness  in  seeing  and 
taking  advantage  of  the  directions  of  cleavage,  as  well  as  a  deftness; 
in  handling  the  necessary  tools,  is  requisite. 

The  tools  used  for  making  blocks  are  knapping-hammers, 
opening-hammers,  reels,  chisels,  and  for  initial  splits  drills,  wedges,, 
and  half-rounds.  When  the  block-maker  quarries  his  own  stock  it 
is  called  "  motion  work,"  and  the  same  process  is  used  as  in  quarry- 
ing stone  for  other  purposes,  except  that,  as  large  blocks  are  not 
required,  most  of  it  can  be  done  with  plug  and  feather. 

Slabs,  having  been  split  out  in  the  usual  manner  to  sizes  that 
may  be  easily  turned  over  and  handled  by  one  man,  are  subdivided 
into  pieces  corresponding  approximately  to  the  dimensions  of  the 
required  blocks.  This  is  done  by  striking  repeated  blows  upon  the 
rock  along  the  line  of  the  desired  break  with  heavy  knapping  and 
opening  hammers.  When  a  break  is  to  be  made  crosswise  the 
grain,  it  is  frequently  necessary  to  chisel  a  light  groove  across  one 
face,  and  commonly  across  the  adjacent  sides,  to  guide  the  fracture 
produced  by  striking  on  the  opposite  surface  with  the  opening- 
hammer.  Good  splits  can,  however,  be  made  along  either  the  rift 
or  grain  by  the  skilful  use  of  the  opening-hammer  alone.  Blocks 
broken  out  in  the  manner  described  are  trimmed  and  finished  with 
the  reel,  which  is  a  hand-hammer  having  a  long,  flat  steel  head 
attached  to  a  short  handle.  Block-makers  become  very  expert  in 
the  use  of  this  tool,  and  without  making  any  measurements  turn 


32  HIGHWAY   CONSTRUCTION. 

out  in  a  surprisingly  short  time  a  large  number  of  blocks.  In 
Maine,  which  is  far  ahead  of  any  other  State  in  the  number  of 
blocks  made,  the  entire  product  of  many  quarries  is  used  for  this 
purpose  exclusively.  This  is  also  the  case  in  California,  which 
comes  second,  though  the  blocks  are  manufactured  chiefly  from  the 
surface  "boulders"  or  detached  masses  of  basalt  so  common  in 
Sonoma  County.  Other  quarries,  however,  in  various  parts  of  the 
country  utilize  only  the  "  grout,"  small  or  irregular-shaped  pieces, 
for  making  paving-blocks,  and  haul  the  stock  to  the  breakers,  who 
work  in  sheds;  but  the  greatest  number  of  blocks  are  made  on  the 
spot  where  the  rock  is  quarried,  the  workmen  being  protected 
during  the  hottest  months  by  a  temporarily  spread  canvas  fly. 

Blocks  are  counted  as  they  are  thrown  into  the  cart  which  is 
usually  needed  to  haul  them  to  the  shipping  point.  Several  paving- 
block  quarries  in  Maine  are  situated  on  steep  mountain-slopes  so 
near  water  communication  that  blocks  may  be  slid  in  long  board 
chutes  from  the  quarry  directly  into  the  hold  of  the  vessel  used 
for  their  transportation. 

Paving  breakers  seldom  work  by  the  day,  but  are  paid  a  certain 
sum  per  thousand  for  making  the  blocks;  the  price  paid  in  1889 
ranging  from  $22  to  $30  according  to  the  size  of  block  made,  kind 
of  stone  used,  locality,  and  whether  the  tools  were  furnished  and 
the  blocks  quarried  by  their  employers.  Workmen  using  their  own 
tools  are  commonly  paid  one  dollar  more  per  thousand  for  the 
blocks  made;  and  when  they  quarry  the  stock  they  use,  from  $2 
to  $5  per  thousand  is  allowed  in  addition. 

74.  Sandstones  are  rocks  made  up  of  grains  of  sand  which  are 
cemented  together  by  silicious,  ferruginous,  calcareous,  or  argilla- 
ceous material.     From  the  nature  of  the  cementing  material  the 
rocks  are  variously  designated  as  ferruginous,  calcareous,  etc.     In 
most  cases  the  cementing  material  determines  the  color.     The  va- 
rious shades  of  red  and  yellow  depend  upon  the  iron  oxides.     The 
purple  tints  are  said  to  be  due  to  oxide  of  manganese.     The  gray 
and  blue  tints  are  produced  by  iron  in  the  form  of  ferrous  oxide  or 
carbonate. 

75.  The  hardness,  strength,  and  durability  depend  upon  the 
nature  of  the  cementing  material.     If  the  cementing  material  be 
one  which  decomposes  readily,  as  in  the  argillaceous  and  calcareous 
varieties,  the  whole  mass  is  soon  reduced  to  sand. 


MATERIALS   EMPLOYED   IN   THE    CONSTRUCTION    OF    PAVEMENTS.     33 


76.  Sandstones  are  widely  distributed,  and  they  represent  all  of 
the  geological  periods,  from  the  oldest  to  the  most  recent  forma- 
tions. 

77.  The  sandstones  obtained  from  the  Upper  Silurian  and  the 
Lower  Carboniferous  formations  are  much  used  in  the  form  of  blocks 
for  street  paving  in  the  Lake  and  Western  cities.     They  are  durable 
and  do  not  become  smooth  or  slippery  when  wet,  but  in  the  form 
of  fragments  for  broken  stone  roads  they  are  useless. 

78.  Hudson  Eiver  Bluest  one. — The  term  "  Hudson  Eiver  blue- 
stone  "  is  used  to  designate  the  blue,  fine-grained,  compact,  and 
even-bedded  sandstone  which  is  so  largely  employed  for  flagging 
and  curbing  in  the  cities  and  towns  of  New  York  and  neighboring 
States. 

The  color  is  predominantly  dark  gray  and  hence  (more  by  con- 
trast with  the  red  sandstone)  a  "  bluestone." 

In  texture  the  range  is  from  the  fine  shaly  or  argillaceous  to 
the  highly  silicious  and  even  conglomerate  rock. 

The  best  bluestone  is  rather  fine-grained  and  not  very  plainly 
laminated,  and  its  mass  is  nearly  all  silica  or  quartz  which  is  ce- 
mented tegether  by  a  silicious  paste  and  contains  very  little  argil- 
laceous  matter. 

It  is  so  compact  as  not  to  absorb  moisture  to  any  extent,  and 
hence  soon  dries  after  rain  or  ice;  it  has  the  hardness  to  resist 
abrasion  and  wears  well;  it  is  even-bedded  and  thus  presents  a  good 

TABLE  VIII. 
ANALYBES  OP  SANDSTONE. 


05 

l| 

& 

Kind  of 
Stone. 

Locality. 

i 

2 

M 

!«5 

I 

c3 

"3 

t£ 

X 

QQ 

M 

£& 

£ 

§ 

S 
0 

50 

« 

e 

1 

0 

Ed 

CO 

j 

3 

H 

£ 

00 

°^ 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.  ct. 

p.ct. 

Manyard.... 
Worcester.  . 

(E.  Long:-) 
•<  meadow,  > 

79.38 
88.89 

8.75 
5.95 

2.43 
1.79 

(i'4i 

2.57 
0.27 

.... 

4. 
0. 

08 
86 

2.79 

1.83 

Kibbie 

f     Mass      f 

81  38 

9  44 

3  54 

0  11 

0  76 

6  28 

4.49 

Brownstone 
Sandstone.. 
Quartzite  
Buff  

Portland,  Conn. 
Stony  Ft.,  Mich. 
Pipestone,  Minn 
Amherst,  Ohio. 

69.94 
84  57 
84.52 
97.00 

13.15 
5.90 
12.33 

2.48 
6.48 
2.12 
1.00 

0.70 

3.09 

OM 
1.15 

Trace 
0.68 
Trace 

3.30 
Unde 
0.11 
0. 

5.48 
ter'd 
0.34 
64 

1.01 
1.92 
2.31 
0.21 

Berea  

Berea,  Ohio. 

96.90 

1.68 

0.55 

0. 

55 

0.32 

Euclid  Co    Ohio 

95  00 

2  50 

1  00 

1.50 

Columbia  

Columbia,  Ohio. 

96.50 

1.00 

0. 

50 

2.00 

Red 

94  00 

Trace 

1  90 

1.10 

i.oo 

1.99 

Elyria  
Sandstone  

3rafton,  Ohio. 
Fond  du  Lac,  Mn. 

87.66 

78.24 

1.72 
10.88 

3.52 
3.83 

0.17 
0.95 

0.20 
1.60 

1.67 

'006 

2.03 

34 


HIGHWAY   CONSTRUCTION. 


smooth  natural  surface,  and  it  has  a  grain  which  prevents  it  from 
becoming  slippery;  it  is  not  materially  affected  by  freezing  and 
thawing;  it  is  strong  and  not  apt  to  get  broken  if  well  laid. 

79.  Commercial  Names  of  Sandstone. — The   commercial  names 
of  sandstone  are  usually  obtained  from  places  where  it  is  quarried, 
as,  Berea,  Grit,  Medina,  etc. 

80.  Table  VIII  on  the  opposite  page,  giving  analyses  of  sandstone 
frcm  a  number  of  localities,  will  serve  to  indicate  its  general  com- 
position. 

81.  The  specific  gravity,  weight,  and  resistance  to  crushing  of 
various  sandstones  is  given  in  Table  IX.     The  amount  of  produc- 
tion and  value  of  sandstone  for  street  purposes  in  the  United  States 
in  1889  is  given  in  Tables  X  and  XI. 

TABLE  IX. 

SPECIFIC  GRAVITY,  WEIGHT,  AND  RESISTANCE  TO  CRUSHING  OP  VARIOUS 

SANDSTONES. 


Localities. 


Specific 
Gravity. 


Average  Weight, 
pounds  per 
cubic  foot. 


Resistance  to 
Crushing,  pounds 
per  square  inch. 


Potsdam  (red),  K  Y 2. 60 

Medina,  N.  Y 

Maiden  (bluestone),  K  Y 2.75 

Warsaw  ( bluestone),  N.  Y 2 . 68 

Albion,  N.  Y 

Craigleith,  Scotland 2 . 45 

Belleville,  N.  J 2.56 

Kasota,  Minn . . . 
Seneca,  Ohio. . . 

Berea,  Ohio 2. 57 

Little  Falls,  N.Y. 

Dorchester,  New  Brunswick.. . . 

Vermilion,  Ohio. 

Massillon,  Ohio. . 

Cleveland,  Ohio. 

Abroath  (pavement),  England. .          2.47 

Marquette,  Mich 2.53 

Middletown  (Portland),  Conn...          2.62 
North  Amherst.  Ohio. 

Oxford  (bluestone),  N.  Y 2.71 

Fond  du  Lac,  Wis 

Bristow,  Va 2.61 

Yorkshire,  England 2 . 51 

Warrensburg,  Ohio. 
Haverstraw,  N.  Y.. 

Derby  Grit,  England 2.4 

Cheshire  (red),  England. .......          2.15 

Nova  Scotia 2.62 


162.28 

171.47 
167.10 

153 
159.67 


160.06 


155 

158.17 

163.43 

168,9 

163 
157 


150 
133 
163.50 


42.804 
17,725 


13,500 

5,287 

11,700 

11,675 

10,500 

10,250 

9,850 

9,412 

8,850 

8,750 

7,910 

7,884 

7,450 

6,950 

6.650 

13,472 

6,250 

5,714 
5,000 
4,350 
3,100 
2,185 


MATERIALS   EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS. 


TABLE  X, 

PRODUCTION  AND  VALUE  OF  SANDSTONE  FOR  STREET  USES  IN  1889,  BY 
STATES  AND  TERRITORIES.* 


States  and  Territories. 

Cubic  Feet. 

Value. 

Value  per 
cubic  foot. 

27,160 

8  215 

0  30 

100 

200 

2  00 

Colorado  

1  926  464 

509  955 

0  26 

Connecticut  

40  500 

2*250 

0  06> 

Illinois     

3  200 

50 

0  025 

8  840 

880 

0  10> 

452,015 

132  188 

0.29 

Kentucky                    .  .           

13  900 

1  600 

0  12 

40320 

2  045 

0  05- 

501,221 

40471 

0.08- 

Michigan     .  .                     .  .       

2496 

550 

0  22 

Minnesota  

51  930 

38200 

0  74 

6,533 

2  512 

0.38 

New  Mexico.  

10,000 

3,000 

0.30 

New  York           .  .           

2  864  366 

459  158 

0  16 

Ohio     

1,603  614 

430  552 

0.27 

854,907 

175,062 

0.20* 

^Vest  Virginia                      .  . 

42075 

23  274 

0-55 

Florida,    Georgia,    Nevada,    Rhode 
Island,  Vermont  

13,865 

2660 

0.19 

Total  

8  463,506 

$1  832,822 

$0.22 

• 

*llth  U.  S.  Census. 


TABLE  XI. 
PRODUCTION  AND  VALUE  OF  "BLUESTONE"  FOR  STREET  USES  IN 


States. 

Cubic  Feet. 

Value. 

Value  per 
cubic  foot. 

15,649 

8,550 

0.55 

New  York     .     

2,357,724 

475,403 

0.20- 

Pennsylvania  

786,513 

265,959 

0.34 

Total.. 

3,159,886 

$749,912 

$0.24 

82.  Limestone. — Limestone  is  essentially  carbonate  of  lime,  out 
it  always  contains  some  additional  constituent ;  the  more  commonly 
occurring  impurities  or  accessory  matters  are  silica  in  the  form  of 


3G  HIGHWAY    CONSTRUCTION". 

quartz,  clay,  iron,  magnesia,  etc.  And  limestones  are  said  to  be 
silicious,  argillaceous,  ferruginous,  magnesian,  dolomitic,  bitumi- 
nous, etc.,  according  as  they  contain  one  or  another  of  these  con- 
stituents. Other  foreign  mineral  matter  may  be  found  in  them, 
and  in  such  quantity  as  to  give  character  to  the  mass. 

In  color  there  is  a  wide  variation,  depending  upon  the  impu- 
rities; it  ranges  from  the  white  of  the  more  nearly  pure  carbonate 
of  lime  through  gray,  blue,  yellow,  red,  brown,  and  to  black. 

The  texture  also  varies  greatly;  it  may  be  coarse  or  fine.  The 
fcerms  coarse-grained  and  fine-grained  are  applied  when  the  mass 
resembles  sandstone  in  its  granular  aggregations.  Other  terms, 
as  saccliaroidal  (like  sugar),  oolitic,  crinoidal,  etc.,  are  also  used  to 
describe  the  texture.  The  state  of  aggregation  of  the  constituent 
particles  varies  greatly,  and  the  stone  may  be  hard  and  compact, 
almost  vitreous,  or  loosely  cemented  and  crumbling  with  slight 
pressure,  like  sugar,  or,  again,  like  chalk,  dull  and  earthy. 

From  this  general  statement  of  the  range  in  composition  and 
texture,  it  follows  that  there  is  an  equally  wide  variation  in  hard- 
ness, strength,  and  durability  of  limestones.  Some  are  hard  and 
strong,  surpassing  in  their  resistance  to  crushing  force  many  gran- 
ites, and  nearly  as  durable  as  the  best  sandstone;  others  are  friable 
and  fall  to  pieces  under  slight  pressure,  or  they  are  disintegrated 
rapidly  by  atmospheric  agents. 

83.  The  limestones  are  used  for  flagging  and  curbing,  being- 
selected  for  these  purposes  on  account  of  accessibility  or  cheapness. 
For  broken-stone  roads  with  light  traffic  the  limestones  are  emi- 
nently suitable;  they  possess  the  quality  of  forming  a  mortar-like 
detritus  which  binds  the  stones  together  and  enables  them  to  wear 
better  than  a  harder  material  that  does  not  bind.     For  this  purpose 
the  most  suitable  ones  are  the  silicious,  magnssian,  dolomitic,  and 
bituminous. 

84.  The  experience  of  all  cities  using  paving-blocks  of  lime- 
stone is  that  it  wears  unevenly,  and  in  a  year  or  two  the  blocks  are 
shivered  and  split  by  the  action  of  frost. 

Table  XII  shows  the  specific  gravity,  weight,  and  resistance  to 
crushing  of  various  limestones.  Table  XIII  shows  the  production 
and  value  of  limestone  for  street  uses  in  1889,  by  States  and  Terri- 
tories. 


MATERIALS    EMPLOYED    IK    THE    CONSTRUCTION    OF    PAVEMENTS.     37 


TABLE  XII. 

SPECIFIC  GRAVITY,  WEIGHT,  AND  RESISTANCE  TO  CRUSHING  OF  VARIOUS 

LIMESTONES. 


Localities. 

Specific 
Gravity. 

Average 
Weight, 
pounds  per 
cubic  foot. 

Resistance  to 
Crushing, 
pounds  per 
square  inch. 

Joliet  111     

1fi  QOO 

2.69 

168 

16  250 

North  River   NY       

2  71 

169 

1Q  4.OS; 

10  «nn 

Glens  Fulls   N.  Y  

2  70 

169 

11  475 

JVIarquette,  Mich     

8  050 

Billingsville,  Mo  

7  250 

3  650 

Pur  heck   England        .  .  . 

2  6 

162 

Q  1fiO 

Anglesea,        "       

7  579 

2  467 

154 

TABLE  XIII. 

PRODUCTION  AND  VALUE  OF  LIMESTONE  FOR  STREET  USES  IN  1890,  BY 
STATES  AND  TERRITORIES.* 


Cubic  Feet. 

Value. 

Value  per 
cubic  foot. 

Alabama  

98,000 

9,800 

0  10 

2  000 

500 

0  25 

35000 

1  390 

0  04 

Illinois  

10  221,392 

505,576 

0.05 

2  614  862 

316  722 

0  12 

1  707  931 

53  641 

0.03 

Kansas  

771,041 

97,502 

0.13 

Kentucky  

1  762  711 

86  054 

0.05 

145  670 

6750 

0.05 

Michigan  

485,377 

18,156 

0.04 

Minnesota  ,         ... 

68  788 

11,778 

0.17 

11  542  723 

670,351 

0.06 

Nebraska  

1,926,469 

86,643 

0.04 

New  York  

5  241  262 

197,091 

0.04 

Ohio  

7  236  981 

183,235 

0.03 

Pennsylvania  

2,042,804 

72,512 

0.04 

Tennessee  

14500 

3,400 

0.23 

Texas  

67,750 

32,278 

0.48 

Vermont,     .  .                   .... 

9990 

2,098 

0.21 

Virginia  

7,560 

190 

O.OS 

Wisconsin  

488,811 

27,789 

0.06 

Total  

46,491,622 

$2,383,456 

$0.05 

*  llth  U.  S.  Census. 

85.  The  material  called  Ligonier  "  Granite,"  which  is  exten- 
sively used  for  paving,  etc.,  is  a  silicious  limestone  from  localities 


HIGHWAY   CONSTRUCTION. 


near  Pittsburg,  and  is  said  to  have  a  crushing  strength  of  23,000 
pounds  per  square  inch. 

86.  Trap-rock  is  the  common  name  given  to  a  large  group  of 
lunstratified  eruptive  or  igneous  rocks.     They  are  composed  of  feld- 
spar (usually  labradorite),  augite,  hornblende,  and  some  magnetite 
iind  i  itanic  iron. 

The  term  trap  is  derived  from  trappa,  a  Swedish  word  for  stair, 
because  the  rocks  of  this  class  frequently  occur  in  largo  tabular 
masses  rising  one  above  the  other  like  steps,  as  seen  on  the  west 
shore  of  the  Hudson  Eiver  from  Jersey  City  to  Haverstraw.  The 
various  proportions  and  states  of  aggregation  of  the  simple  minerals, 
arid  their  differences  in  external  forms,  give  rise  to  many  varieties 
— such  as  dolorite,  which  depends  for  its  hardness  upon  silica  and 
feldspar,  and  may  be  either  light  or  dark  colored.  Basalt  is  one  of 
the  most  common  varieties;  it  is  of  a  dark  green,  gray,  or  black 
color,  is  composed  of  augite  and  feldspar,  very  compact  in  texture 
and  of  considerable  hardness,  it  often  contains  iron,  whence  the  name 
basalt,  an  Ethiopian  word  for  iron.  Greenstone,  another  variety,  is 
composed  of  hornblende  and  feldspar  and  is  of  a  dark  green  color. 

The  trap-rocks  are  hard  and  tough,  have  no  true  cleavage,  and 
break  irregularly;  they  are  difficult  to  work.  But  there  is  much 
variation  in  the  stones  of  different  localities.  The  rock  of  the  Pali- 
sades in  New  Jersey  splits  easily  into  biocks,  and  has  been  exten- 
sively used  for  paving  in  New  York,  Brooklyn,  and  Jersey  City, 
under  the  name  of  "  Belgian  block;"  but  since  the  introduction  of 
granite  for  this  purpose  their  use  has  considerably  decreased. 

The  trap-rocks  are  exceedingly  durable  and  eminently  suitable 
for  broken-stone  roads,  but  for  paving-blocks  they  are  a  failure. 

87.  Table  XIV  shows  the  crushing  resistances,  specific  gravity, 
and  weight  of  trap-rocks. 

TABLE  XIV. 
CBUSHING  RESISTANCE,  SPECIFIC  GRAVITY,  AND  WEIGHT  OF  TRAP-ROCKS. 


Locality. 

Resistance  to 
Crushing,  pounds 
per  square  inch. 

Specific 
Gravity. 

Weight  of  one 
cubic  foot, 
pounds. 

Staten  Island   N.  Y     . 

22  2oO 

2  86 

178  8 

20,750  to  22  250 

3  03 

189  5 

Palisades  N   J     . 

19  700 

MATERIALS    EMPLOYED    IN    THE    CONSTRUCTION    OF    PAVEMENTS.     39 

88.  Bitumen,  Asphaltum,  Asphalt.— Bitumen  is  the  name  used 
to  denote  a  group  of  mineral  substances,  composed  of  different  hy- 
drocarbons, found  widely  diffused  throughout  the  world  in  a  variety 
of  forms  which  grade  from  thin  volatile  liquids  to  thick  semi-fluids 
and  solids,  sometimes  in  a  free  or  pure  state,  but  more  frequently 
intermixed  with  or  saturating  different  kinds  of  inorganic  or  organic 
matter. 

88a.  To  designate  the  condition  under  which  bitumen  is  found 
different  names  are  employed;  thus  the  liquid  varieties  are  known 
as  naphtha  and  petroleum,  the  semi-fluid  or  viscous  as  maltha  or 
mineral  tar,  and  the  solid  or  compact  as  asphaltum  or  asphalt. 

89.  Three    distinct    varieties    of  asphaltum    are    recognized, 
namely,  the  earthy,  the  elastic,  and  the  hard  or  compact. 

89a.  The  earthy  variety,  represented  by  the  chapopota  of 
Mexico,  Colombia,  and  other  parts  of  South  America,  has  a  brown- 
ish-black dull  color,  an  earthy  uneven  fracture,  when  freshly  ex- 
cavated a  strong  though  not  unpleasant  earthy  odor,  is  soft  enough 
to  take  an  impression  of  the  nail,  hardens  slightly  on  exposure  to 
the  atmosphere,  and  burns  with  a  clear  brisk  flame,  emitting  a 
powerful  odor,  and  depositing  much  soot. 

89b.  Elastic  asphaltum  is  of  various  shades  of  brown;  is  soft, 
flexible,  and  elastic;  it  has  an  odor  strongly  bituminous,  and  is  of 
about  the  density  of  water;  it  burns  with  a  clear  flame  and  much 
smoke.  Like  caoutchouc,  it  takes  up  pencil  marks,  and  on  this 
account  is  called  mineral  cauotchouc ;  it  has  been  found  only  at 
three  places:  in  the  fissures  of  a  slaty  clay  at  Castleton,  England; 
at  Montrelais,  France;  and  in  Massachusetts. 

89c.  Hard  or  compact  asphaltum  is  the  most  useful  variety;  it 
forms  large  deposits  in  many  parts  of  the  world,  and  is  of  various 
degrees  of  quality,  according  to  its  age  and  the  impurities  mixed 
with  it;  when  nearly  pure  its  ordinary  characteristics  are  as  follows: 
Color  brownish  black  and  black;  lustre  resinous  or  coal-like; 
opaque.  At  temperatures  below  100°  F.  it  is  brittle  and  breaks 
with  a  conchoidal  fracture.  Melts  ordinarily  at  190°  F.  to  195°  F., 
and  is  liquid  at  about  212°  F.  At  212°  F,  it  has  a  peculiar  but 
agreeable  aromatic  odor,  somewhat  resembling,  but  still  very  differ- 
ent from,  that  of  coal  tar;  at  ordinary  temperatures  the  odor  is 
.scarcely  perceptible,  but  when  rubbed  it  is  quite  strong.  It  kindles 


40  HIGHWAY    CONSTRUCTION'. 

readily  and  burns  brightly  with  a  thick  smoke.  Distilled  by  itself 
it  yields  a  bituminous  oil  of  a  yellow  color  (consisting  of  hydrocar- 
bons mixed  with  oxidized  matter),  water,  some  combustible  gases, 
and  sometimes  traces  of  ammonia. 

After  combustion  it  leaves  about  one  third  of  its  weight  of  char- 
coal and  ashes  containing  silica,  alumina,  oxide  of  iron,  sometimes 
oxide  of  manganese,  lime,  and  other  inorganic  and  organic  matter. 
Its  composition  and  hardness  are  variable. 

Specific  Gravity. — Pure  bitumen  has  a  density  less  than  water; 
but  in  consequence  of  the  impurities  mixed  with  it  the  specific 
gravity  of  asphaltum  varies  from  1.0  to  1.7.  Solubility:  It  is 
insoluble  in  water,  partly  or  wholly  soluble  in  chloroform  and 
disulphide  of  carbon,  partly  or  wholly  in  oil  of  turpentine  and 
petroleum  ether,  and  commonly  partly  in  alcohol. 

90.  By  different  solvents  asphaltum  may  be  decomposed  into 
three  distinct  though  complex  substances  which  have  been  named 
by  Boussingault  and  other  chemists  who  have  investigated  it 
petrolene,  asphaltene,  and  retine.  Nothing  definite  is  known 
concerning  these  compounds  or  how  their  variable  proportions  and 
composition  affect  the  quality  of  an  asphaltum.  In  the  past  they 
have  received  but  little  attention  from  chemists,  due  probably  to 
the  limited  use  of  asphaltum;  but  now,  in  view  of  its  large  and 
increasing  employment  for  paving  and  other  industrial  purposes, 
their  investigation  offers  a  wide  and  undoubtedly  profitable  field 
for  chemical  research. 

90a.  The  characteristics  of  these  compounds,  so  far  as  known, 
are  generally  as  follows: 

Petrolene  is  the  compound  which  is  considered  to  give  the  vis- 
cous or  adhesive  quality.  It  may  be  described  as  that  portion  of 
the  bitumen  which  is  soluble  in  petroleum  ether.  It  is  lighter  than 
water,  very  combustible,  and  has  a  high  boiling-point,  pale  yellow 
color,  and  peculiar  odor.  On  evaporating  off  the  ether  it  remains 
as  a  resin  with  a  brownish-black  color,  which  dissolves  readily  in 
the  volatile  oils.  Its  composition  is  carbon,  hydrogen,  and  sulphur. 
The  amount  present  in  an  asphaltum  is  variable,  ranging  from  3  to 
70  per  cent  of  the  weight  of  the  asphaltum.* 

*  It  has  been  found  that  a  bitumen  suitable  for  paving  purposes  should, 
contain  at  least  70  per  cent  of  petrolene. 


MATERIALS    EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS.     41 

Asphaltene  is  the  compound  which  gives  the  hardness  to  as- 
phaltum.  It  contains  the  elements  of  petrolene,  together  with  a 
quantity  of  oxygen,  and  probably  arises  from  the  oxidation  of  that 
compound.  It  is  that  portion  of  the  bitumen  which  is  insoluble 
in  ether.  It  is  dissolved  out  by  carbon  disulphide,  chloroform, 
benzene,  etc.  Its  color  is  a  brilliant  black;  density  greater  than 
water.  It  burns  like  resins  in  general,  leaving  a  very  abundant 
coke.  Like  petrolene,  it  is  composed  of  carbon,  hydrogen,  and 
oxygen,  and  the  amount  present  in  an  asphaltum  is  as  variable — 
ranging  from  1  to  about  60  per  cent. 

Retine  is  dissolved  out  by  alcohol  (anhydrous)  from  that  por- 
tion of  the  asphaltum  which  is  unaffected  by  the  solvents  above 
mentioned.  It  is  a  yellow  resin  composed  of  carbon,  hydrogen, 
and  sulphur.  What  effect  this  compound  has  upon  asphaltum  is 
unknown.  Some  authorities  claim  that  its  presence  is  injurious. 

91.  Origin  of  Bitumen. — The  origin  of  bitumen  is  unknown.    It 
is  supposed  to  be  the  ultimate  product  resulting  from  the  destruc- 
tion under  certain  conditions  of  the  organized  remains  of  animals 
and  vegetables,  producing  (1)  naphtha,  (2)  petroleum,  (3)  maltha 
or  mineral  tar,  (4)  asphaltum.      The  whole   of  these   substances 
merge  into  each  other  by  insensible  degrees,  so  that  it  is  impossible 
to  say  at  what  point  maltha  ends  and  asphaltum  begins.    Naphtha, 
the  first  of  the  series,  is  in  some  localities  found  flowing  out  of  the 
earth  as  a  clear,  limpid,  and  colorless  liquid;  as  such  it  is  a  mix- 
ture of  hydrocarbons,  some  of  which  are  very  volatile  and  evapo- 
rate on  exposure.     It  takes  up  oxygen  from  the  air,  becomes  brown 
and  thick,  and  in  this  condition  it  is  called  petroleum. 

Ola.  The  hardening  of  the  bituminous  fluids  which  have  oozed, 
out  or  been  exposed  by  other  causes  upon  the  surface  of  the  earth 
seems,  in  most  cases  at  least,  to  have  resulted  from  the  loss  of  the 
vaporizable  portions,  and  also  from  a  process  of  oxidation  which 
consists,  first,  in  a  loss  of  hydrogen,  and  finally  in  the  oxygenation 
or  evaporation  of  the  more  volatile  portions,  which  gradually  trans- 
forms them  into  mineral  tar  or  maltha,  and,  still  later,  into  solid 
glossy  asphaltum,  of  which  gilsonite,  wurtzilite,  uintahite,  etc., 
are  examples. 

92.  Occurrence   and  Distribution  of  Asphaltum.— Deposits  of 
asphaltum  are  found  widely  diffused  throughout  the  world,  and  at 


42  HIGHWAY   CONSTRUCTION. 

various  altitudes  ranging  from  below  sea-level  to  thousands  of  feet 
above.  It  is,  however,  seldom  found  among  the  primitive  or  older 
rock  formations,  but  seems  to  belong  exclusively  to  the  secondary 
and  tertiary  formations.  Intermixed  with  the  argillaceous  stratas, 
it  forms  extensive  beds  or  lakelike  deposits  on  both  continents,  the 
most  remarkable  of  which  are  those  situated  in  the  "West  Indies 
and  South  America.  The  most  notable  of  these  are  the  so-called 
pitch  lakes  on  the  island  of  Trinidad,  and  at  Bermudez,  Venezuela. 

92a.  Saturating  the  calcareous  and  sandstone  formations,  it 
forms  large  subterraneous  deposits  in  Europe  and  the  United 
States.  The  calcareous  varieties  occur  more  extensively  in  Europe 
than  in  America,  and  are  the  source  of  the  material  employed 
there  for  street-paving  under  the  name  of  asphalte.  The  sand- 
stone class  is  found  extensively  in  the  Western  and  Southwestern 
States,  especially  in  California,  Texas,  Kentucky,  and  the  Indian 
Territory. 

92b.  In  a  free  or  nearly  pure  state  it  is  found  in  veins  and 
seams  in  the  primitive  rock  and  volcanic  formations.  This  class  of 
deposit  is  rare  and  the  amount  of  asphaltum  is  generally  insignifi- 
cant. A  notable  exception,  however,  are  the  deposits  of  Utah,  etc. 
The  mines  from  which  gilsonite,  wurtzilite,  uintahite  are  produced 
are  said  to  be  very  extensive,  and  the  material  is  very  nearly  pure. 
Similar  deposits  are  found  in  Mexico,  Cuba,  and  various  parts  of 
South  America. 

92c.  In  many  localities  beds  of  shale,  sand,  and  cretaceous  lime- 
stone are  found  saturated  with  maltha,  from  which  the  bitumen  is 
extracted  by  boiling  or  macerating  with  water. 

92d.  From  the  variety  of  the  deposits  and  their  manner  of 
occurrence  it  seems  that  asphaltum  belongs  to  no  particular  era 
or  age.  Moreover,  the  asphaltum  obtained  from  these  different 
sources  is  not  uniform  either  in  character,  appearance,  hardness, 
or  chemical  composition.  The  ultimate  composition  of  specimens 
from  several  localities  is  given  in  Table  XIV#. 

93.  Nomenclature. — As  indicated  above,  the  varieties  of  bitumen 
and  asphaltum  are  as  numerous  as  the  localities  producing  them; 
hence  there  is  a  great  variety  of  names  used  to  designate  the 
same  substance  which  is  oftentimes  misleading,  if  not  confusing. 
As  an  illustration  of  this  variety  the  following  may  be  mentioned: 


MATERIALS   EMPLOYED    IN   THE    CONSTRUCTION"   OF    PAVEMENTS.     43 


native   pitch,   mineral   pitch,   glance   pitch,  grahamite,  albertite, 
piauzite,  elaterite,  gilsonite,  wurtzilite,  uintahite,  turrellite. 

TABLE   XIV«. 
COMPOSITION  OP  THE  BITUMEN  OF  VARIOUS  ASPHALTS. 


-.] 

[n  Extract* 

;d  Bitumen 

Sulphur. 

Carbon. 

Hydro- 
gen. 

Nitrogen. 

Trinidad  (Lake)  

Hard 

6.16 

82.33 

10.69 

0.81 

California  (Waldorf)  

6.48 

82.77 

10.62 

0.35 

"         (La  Patera)  

6.23 

83.30 

9.88 

0.70 

Texas  (Uvalde)  

9.60 

80.32 

10.09 

0.28 

Cuba  (Bejucal)  

8.52 

80.87 

10.42 

0.19 

Utah  (Gilsouite)  

1.79 

89.28 

8.66 

0.79 

Kentucky          

Medium 

3.39 

84.16 

11.52 

1.58 

Indian  Ter.  (Cbickasaw)  .  .  . 
"         "     (Ardmore) 
California  (Alcatraz)  

Soft 

1.98 
1.47 
1.32 

85.65 

87.40 

85.72 

12.37 
11.05 
11.83 

6  '.65 
1.21 

Bermudez  (Venezuela)  

5.87 

82.88 

10.70 

0.75 

93a.  Sometimes  the  name  of  the  locality  where  it  is  found  is 
used  as  a  prefix  and  is  thus  useful  to  indicate  the  source.  Such 
names  are  Dead  Sea  bitumen,  Egyptian  asphalt,  Cuban,  Trinidad, 
Bermuda,  California:!,  Kentucky,  etc. 

93b.  The  name  asphalte  has  been  adopted  by  the  French 
to  designate  the  material  obtained  from  their  bituminous  limestone 
deposits,  and  is  now  generally  employed  throughout  Europe  to 
denote  both  the  carbonate  of  lime  impregnated  with  asphaltum 
and  the  pavement  made  from  that  material. 

93c.  The  name  lithocarbon  has  been  recently  adopted  to 
designate  a  cretaceous  limestone  saturated  with  bitumen  found  in 
Texas. 

93d.  Some  authorities  apply  the  terms  asphaltum,  asphalt,  and 
liquid  asphalt  to  the  semi-fluid  and  viscous  bituminous  substance 
or  maltha,  which  by  heat  may  be  transformed  into  asphaltum. 
This  application  seems  to  be  erroneous,  because  asphaltum  techni- 
cally means  bitumen  in  the  solid  form.  Others  use  the  same  terms 
to  designate  the  entire  mixture  of  bitumen,  mineral  and  organic 
matter,  while  others  apply  them  to  denote  the  purified  material. 

94.  The  names  which  seem  to  be  the  most  used  in  the  United 


44  HIGHWAY   CONSTRUCTION. 

States  and  which  are  at  the  same  time  descriptive  of  the  various 
classes  are  as  follows  : 

Crude  asphaltum  or  crude  asphalt  is  applied  to  all  mixtures 
of  bitumen,  clay,  sand,  etc.;  e.g.,  crude  Trinidad  asphalt. 

Refined  asplidltum  or  asphalt  is  used  to  denote  the  asphaltum 
after  it  has  been  wholly  or  partly  freed  from  the  combined  organic 
and  inorganic  matters,  J 

The  limestone  rocks  impregnated  with  bitumen  are  called 
bituminous  or  asphaltic  limestones.  The  term  rock  asphalt  is 
also  applied  to  the  same  material,  the  name  of  the  source  being  also 
used,  as  "Italian  rock  asphalt,"  "Val  de  Travers  rock  asphalt," 
etc. 

The  sandstones  containing  bitumen  are  known  as  bituminous  or 
asphaltic  sandstones,  the  name  of  the  source  being  also  mentioned. 

The  semi-fluid  bitumen  is  designated  by  the  names  maltha 
and  mineral  tar. 

The  term  asphalt  is  also  frequently  but  erroneously  applied 
to  various  preparations  in  which  the  cementing  material  is  coal  tar 
or  the  residue  of  oil-refineries,  etc. — substances  which  are  entirely 
dissimilar  to  asphaltum.  though  apparently  possessing  some  of  its 
characteristics. 

The  term  bitumen  is  employed  to  designate  the  truly  bitumi- 
nous portion  of  the  asphaltum  and  its  compounds.* 

95.  Refined  Asphaltum  is  asphaltum  freed  from  the  combined 
water  and  accompanying  inorganic  and  organic  matter.  By  com- 
paratively simple  operations  the  several  varieties  of  asphaltum  may 
be  reduced  to  an  equal  state  of  purity. 

95a.  The  argillaceous  varieties,  such  as  Trinidad,  Bermt.'dez, 
etc.,  are  purified  in  iron  vessels  by  the  application  of  heat  either 
directly  from  fire  or  indirectly  by  steam,  the  temperature  em- 

*  Manjak  is  the  name  given  to  the  asphaltum  found  in  the  Island  of  Bar- 
badoes.  Its  composition  is : 

Volatile  organic  matter 70.85 

Non-volatile  organic  matter 26.97 

Mineral  matter 0.18 

Moisture..            ....  2.00 


100.00 


NATE  RIALS    EMPLOYED    IN   THE    CONSTRUCTION"    OF    PAVEMENTS.      45 

ployed  ranges  from  212°  F.  to  350°  F.  During  the  application  of 
the  heat,  the  asphaltum  is  liquefied  the,  combined  water  is  evapor- 
ated, the  organic  matters  rise  to  the  surface  and  are  skimmed  off, 
and  the  inorganic  settle  to  the  bottom  of  the  vessel;  when  the 
liberation  of  the  impurities  is  completed,  the  liquid  asphaltum  is 
•drawn  off  into  barrels  and  constitutes  the  refined  asphaltum  of 
commerce. 

95b.  The  calcareous  and  silicious  varieties  are  purified  by  boil- 
ing or  macerating  them  with  hot  water,  according  to  the  freedom 
with  which  they  part  with  the  intermixed  impurities.  During  the 
action  of  the  water  the  sand  and  other  ingredients  fall  to  the  bottom 
.of  the  vessel,  and  the  bitumen  rises  to  the  surface  or  forms  clots  on 
the  sides  of  the  boiler,  whence  it  is  skimmed  off  and  thrown  into 
another  boiler,  where  it  is  boiled  for  some  time,  during  which  the 
water  and  more  volatile  oils  are  evaporated,  and  the  mineral  matters 
.still  retained  fall  to  the  bottom,  leaving  the  bitumen  in  the  form  of 
a  thick  viscid  substance,  in  which  state  it  is  used  in  several  of  the 
arts.  By  continuing  the  boiling  for  a  considerable  time  or  by 
increasing  the  temperature  to  about  250°  F.  the  volatile  portions 
are  driven  off  and  the  viscid  bitumen  is  brought  to  a  condition 
which  upon  cooling  causes  it  to  become  solid. 

95c.  The  operation  of  refining  or  purifying,  while  exceedingly 
simple,  requires  to  be  performed  with  much  care,  for  the  reason  that 
if  the  asphaltum  is  melted  at  too  high  a  temperature  it  will  be 
burned  or  coked,  or  if  the  heating  is  prolonged  at  a  low  tempera- 
ture the  result  will  be  practically  the  same.  In  either  case  the 
petrolene  is  converted  into  asphaltene. 

96.  Asphaltic  Cement. — Asphaltum  in  a  refined  or  pure  state 
is  valueless  as  a  cementing  medium,  owing  to  its  hardness,  brittle- 
ness,  and  lack  of  cementitious  properties;  therefore  it  is  necessary 
to  add  some  substance  which  will  impart  to  it  the  required  plastic, 
adhesive,  and  tenacious  qualities.  This  substance  must  be  one  that 
will  partially  dissolve  the  asphaltene  and  form  a  chemical  union  by 
solution  instead  of  a  mechanical  mixture.  The  duty  which  it  has 
to  perform  is  an  important  and  peculiar  one :  if  it  is  a  perfect  sol- 
vent of  the  constituents  of  the  bitumen,  the  adhesive  qualities  will 
bo  destroyed;  if  it  is  an  imperfect  one,  the  asphaltum  will  retain  its 
brittleness. 


46  HIGHWAY    CONSTRUCTION". 

96a.  The  requirements  of  a  suitable  flux  arc  that  it  shall  be  a 
fluid  containing  no  substances  volatile  under  300°  F.,  and  shall 
possess  the  power  to  dissolve  the  asphaltum  without  destroying  or 
lessening  its  adhesive  properties. 

96b.  The  materials  employed  to  give  the  required  qualities  to 
the  hard  asphaltum  are  called  the  "  flux/'  and  those  in  general 
use  are  crude  or  specially  prepared  residuum  oil  obtained  from 
the  distillation  of  petroleum,  and  crude  or  refined  maltha. 

The  process  of  adding  the  flux  is  called  "  oiling  "  or  "  temper- 
ing/' and  is  conducted  as  follows  :  The  refined  asphaltum  is 
melted  and  the  temperature  raised  to  about  300°  F. ;  the  oil  previ- 
ously heated  is  then  pumped  or  in  other  ways  added  to  the 
asphaltum,  in  the  proportion  of  10  to  20  pounds  of  oil  to  100 
pounds  of  refined  asphaltum — the  proportion  of  the  oil  is  varied 
between  the  limits  stated  according  to  its  quality,  the  hardness  of 
the  asphaltum,  and  the  purpose  for  which  the  cement  is  to  be  em- 
ployed. The  mixture  of  residuum  oil  and  asphaltum  is  agitated 
either  by  mechanical  means  or  by  a  blast  of  air  for  several  hours 
or  until  the  material  has  acquired  the  desired  properties.  The 
agitation  must  be  performed  with  great  thoroughness  to  secure  a 
uniform  mixture,  and  must  be  continued  whenever  the  material 
is  in  a  melted  condition,  as  a  certain  amount  of  separation  takes 
place  when  the  melted  cement  stands  at  rest.  It  is  therefore 
customary  to  agitate  it  constantly  when  in  use  as  well  as  during  its 
preparation. 

96c.  The  process  of  "tempering"  when  maltha  is  used  as: 
the  flux  is  practically  the  same  as  outlined  above,  with  the  excep- 
tion that  the  mixing  is  performed  at  a  lower  temperature  and 
entirely  by  mechanical  means,  and  a  separation  of  the  ingredients 
seldom  occurs  when  the  cement  is  standing  at  rest. 

96d.  The  maltha  from  many  localities  is  to  be  had  in  the 
market;  it  is  sold  for  fluxing  purposes  under  various  trade  names, 
among  which  may  be  named  "Alcatraz"  liquid  asphaltum, 
"  Standard  "  liquid  asphalt,  "Utah"  liquid  asphalt,  etc.;  also  arti- 
ficial fluxing  materials  which  are  offered  as  substitutes  for  oil  and 
maltha,  such  as  the  "  Pittsburg  asphaltic  flux,"  etc.  The  analyses 
of  some  of  these  fluxing  agents  are  as  follows  :  . 


MATERIALS   EMPLOYED   IJT   THE   CONSTRUCTION"   OF   PAVEMENTS.     47 

"ALCATRAZ"'  LIQUID  ASPHALT. 

Specific  gravity 1.05 

Bitumen  soluble  in  carbon  disulpbide 98.70  per  cent. 

Bitumen  soluble  in  petroleum  napbtba 89.17    "       " 

Mineral  matter 1.30    "       " 

Organic  non-bituminous  matter ...     trace. 

"UTAH"  LIQUID  ASPHALT  (CRUDE.) 

Specific  gravity 0.9068 

Bitumen  soluble  in  carbon  disulphide 76.15  per  cent. 

Bitumen  soluble  in  ether 64.90   "       " 

Mineral  matter  3.40    "       " 

Organic  non-bituminous  matter ...20.45    "       " 

Loss  at  100° C . ... 24.72   "      " 

"PlTTSBURG"    ASPHALTIC   FLUX. 

Moisture 0.05  per  cent. 

Volatile  oil  212°  F.  to  312°  F 1.60  "  " 

Volatile  oil  about  312' F 89.19  "  " 

Fixed  carbon 8.48  "  " 

Ash 0.68  " 

Bitumen  soluble  in  carbon  disulphide 99.32  "  " 

Bitumen  soluble  in  ether 65.00   " 

97.  The  enduring .  qualities  of  an  asphaltic  cement  depend 
upon  (1)  the  character  of  the  fluxing  agent,  (2)  the  temperature 
at  which  the  asphaltum  has  been  refined  and  the  temperature  at 
which  the  flux  is  added,  (3)  the  degree  of  incorporation  of  the  flux 
with  the  asphaltum,  that  is  whether  the  union  is  a  chemical  or 
mechanical  one. 

97a.  The  diversity  found  in  the  durability  of  pavements  made 
from  cement  in  which  the  flux  is  residuum  of  petroleum  is  con- 
sidered by  many  authorities  to  be  due  primarily  to  the  variable 
character  of  the  residuum.  This  material  is  a  thick  heavy  oil 
varying  considerably  in  composition,  according  to  the  source  of  the 
petroleum  and  method  of  distillation;  its  base  is  paraffine — a  sub- 
stance so  different  from  asphaltum  that  when  the  two  are  brought 
together  the  result  is  a  mixture  partly  mechanical  and  partly 
chemical,  and,  being  of  different  specific  gravities,  they  partly  sepa- 
rate when  allowed  to  stand  for  any  considerable  period  without 
stirring. 

Regarding  the  use  of  petroleum  residuum  as  a  flux  for  asphaltum, 
Mr.  A.  W.  Dow,  Inspector  of  Asphalts  and  Cements,  District  of 


48  HIGHWAY   CONSTRUCTION". 

Columbia,  in  his  report  for  1897  says:  "I  have  made  a  careful 
study  of  this,  and  am  thoroughly  convinced  that  the  use  of  all 
petroleum  residuum  is  injurious,  some  much  more  so  than  others. 
That  it  is  not  adaptable,  either  chemically  or  physically,  to  this  use, 
can  be  readily  seen  by  looking  into  its  properties.  With  a  change  of 
but  a  few  degrees  of  temperature,  it  passes  from  a  liquid  to  a  solid 
state.  On  standing  a  month  or  two  a  hardening  sets  in,  due  either 
to  polymerization  or  slow  crystallization,  which  makes  it  even  more 
susceptible  to  change  in  temperature.  I  am  also  led  to  believe, 
from  various  experiments,  that  many  asphalts  are  not  entirely 
soluble  in  petroleum  residuum,  and  for  that  reason  asphalt  cement 
in  which  it  is  used  is  not  a  chemical,  but  merely  a  mechanical  mix- 
ture or  emulsion  of  the  asphalt  and  the  oil.  From  this  it  can 
readily  be  seen  that  the  undesirable  properties  of  the  petroleum 
residuum  are  imparted  to  the  asphalt  cement  to  a  degree  propor- 
tional to  the  quantity  of  residuum  used." 

97b.  During  the  early  days  of  the  manufacture  of  asphaltic 
cement,  for  paving  purposes,  from  Trinidad  asphalt um  and 
residuum  oil,  the  oil  as  it  came  from  the  refineries  was  poured 
directly  into  the  liquid  asphaltum  without  any  investigation  as  to 
its  quality.  The  results  produced  by  this  method  in  cements 
nominally  prepared  in  exactly  the  same  way  were  very  variable 
and  oftentimes  unsatisfactory.  "With  the  increased  demand  for 
asphaltic  cement  many  improvements  both  in  the  method  of  add- 
ing the  oil  and  in  its  quality  have  been  made.  The  oil  is  now 
subjected  to  careful  examination  to  ascertain  : 

1.  Specific  gravity. 

2.  Flash-point. 

3.  Percentage  volatile  in  a  given  time  at  400°  F. 

4.  Susceptibility  to   changes   in   temperature    as   revealed   by 
changes  in  viscosity. 

5.  Presence  of  crystals  of  paraffine. 

97c.  The  demand  for  heavy  petroleum  oil  or  residuum  for  use 
in  the  manufacture  of  cement  for  paving  purposes  has  become  so 
extensive  that  the  oil-refining  companies  find  it  profitable  to  pro- 
duce an  oil  that  shall  be  nearly  uniform  in  character.  In  pre- 
paring this  oil  the  object  aimed  at  is  (1)  the  removal  of  the  hard 
paraffines,  which  are  very  susceptible  to  changes  of  temperature, 
becoming  soft  under*  the  summer  sun  and  brittle  at  or  below  the 


MATERIALS    EMPLOYED    IN    THE    CONSTRUCTION    OF    PAVEMENTS.    49 

freezing-point  ;  their  presence  imparts  similar  properties  to  the 
asphalt  cement  ;  (2)  to  remove  the  lighter  and  more  volatile  oils  ; 
care  in  their  removal  must  be  exercised:  if  too  large  a  percentage 
is  removed,  the  oil  becomes  heavy  and  thick,  and  too  large  a  pro- 
portion is  required  to  make  a  cement  of  suitable  consistency — there- 
fore there  is  a  limit  to  the  amount  that  can  be  removed. 

97d.  Specifications  for  Petroleum  Residuum. — The  petroleum 
residuum  used  in  the  manufacture  of  asphalt  cement  shall  be  a 
petroleum  from  which  the  lighter  oils  have  been  removed  by  distil- 
lation, without  cracking,  until  the  oil  has  the  following  character- 
istics: 

Specific  gravity  ranging  between  20°  and  23°  Baume. 

Flash-point  (as  taken  in  a  New  York  State  Board  of  Health 
oil-tester),  between  300°  and  425°  F. 

Distillate  at  400°  F.  for  thirty  hours,  less  than  10  per  cent.  The 
distillate  shall  be  made  with  about  50  grams  of  oil  in  a  small  glass 
retort  provided  with  a  thermometer  and  packed  entirely  in  asbestos. 
The  residue  in  the  retort  after  distillation  must  be  fluid  at  75°F., 
and  not  coarsely  crystalline  on  cooling. 

The  quantity  of  residuum  necessary  to  soften  the  asphalt  into  a 
cement  containing  bitumen  whose  penetration  is  80°  on  Bowen's 
scale  shall  not  be  over  33  per  cent  of  the  total  quantity  of  bitumen 
in  the  asphalt. 

The  flowing-point  shall  be  determined  by  cooling  100  cc.  of  oil 
in  a  small  bottle  and  noting  the  temperature  at  which  it  flows 
readily  from  one  end  of  the  bottle  to  the  other. 

98.  Authorities  differ  as  to  the  relative  merits  of  residuum  oil 
and  maltha  as  fluxes  for  asphaltum.  Some  claim  that  they  are 
unsuitable  on  account  of  the  volatile  oils  they  contain,  which  on 
evaporating  leave  the  cement  in  a  porous  or  spongelike  condition, 
which  readily  absorbs  water,  and  is  thus  subject  to  the  destroying 
action  of  frost.  Others  hold  that  if  the  oil  or  maltha  is  heated 
sufficiently  to  drive  off  the  volatile  oils  they  are  deprived  of  their 
solvent  power  and  are  converted  into  substances  so  similar  to  as- 
phaltum that  their  addition  renders  it  more  brittle. 

98a.  The  writer,  from  his  observations,  considers  that  a  more 
enduring  cement  can  be  obtained  by  adding  asphaltum  to  maltha 
and  allowing  it  to  dissolve  therein  at  a  temperature  of  212°  to  220° 
F.,  or  by  submitting  maltha  to  a  process  of  distillation  in  which 


50  HIGHWAY    CONSTRUCTION". 

the  temperature  is  carefully  regulated.  Under  such  a  process 
bitumen  of  any  consistency  from  plastic  to  hard  can  be  produced. 
Either  of  these  methods  would  be  more  satisfactory  and  inore- 
under  control  than  the  present  one  of  transforming  a  compara- 
tively hard  and  brittle  substance  into  a  soft  and  plastic  one. 

98b.  An  examination  of  the  bituminous  limestones  and  sand- 
stones shows  them  to  be  cemented  together,  not  by  hard  bitumen, 
but  by  the  softer  varieties;  and  where  these  formations  have  been 
exposed  to  the  destroying  action  of  the  elements  they  show  no  sign 
of  disintegration,  but  are  solid  and  impervious. 

98c.  Some  of  the  most  enduring  constructions  of  antiquity, 
which  have  withstood  the  ravages  of  time  for  upwards  of  3000 
years,  are  cemented  with  bitumen.  The  bitumen  which  the  an- 
cients used  was  not  the  hard  brittle  variety  we  employ,  but  the 
soft  plastic  maltha,  used  in  its  natural  condition  as  it  oozed  out  of 
the  springs. 

99.  Asphaltic  Paving  Materials. — All  asphaltic  or  bituminous 
pavements  are  composed  of  two  essential  parts,  namely,  the  ce- 
menting material  (matrix)  and  the  resisting  material  (aggregate). 
Each  has  a  distinct  function  to  perform:  the  first  furnishes  and 
preserves  the  coherency  of  the  mass;  the  second  resists  the  wear 
of  the  traffic. 

99a.  Two  classes  of  asphaltic  paving  compounds  are  in  use, 
namely,  natural  and  artificial.  The  natural  variety  is  composed 
of  either  limestone  or  sandstone  naturally  cemented  by  bitumen. 
To  this  class  belong  the  bituminous  limestones  of  Europe,  Texas, 
Utah,  etc.,  and  the  bituminous  sandstones  of  California,  Kentucky, 
Texas,  Indian  Territory,  etc.  The  artificial  consists  of  mixtures  of 
asphaltic  cement  manufactured,  as  described  in  Art.  96,  with  sand 
and  stone-dust.  To  this  class  belong  the  pavements  made  from 
Trinidad,  Bermudez,  Cuban,  and  similar  asphaltums.  For  the 
artificial  variety  most  of  the  hard  bitumens  are,  when  properly 
prepared,  equally  suitable.  For  the  aggregate  the  most  suitable 
materials  are  stone  dust  from  the  harder  rocks,  such  as  granite, 
trap,  etc.,  and  sharp  angular  sand.  These  materials  should  be 
entirely  free  from  loam  and  vegetable  impurities.  The  strength 
and  enduring  qualities  of  the  mixture  will  depend  upon  the? 


MATERIALS    EMPLOYED    IN"    THE    CONSTRUCTION    OF    PAVEMENTS.     5t 

quality,  strength,  and  proportion  of  each  ingredient,  as  well  as 
upon  the  cohesion  of  the  matrix  and  its  adhesion  to  the  aggregate. 

99b.  Bituminous  Limestone  consists  of  carbonate  of  lime  natu- 
rally cemented  with  bitumen  in  proportions  varying  from  80  to  93 
per  cent  of  carbonate  of  lime  and  from  7  to  20  per  cent  of  bitumen. 
Its  color  when  freshly  broken  is  a  dark  (almost  black)  chocolate- 
brown,  the  darker  color  being  due  to  a  larger  percentage  of  bitu- 
men. At  a  temperature  of  from  55°  to  70°  F.  the  material  is  hard 
and  sonorous  and  breaks  easily  with  an  irregular  fracture;  at  tem- 
peratures between  70°  and  140°  F.  it  softens,  passing  with  the  rise 
in  temperature  through  various  degrees  of  plasticity,  until,  at  be- 
tween 140°  and  160°  F.,  it  begins  to  crumble,  at  212°  F.  it  com- 
mences to  melt,  and  at  280°  F.  it  is  completely  disintegrated.  Its 
specific  gravity  is  about  2.235. 

99c.  Bituminous  limestone  is  the  material  employed  for  paving 
purposes  throughout  Europe.  It  is  obtained  principally  from  de- 
posits at  Val-de-Travers,  canton  of  Neufchatel,  Switzerland;  at 
Seyssel,  in  the  department  of  Ain,  France;  at  Kagusa,  Sicily;  at 
Limmer,  near  Hanover;  and  at  Vorwohle,  Germany. 

99d.  The  constituents  of  the  more  important  of  these  deposits 
are  given  in  Table  XV. 

99e.  Bituminous  limestone  is  found  in  several  parts  of  the 
United  States.  Two  of  these  deposits  are  at  present  being  worked, 
one  in  Texas,  the  material  from  which  is  called  "  lithocarbon," 
and  one  on  the  Wasatch  Indian  Eeservation.  These  deposits  con- 
tain from  10  to  30  per  cent  of  bitumen. 

99f.  The  bituminous  limestones  which  contain  about  10  per 
cent  of  bitumen  are  used  for  paving  in  their  natural  condition, 
being  simply  reduced  to  powder,  heated  until  thoroughly  softened, 
then  spread  while  hot  upon  the  foundation  and  tamped  and  rammed 
until  compacted. 


HIGHWAY   CONSTRUCTION. 


TABLE   XV. 
ANALYSIS  OF  EUROPEAN  BITUMINOUS  ROCKS.* 


Constituents. 

Val 
de 

Travers. 

Seyssel. 

Lobsan. 

Sicil- 
ian. 

Mae- 
stu. 

Forens. 

Water  and  matter  vol.  at  212°  F.f 

Pet- 
cent. 

0.50 
10  10 

Per 
cent. 

1.90 
8  00 

Pei- 
cent. 

3.40 

11.90:}: 

Per 

cent. 

0.80 

8.85 

Pei- 
cent. 

0.40 

8  80 

Per 

cent. 

0.25 
2  25 

87.95 

89.55 

69.00 

87.50 

9.15 

97  00 

3  05 

0  60 

57  40 

Aluminum  and  peroxide  of  iron 
Sulphur  

0.25 

0.15 

5.70§ 
5  00 

0.90 

4.35 

0.15 

Carbonate  of  magnesia  

0.30 

0.10 

0.30 

0.95 

8.10 

0  20 

Different  materials  insol  in  acids 

0  45 

0  10 

11  35 

0  05 

0.45 

0.20 

1  65 

0.40 

0  45 

0  10 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

*  Laboratoire  de  1'Ecole  des  Pouts  et  Chaussees.     M.  Leon  Malo. 

\  The  water  given  above  depends  on  the  dryuess  of  the  sample  at  the  time 
of  analysis,  the  figures  not  being  of  importance  in  the  result. 

\  This  quantity  appeared  to  contain  a  certain  proportion  of  oil,  which  was 
mixed  with  the  bitumen  and  was  not  exactly  determined. 

§  This  comprises  4.45  per  cent  of  iron  combined  with  sulphur. 

ANALYSIS  OP  LITHOCARBON,  UVALDE  COUNTY,  TEXAS. 

Water 00.27 

Asphalt 13. 68 

Sulphur trace. 

Iron  pyrites trace. 

Alumina '. 0.60 

Magnesia 0.31 

Carbonate  of  lime 82.06 

Silica..  3.08 


100.00 

Bituminous  Sandstones  are  composed  of  sandstone  rock 
impregnated  with  bitumen  in  amounts  varying  from  a  trace  to  70 
per  cent.  They  are  found  both  in  Europe  and  America.  In  Europe 
they  are  chiefly  used  for  the  production  of  pure  bitumen,  which  is 
extracted  by  boiling  or  macerating  them  with  water.  In  the 
United  States  extensive  deposits  are  found  in  the  Western  States, 


MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION    OF   PAYEMENTS.    53 

and  since  1880  they  have  been  gradually  coming  into  use  as  a 
paving  material,  and  now  upwards  of  a  hundred  and  fifty  miles  of 
streets  in  Western  cities  are  paved  with  them.  They  are  prepared 
for  use  as  a  paving  material  by  crushing  to  powder,  which  is  heated 
to  about  250°  F.,  or  until  it  becomes  plastic,  then  spread  upon  the 
street  and  compressed  by  rolling;  sometimes  sand  or  gravel  is 
added,  and  it  is  stated  that  a  mixture  of  about  80  per  cent  of  gravel 
makes  a  durable  pavement.  Good  results  have  been  obtained  by 
mixing  from  10  to  50  per  cent  of  bituminous  limestone,  such  as 
that  from  Vorwhole,  Germany.  This  rock  contains  from  7  to  10 
per  cent  of  hard  asphaltum  without  any  oils,  and  imparts  to  the  more 
friable  sandstones,  having  the  asphaltum  in  a  different  condition, 
the  tenacity  and  hardness  which  they  lack  in  the  natural  condition. 
Kentucky  Bituminous  Sandstone. — The  bituminous  sandstone 
found  in  Breckinridge  County,  Ky.,  has  been  used  in  several  cities, 
including  Louisville,  Brooklyn,  Buffalo,  etc.  It  is  composed  of  fine 
white  sand  and  from  8  to  12  per  cent  of  bitumen.  An  analysis  of 
the  sandstone  showed  that  it  contains  96.88  per  cent  of  silica,  0.81 
of  sesquioxide  of  iron,  0.46  of  alumina,  0.34  of  lime,  0.2  of  mag- 
nesia, 0.81  of  soda,  0.2  of  potash,  and  0.25  of  combined  water  and  loss. 
Eecent  specifications  for  the  preparation  of  this  material  re- 
quire that  the  wearing  surface  of  the  pavement  is  to  be  composed 
of  80  to  70  per  cent  of  the  Kentucky  rock  and  20  to  30  per  cent  of 
Vorwhole  (German)  bituminous  limestone.  These  rocks  to  be 
pulverized  and  the  powder  of  each  mixed  in  the  mills  and  then 
screened.  The  mixture  to  be  heated  to  a  temperature  of  from  150° 
to  250°  F.,  and  to  reach  the  street  at  not  less  than  the  former  tem- 
perature, spread  in  one  layer,  compressed  with  hot  rollers  and 
tampers  to  a  thickness  of  two  inches. 

Utah  Bituminous  Calcareous  Sandstone. — This  sandstone  has- 
been  used  for  paving  with  varying  results.  It  contains  about  11 
per  cent  of  bitumen  and  89  per  cent  mineral  matter,  which  con- 
sists of 

Silica  and  insoluble  silicates 68.00 

Ferric  oxide !-16 

Aluminum  oxide 2-30 

Calcium  carbonate 26.63 

Magnesium  carbonate,  alkali,  and  undetermined  matter 1.91 

100.00 


54  HIGHWAY   CONSTRUCTION. 

100.  Trinidad  Asphaltum. — The  deposits  of  asphaltum  in  the 
island  of  Trinidad,  W.  I.,  have  been  the  main  source  of  supply  for 
the  asphaltum  used  in  street-paving  in  the  United  States.  Three 
kinds  are  found  there,  which  have  been  named,  according  to 
the  source,  lake  pitch,  land  or  overflow  pitch,  and  iron  pifch, 
The  first  and  most  valuable  kind  is  obtained  from  the  so-called 
Pitch-lake;  this  lake  or  deposit  is  situated  about  2  miles  from 
the  seashore  of  the  island  at  an  elevation  of  138  feet,  and  has  an 
area  of  about  115  acres  and  is  of  unknown  depth.  It  is  quite  cir- 
cular in  shape,  and  is  supposed  to  occupy  the  crater  of  an  extinct 
mud  volcano,  The  surface  is  not  flat  and  even,  but  is  formed  of 
irregular  oval-shaped  domes,  resembling  large  mushrooms,  separated 
by  narrow  and  shallow  channels  and  pools  of  water;  with  ihe 
exception  of  a  small  space  in  the  centre  the  surface  is  sufficiently 
hard  to  support  the  weight  of  animals  and  loaded  carts.  -The 
small  space  in  the  centre  is  called  the  "  boiling  spring."  Here  soft 
pitch  still  wells  up,  but  soon  becomes  hard.  The  asphaltum  is 
easily  excavated  with  picks,  and  in  the  early  days  of  the  industry 
was  loaded  into  two-wheeled  carts,  hauled  by  mules  to  the  shore, 
and  there  dumped  into  piles,  from  which  it  was  carried  in  baskets 
by  coolies  wading  through  the  surf  to  lighters  and  from  the  lighters 
loaded  into  sail  ing  vessels.  Eecently  the  concessionaires  of  the  lake 
have  built  a  tramway  and  pier  by  which  the  material  is  easily  con- 
veyed and  quickly  loaded  into  the  vessels  lying  at  the  pier. 

lOOa.  The  term  land  or  overflow  pitch  is  applied  to  the 
deposits  of  asphaltum  found  outside  of  the  lake.  These  deposits 
form  extensive  beds  of  variable  thickness,  and  are  covered  with 
from  a  few  to  several  feet  of  earth;  they  are  considered  by  some 
authorities  to  be  formed  from  pitch  which  has  overflowed  from  the 
lake,  by  others  to  be  of  entirely  different  origin.  The  name  cheese 
pitch  is  given  to  such  portions  of  the  land  pitch  as  more  nearly 
resemble  that  obtained  from  the  lake. 

lOOb.  The  term  iron  pitch  is  used  to  designate  large  and  isolated 
masses  of  extremely  hard  asphaltum  found  both  within  and  with- 
out the  borders  of  the  lake.  It  is  supposed  to  have  been  formed 
by  the  action  of  heat  caused  by  forest  fires  which,  sweeping  over 
the  softer  pitch,  removed  its  more  volatile  constituents. 

lOOc.  The  name  epuree  is  given  to  asphaltum  refined  on  the 


MATERIALS   EMPLOYED    Itf   THE    CONSTRUCTION    OF    PAVEMENTS.     55 


island    of   Trinidad.     The   process   is   conducted  in  a  very  crude 
manner  in  large,  open,  cast  iron  sugar  boilers. 

lOOd.  The  Characteristics  of  Crude  Trinidad  Asphaltum,  both 
lake  and  land  are  as  follows:  It  is  composed  of  bitumen  mixed 
with  fine  sand,  clay,  and  vegetable  matter.  Its  specific  gravity 
varies  according  to  the  impurities  present,  but  is  usually  about 
1.28.  Its  color  when  freshly  excavated  is  a  brown,  which  changes 
to  black  on  exposure  to  the  atmosphere.  When  freshly  broken, 
it  emits  the  usual  bituminous  odor.  It  is  porous,  containing 
gas-cavities,  and  in  consistency  it  resembles  cheese.  If  left  long 
enough  in  the  sun,  the  surface  will  soften  and  melt  and  will  finally 
flow  into  a  more  or  less  compact  mass.  The  average  composition 
of  both  the  land  and  lake  varieties  is  shown  by  the  following 
analyses : 

TABLE  XVI. 

AVERAGE  COMPOSITION  OF  TRINIDAD  ASPHALTUM. 


Constituents. 

La 

':a. 

Land. 

Hard. 

Soft. 

Water  

Per  cent. 

27.85 

Per  cent. 
34.10 

Per  cent. 
2Q.62 

Inorganic  matter       .           

26.38 

25.05 

27.57 

Organic  non-bituminous  matter.  .  . 

7.63 
38.14 

6.35 
34.50 

8.05 
37.76 

100.00 

100.00 

100.00 

When  the  analyses  are  calculated 
to  a  basis  of  dry  substances, 
the  composition  is  inorganic 
matter  

36.56 

38.00 

37.74 

Organic  mutter  not  bitumen.  .  .  . 

10.57 

9.64 

10.68 

Bitumen  

52.87 

52.36 

51.58 

100.00 

100.00 

100.00 

The  substances  volatilize      in     1C 
hours  at  400°  F. 
'            "          soften  at            .  .  . 

3.66 
190°  F. 

12.24 
170°  F. 

0  86  to  1.37 
200°  to  2.50°  F. 

"            «          flow  at     

200°  F. 

185°  F. 

210°  to  328°  F. 

lOOe.  Refined  Trinidad  Asphatum.— The   crude   asphaltum   is 
refined  or  purified  by  melting  it  in  iron  kettles  or  stills  by  the  ap- 


56  HIGHWAY    CONSTRUCTION. 

plication  of  indirect  heat.  In  the  earlier  refineries  upright  cylin- 
drical kettles  holding  about  ten  tons  were  used;  the  heat  was 
obtained  from  a  coal  fire,  the  kettles  being  protected  from  its 
direct  action  by  a  brick  arch.  In  this  form  of  still  the  refining 
process  occupied  from  one  hundred  and  twenty  to  one  hundred 
and  forty  hours,  and,  as  the  plant  became  deteriorated,  much 
longer;  sediment  collected  on  the  bottom,  causing  much  waste  of 
fuel,  coking  of  the  asphaltum,  and  the  burning  out  of  the  still 
itself.  In  consequence  of  these  defects  their  use  is  practically 
abandoned  and  in  their  place  horizontal  boilers  have  been  adopted. 
In  their  most  approved  form  these  boilers  or  stills  consist  of  a 
boiler  about  twenty  feet  long  and  ten  feet  in  diameter  furnished 
with  two  longitudinal  flues  eighteen  inches  in  diameter  placed  four 
feet  from  the  bottom  and  four  feet  between  centres.  These  stills 
are  placed  in  brickwork  surrounded  with  loam  to  prevent  radia- 
tion, and  are  provided  with  flues  so  arranged  that  the  direct  heat 
from  the  fire  passes  first  along  one  side,  then  back  along  the  other, 
repeating  this  at  a  higher  level,  then  through  one  flue  in  the  still 
and  back  through  the  other,  and  finally  under  the  bottom.  In 
this  way  overheating  on  the  bottom  is  prevented  and  better  results 
are  obtained  in  evaporating  the  water  from  the  upper  layers  of 
crude  material.  These  stills  hold  about  thirty  tons  of  crude  ma- 
terialj  and  the  time  of  refining  is  much  reduced.  After  some  years 
practice  with  the  above-described  method  agitation  of  the  asphal- 
tum with  a  current  of  air  during  the  refining  process  was  intro- 
duced, with  the  object  of  further  reducing  the  time  required 
and  the  possibility  of  injury  to  the  asphaltum. 

Kecently  a  departure  has  been  made  from  this  last-described 
method ;  it  consists  in  the  use  of  steam-heat  in  place  of  coal-fire 
heat.  The  objects  aimed  at  are  a  reduction  in  time  and  prevention 
of  the  injury  by  coking  or  burning  of  the  asphaltum,  which  fre- 
quently occurred  when  refining  with  direct  heat.  In  this  later 
process  instead  of  large  cylindrical  boilers  or  stills  smaller  rectangu- 
lar kettles  are  used,  holding  about  twenty-five  tons  ;  these  are  fur- 
nished  with  gangs  of  pipe  for  the  circulation  of  steam  at  a  press- 
ure of  about  100  pounds  per  square  inch;  agitation  is  produced 
by  jets  of  dry  steam  or  air.  By  this  method  a  charge  is  refined  in 
about  twelve  hours  and  the  product  is  very  uniform  in  quality. 


MATERIALS    EMPLOYED    IN    THE    CONSTRUCTION    OF    PAVEMENTS.     57 


lOOf.  Irrespective  of  the  method  adopted  for  heating,  the  proc- 
ess of  refining  proceeds  as  follows  :  During  the  heating  the  water 
and  lighter  oils  are  evaporated,  the  asphaltum  is  liquefied,  the 
vegetable  matter  rises  to  the  surface  and  is  skimmed  off,  the 
earthy  and  silicious  matters  settle  to  the  bottom,  and  the  liquid 
asphaltum  is  drawn  off  into  old  cement-  or  flour-barrels. 

lOOg.  When  the  asphaltum  is  refined  without  agitation,  the 
residue  remaining  in  the  still  forms  a  considerable  percentage  of 
the  crude  material,  frequently  amounting  to  12  per  cent,  and  it 
was  at  one  time  considered  that  the  greater  the  amount  of  this 
residue  the  better  the  quality  of  the  refined  asphaltum  ;  but  since 
agitation  has  been  adopted  the  greater  part  of  the  earthy  and 
silicious  matters  are  retained  in  suspension  and  it  has  come  to 
be  considered  just  as  desirable  for  a  part  of  the  surface  mixture 
as  the  sand  which  is  subsequently  added.  The  refined  asphaltum, 
if  for  local  use,  is  generally  converted  into  cement  in  the  same 
still  in  which  it  was  refined.  , 

lOOh,  In  the  earlier  part  of  the  refining  process  the  water  con- 
tained in  the  crude  material  is  liberated  and  forms  in  pools  on  the 
surface  ;  this  water  is  of  a  distinct  saline  and  thermal  character, 
containing  a  large  amount  of  salts  in  solution,  which  probably 
explains  the  efflorescence  seen  upon  the  crude  asphaltum  and  which 
is  frequently  attributed  to  sea  salt. 

lOOi.  The  principal  salts  in  solution  are,  in  the  order  of  their 
amount,  sodic  chloride  and  sulphate,  ammonic,  potassic,  and  fer- 
rous sulphates,  borates,  iodides,  etc. 

lOOj.  The  distillate  from  the  stills  is  strongly  acid,  and  free 
hydrochloric,  sulphuric,  and  hydrosulphuric  acids  and  other  sul- 
phur compounds  have  been  determined  in  it. 

100k.  The  steam  which  is  formed  in  the  refining  of  the  crude 
asphaltum  at  first  contains  much  hydrogen  sulphide,  which  blackens 
all  the  white-lead  paint  in  the  vicinity  of  the  refinery.  This,  under 
favorable  conditions  of  heat  and  evaporation,  at  times  changes  to 
sulphurous  anhydride,  which  again  bleaches  out  the  white  paint. 
The  condensed  steam  shows  a  strongly  acid  reaction.  In  the  pres- 
ence of  one  another  the  hydrocarbons  and  the  thermal  water  at 
high  temperature  evidently  produce  complicated  reactions. 

1001.  The  residue  from  the  bottom  of  the  still  consists  of  some 
clay  mixed  with  silica  in  the  form  of  minute  fragments  of  quartz 


58 


HIGHWAY   CONSTRUCTION. 


and  some  of  the  salts  contained  in  the  water.     An  analysis  showed 
it  to  consist  of: 

Clay,  silica,  and  silicates  insoluble  in  acid 87.67  p.c. 

Soluble  salts,  alumina,  iron,  lime,  etc 12.33  p.c. 

100.00  P.  c. 

Of  the  insoluble  portion  about  95  per  cent  is  silica,  and  fre- 
quently the  lime  is  absent. 

100m.  The  organic  matter  not  .bituminous  posseses  no  dis- 
tinctive characteristics;  it  occurs  as  an  impalpable  powder  without 
any  signs  of  organization. 

lOOn.  The  Characteristics  of  Refined  Trinidad  Asphaltum  are 
as  follows : 

AVERAGE  COMPOSITION  OF  REFINED  TRINIDAD  ASPHALTUM. 


Lake. 

Land. 

Specific  gravity  at  77°  F  ,  .  .  . 

1.38 

1.42 

Per  cent. 
56.29 

Per  cent. 
53.75 

Orsranic  matter  not  bituminous               .   . 

8  05 

8  01 

35  66 

38  24 

100.00 

100.00 

Bitumen  soluble  in  petroleum  naphtha  

41  43 

35  22 

73  60 

65  32 

Softens  at        .               •             .  .         .... 

190°  F 

210°  F 

Flows  at  

205°  F 

')30°  F 

The  color  is  black  with  a  homogeneous  appearance.  At  a  tem- 
perature of  about  70°  F.  it  is  very  brittle  and  breaks  with  a  con- 
choidal  fracture;  it  burns  with  a  yellowish-white  flame,  and  in 
burning  emits  an  empyreumatic  odor,  and  possesses  little  cementi- 
tious  quality;  to  give  it  the  required  plasticity  and  tenacity  it  is 
mixed  while  liquid  with  from  16  to  21  pounds  of  residuum  oil  to 
100  pounds  of  asphaltum  in  the  manner  described  in  Art.  96. 

lOOo.  The  product  resulting  from  the  combination  is  called 
asphalt  paving -cement;  its  consistency  should  be  such  that,  at  a 
temperature  of  from  70°  to  80°  F.,  it  can  be  easily  indented  with 
the  fingers  and  on  slight  warming  be  drawn  out  in  strings  or 
threads. 


MATERIALS   EMPLOYED   IN"   THE   CONSTRUCTION   OF   PAVEMENTS.     59 

lOOp.  The  relative  quality  of  Trinidad  lake  and  land  asphaltum 
for  paving  has  been  the  subject  of  much  discussion  and  investiga- 
tion, but  without  any  positive  decision  being  reached. 

lOOq.  That  there  is  no  essential  difference  in  the  chemical 
oomposition  will  be  seen  by  an  examination  of  the  analyses  given 
in  Table  XV«  and  Art.  lOOn. 

lOOr.  The  difference  between  the  two  varieties  consists  not  in 
xi  material  variation  in  the  proportion  of  the  constituents,  but  in  a 
Tariation  or  change  in  the  character  of  the  bitumen.  This  change 
is  due  to  evaporation,  volatilization  and  oxidation  of  the  light  and 
Tolatile  oils,  thus  hardening  it  and  necessitating  a  larger  amount 
of  flux  to  soften  the  land  asphaltum  for  use  as  a  cement.  This 
larger  percentage  of  flux  is  by  some  authorities  said  to  reduce  the 
-enduring  qualities  of  the  cement;  others  claim  that  no  amount  of 
flux  will  restore  the  lost  qualities.  Hence  the  object  in  selecting 
lake  asphaltum,  in  which  a  large  percentage  of  the  natural  oils 
still  remains,  and  rejecting  the  land  asphaltum  which,  has  lost 
these  oils  in  a  large  degree. 

100s.  In  Europe  crude  Trinidad  asphaltum  is  used  for  mixing 
with  the  bituminous  limestones  in  the  manufacture  of  asphalt 
mastic;  for  this  purpose  it  is  refined  as  follows:  The  crude  as- 
phaltum is  melted  in  suitable  vessels  and  to  it  is  added  the  residue 
or  by-products  from  the  petroleum  distilleries  and  paraffine  factories 
in  the  proportion  of  about  2  parts  of  residue  to  3  parts  of  asphaltum  ; 
the  mixture  is  boiled  for  8  or  9  hours,  during  which  time  the  earthy 
and  mineral  substances  in  the  asphaltum  settle  to  the  bottom;  the 
liquid  asphaltum  is  then  drawn  off  and  is  ready  for  use.  This 
preparation  is  known  in  England  as  refined  bitumen;  in  France  as 
bitume  rafine,  bitume  compose,  and  goudron  compose;  in  Germany  as 
goudron. 

101.  Bermudez  Asphalt. — This  is  the  name  given  to  the  asphaltum 
obtained  from  a  lake  or  deposit  situated  in  the  state  of  Bermudez, 
Venezuela.  This  deposit  is  said  to  have  an  area  of  over  1000  acres. 
It  is  situated  about  60  miles  from  the  coast  up  the  San  Juan 
Eiver,  and  about  51  miles  distant  from  it;  a  narrow-gauge  steam 
railroad  connects  the  deposit  with  the  shipping  point,  and  vessels 
drawing  18  feet  of  water  can  be  loaded  directly  from  the  cars. 

The  crude  asphaltum  is  of  the  same  variety  as  the  Trinidad, 


GO  HIGHWAY    CONSTRUCTION. 

namely,  bitumen  mixed  with  sand,  clay,  and  vegetable  matter;  its 
average  specific  gravity  is  1.09,  and  its  average  composition  is  as 
follows: 

Per  cent. 

Bitumen 93 . 54 

Mineral  matter 2.16 

Organic  matter  not  bituminous 1.15 

Water 3.15 

100.00 

Petrolene 77.90 

Asphaltene 21 . 08 

Retiue..  1.02 


100.00 

The  refining  process  is  practically  similar  to  that  desbribed 
under  Trinidad  asphaltum,  but  is  much  more  rapid,  owing  to  the 
small  amount  of  water  and  mineral  matter  present.  In  manufac- 
turing the  cement  it  requires  much  less  petroleum  residuum  than 
the  Trinidad  on  account  of  the  large  amount  of  oil  that  it  contains; 
it  melts  at  a  lower  temperature  than  the  Trinidad,  and  the  follow- 
ing are  some  of  its  characteristics:  At  60°  F.  compressible;  at 
70°  F.  viscous  and  malleable;  at  100°  F.  flowing,  and  can  be 
stretched  in  hairlike  threads;  at  189 °F.  melts;  at  400°  F.  gives  no 
flash.  (See  also  Art.  2650.) 

102.  California  Asphaltum. — Asphaltum  is  produced  in  Cali- 
fornia by  refining  the  bitumen  from  the  extensive  sandstone  and 
other  deposits  which  are  found  in  various  parts  of  the  State.  The 
characteristics  of  both  the  crude  and  refined  asphaltum  from  some 
of  the  more  important  deposits  are  shown  by  the  following  an- 
alysis : 

ANALYSIS  OF  ASPHALTUM  PROM  BAKERSFIELD,  CAL. 

Crude.  Refined. 

Specific  gravity 1.132  1.240 

Softensat 180°  F.  150°  F. 

Flows  at 220°  F.  180°  F. 

Inorganic  matter 9.57  p.  c.  9. 77  p.  c. 

Bitumen  soluble  in  CSa 85.49  p.  c.  90. 16  p.  c. 

Bitumen  soluble  in  ether 69.98  p.  c.  86.45  p.  c. 

Percentage  of  total  bitumen  soluble  in 

ether 81.85p.c.  95.88  p.  c. 


MATERIALS    EMPLOYED    IN   THE    CONSTRUCTION   OF    PAVEMENTS.     Gl 

ANALYSIS  OP  ASPHALTUM  FROM  ASPHALTO,  CAL. 

Crude.  Refined. 

Moisture 6.51  p.  c.  0.42  p.  c. 

Bitumen  soluble  in  chloroform 84.79  p.  c.  93.27  p.  c. 

Organic  matter  (not  bitumen) trace  0.54  p.  c. 

Inorganic  matter  consisting  of  infuso- 
rial earth  with  traces  of  iron 8.70  p.  c.  5.77  p.  c. 

Petrolene  soluble  in  acetone 67 . 50  p.  c.  71 . 27  p.  c. 

Asphalteue  insoluble  in  acetone 32.50  p.  c.  28.73  p.  c. 

Combined  sulphur  (chemically  held  in 
the  bitumen) 0.73  p.  c. 

ANALYSIS  OP  ASPHALTUM  PROM  SANTA  BARBARA  Co.,  CAL. 

Crude.  Refined. 

Specific  gravity 1 .250 

Organic  non-bituminous  matter 1.10  p.  c. 

Inorganic  matter  consisting  of  finely 

divided  quartz  with  oxide  of  iron 

and  alumina.    ...    39. 75  p.  c. 

Bitumen  soluble  in  CS2 59. 15  p.  c. 

Bitumen  soluble  in  petroleum  naphtha 

(petroleue) 42.50  p.  c. 

Asphaltene 7. 35  p.  c. 

ANALYSIS  OP  ASPHALTUM  FROM  KERN  Co.,  CAL. 

Bitumen  soluble  in  CS2 78.90  p.  c. 

Mineral  substances — sand,  clay,  and  silica 9.40  p.  c. 

Coky  and  volatile  matter 4. 53  p.  c. 

Water  and  loss 7. 17  p.  c. 

ANALYSIS  OF  BITUMINOUS  SANDSTONE  PROM  VENTURA  Co:,  CAL. 

Bitumen 24 . 00  p.  c. 

Silica 64. 00  p.  c. 

Oxide  of  iron  > 

Calcium  carbonate  f 12 . 00  p.  c. 

Cements  for  paving  and  other  purposes  are  manufactured  from 
the  refined  asphaltum  described  above  by  the  admixture  of  maltha; 
the  two  substances  are  combined  at  a  very  low  temperature,  the 
heat  being  applied  indirectly,  and  the  mixing  is  performed  mechan- 
ically; the  degree  of  softness  can  be  made  to  suit  any  requirement. 

102a.  Buena  Vista  Asphalt. — The  asphaltic  paving  cement -sold 
under  this  name  is  prepared  from  a  liquid  asphaltum  obtained 
from  California  and  a  hard  asphaltum  from  Utah,  and  contains  no 


62  .        HIGHWAY    CONSTRUCTION. 

residuum  of  petroleum.     The  following  analysis  shows  its  compo- 
sition : 

Bitumen  soluble  in  carbon  disulphide 99. 12  to  99.33 

Earthy  and  insoluble  organic  matter 88  to      .67 

103.  Asphalt  Mastic. — In  Europe  mastic  is  made  from  a 
mixture  of  bituminous  limestone  and  refined  asphaltum  (usually 
Trinidad).  The  bituminous  limestone  is  reduced  to  powder  and 
mixed  with  about  8  per  cent  of  refined  asphaltum,  then 
melted  and  thoroughly  mixed.  The  hot  composition  is  run  into 
moulds  of  various  shapes,  usually  round  or  hexagonal,  and  of  such 
dimensions  as  will  give  a  cake  or  block  weighing  about  56  pounds  ;. 
these  blocks  usually  have  the  name  of  the  source  or  factory  moulded 
on  them. 

The  mastic  is  prepared  for  use  by  breaking  the  cakes  into  small 
pieces,  and  heating  it  with  the  addition  of  about  5  per  cent  of  re- 
fined asphaltum.  The  mass  is  constantly  stirred  and  when  soft, 
sand  and  fine  gravel  are  added  and  thoroughly  incorporated  by 
stirring  for  about  two  hours  at  a  temperature  of  about  300°  F.,  when. 
it  is  ready  for  use. 

Asphalt  mastic  is  also  prepared  from  bituminous  sandstones 
and  maltha  or  refined  asphaltum,  and  from  asphalt  paving-cement. 
The  principal  use  of  mastic  is  for  sidewalks  and  floors.  In  Europe 
it  is  called  Asplialte  conU  in  distinction  from  the  compressed 
bituminous  limestone,  which  is  called  Asplialte  comprime.  (See 
also  Art.  266,  et  seq.,  and  Art.  778,  et  seq.) 

103a.  Analysis  and  Tests  of  Asphaltum. — The  tests  employed 
to  determine  the  relative  merits  of  asphaltum  and  asphaltic  cements 
comprise  both  chemical  and  physical  investigations. 

The  chemical  examination  of  the  crude  material  involves  the 
following  determinations: 

Specific  gravity. 
Percentage  of  moisture. 

"  ft   matter  soluble  in  turpentine. 

"      "   carbon  bisulphide. 
"          "        "  "      "   alcohol. 

"  "        "  "      "  ether. 

"  "        "      volatile  in  10  hours  at  400°  F. 

•'  "   sulphuretted  hydrogen  evolved  at  400°  F. 

"  "   non-bituminous  organic  matter. 

"          "  mineral  constituents. 


MATERIALS    EMPLOYED    IS    THE    CO^ttTRUCTKW    OF    PAVEMENTS.     63 

Softening-point  of  the  bitumen. 

Flowing-point     "     "  " 

Stability  of  the  bitumen  at  high  temperature. 

Action  of  water  and  ammonia  on  the  bitumen. 

Change  in  bitumen  due  to  aging. 

Susceptibility  of  bitumen  due  to  change  with  variations  in 
temperature. 

The  examination  of  the  physical  properties  (mechanical  tests) 
involve  the  following  determinations: 

(1)  The   refining   of   the  crude   material  and   making   of  an 
asphaltic  cement. 

(2)  Determining  the  viscosity  or  softness  of  the  cement. 
(This     investigation    is   commonly  called  the   "penetration" 

test;  its  purpose  is  to  ascertain  whether  the  cement  is  of  the 
proper  degree  of  softness  to  produce  a  good  pavement.  The 
degree  of  softness  or  viscosity  depends  partly  upon  the  quality  of 
the  asphaltum  and  partly  upon  the  character  and  proportion  of  the 
flux;  it  also  increases  and  diminishes  as  the  temperature  is  raised 
or  lowered;  hence  great  care  is  required  when  examining  several 
samples  of  the  same  cement  or  comparing  samples  of  different 
cements  to  have  them  all  at  the  same  temperature.  Experience 
shows  that  to  secure  the  best  results  the  viscosity  or  softness  of  the 
cement  must  differ  in  different  localities  according  to  the  climate, 
and  also  according  to  the  character  of  the  sand  and  dust  used.) 

(3)  Making  a  paving  mixture  and  testing  it  for  tensile  and 
crushing  strength. 

Amount  of  Bitumen. — The  amount  of  bitumen  contained  in 
the  crude  material  is  ascertained  by  extracting  it  with  a  solvent 
(carbon  disulphide  is  the  most  commonly  used).  This  extraction 
may  be  made  in  numerous  ways.  The  method  requiring  the  least 
experience  and  giving  the  least  trouble  is  by  extracting  in  large 
test-tubes  or  cylinders,  and  decanting  off  the  solvent  containing 
the  dissolved  bitumen  from  the  insoluble  portions. 

The  method  of  procedure  is  as  follows:  The  sample  of  asphal- 
tum is  spread  in  a  thin  layer  in  a  suitable  dish  (nickel  or  iron), 
and  kept  at  a  temperature  of  225°  F.,  until  it  practically  stops 
losing  weight.  The  greater  part,  and  in  some  cases  all  the  water 
and  some  light  oils  are  expelled  in  this  way.  From  2  to  10  grams 


HIGHWAY    CONSTRUCTION. 


(depending  on  its  richness  in  bitumen)  of  the  sample  is  weighed  in 
.a  large  sized  test-tube  (8  inches  long  by  1  inch  diameter),  the  tare 
of  which  has  been  previously  ascertained.  The  tube  containing 
the  sample  is  then  filled  to  within  1|  inches  of  the  top  with  carbon 
•disulphide  and  allowed  to  stand  for  a  few  minutes.  Then  the 
tube  is  tightly  corked  with  a  good  sound  cork.  It  is  then  shaken 
vigorously  until  no  material  can  be  seen  adhering  to  the  bottom. 
Care  should  be  taken  while  shaking  to  keep  one  finger  on  the  cork 
to  prevent  its  being  blown  out.  The  tube  should  then  be  put 
away  in  an  upright  position  and  not  disturbed  in  the  slightest  way 
for  two  days,  after  which  the  solvent  is  decanted  off  into  a  small 
hottle.  As  much  of  the  solvent  should  be  poured  off  as  is  possible 
without  losing  any  of  the  residue.  The  tube  is  again  filled  and 
shaken  as  before,  and  put  away  for  two  more  days.  After  the 
liquid  has  been  carefully  decanted  the  second  time,  the  tube,  with 
the  residue,  is  dried  at  a  low  temperature.  After  cooling  it  is 
weighed.  As  there  is  always  a  small  portion  of  the]  residue  poured 
off  in  the  solution  with  the  bitumen,  this  solution  must  be  evapo- 
rated and  the  bitumen  burned  off  in  a  platinum  dish  and  the 
weight  of  the  residue  added  to  that  in  the  tube.  The  weight  of 
the  sample  taken,  less  the  sum  of  these  two  weights,  is  the  weight 
of  the  bitumen  extracted,  from  which  can  be  calculated  the  per- 
centage of  bitumen  contained. 

Stability  of  the  Bitumen  at  High  Temperature.  —  The  necessity 
of  stability  at  high  temperature  for  a  length  of  time  is  owing  to 
the  length  of  time  the  bitumen  must  remain  in  a  heated  condition 
during  the  course  of  the  manufacture  of  the  asphalt  mixture, 
which  may  cause  it  to  lose  valuable  properties.  The  effect  of  this 
heat  is  rendered  much  more  severe  on  the  bitumen  because  of  its 
great  area  exposed  to  evaporation  when  mixed  with  sand.  The 
lack  of  stabilitj7  resulting  from  the  loss  of  light  oils  is  manifest  in 
different  ways  in  different  bitumens.  Although  generally  so,  it 
does  not  of  necessity  follow  that  the  bitumen  losing  the  most  oil 
undergoes  the  greatest  change  in  consistency.  There  are  two 
methods  of  testing  stability,  and  it  is  advisable  to  use  both. 

The  first  consists  in  making  the  asphalt  cement  into  a  mixture 
with  standard  sand  in  such  proportions  that  the  mixture  will  con- 
tain 10  per  cent  of  bitumen;  the  materials  for  the  mixture  are 


MATERIALS    EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS.     65 

kept  for  fifteen  minutes  in  an  oven  heated  to  300°  F.,  then  incor- 
porated by  stirring.  One  portion  of  the  mixture  is  put  aside  to 
cool,  while  the  other  is  kept  at  the  temperature  of  300°  F.  for 
one-half  hour  longer.  The  bitumen  is  then  extracted  from  both, 
and  after  reaching  the  same  temperature  their  penetrations  are 
oompared. 

The  second  method  consists  in  keeping  a  quantity  of  the  sub- 
stance, equivalent  to  20  grams  of  bitumen,  at  a  temperature  of 
400°  F.  for  thirty  hours.  The  method  of  procedure  is  as  follows: 
The  substance  is  weighed  in  a  short-necked,  tabulated,  2-ounce 
retort,  the  tare  of  which  has  been  previously  taken.  The  retort  is 
then  hung  in  a  copper  cylinder  so  that  the  neck  just  protrudes. 
The  copper  cylinder  is  then  jacketed  with  asbestos  and  provided 
with  a  thermometer.  After  being  heated  up  to  400°  F.,  at  which 
temperature  it  is  maintained  for  thirty  hours,  the  retort  is  allowed 
to  cool,  then  weighed  and  the  per  cent  of  loss  ascertained.  The 
retort  is  then  broken  and  the  character  of  its  contents  compared 
with  that  of  the  original  substance. 

Action  of  Water  and  Ammonia  on  the  Bitumen. — The  action  of 
water  and  dilute  ammonia  is  determined  by  moulding  an  inch  cube 
of  the  mixture  under  a  pressure  of  1000  pounds,  then  breaking  it 
into  two  pieces,  one  of  which  is  immersed  in  water  or  dilute  am- 
monia, while  the  other  is  kept  in  air.  The  two  pieces  are  com- 
pared from  time  to  time.  If  acted  on  by  the  liquid,  the  corners 
will  be  found  to  give  away  readily  with  a  slight  pressure  of  the 
finger.  After  soaking  some  time  it  is  well  to  evaporate  the  liquid 
to  dryness  and  note  if  any  bituminous  residue  remains. 

Changes  in  Bitumen  due  to  Age. — All  bitumens  undergo  a 
more  or  less  rapid  change  with  aging,  that  appears  to  be  due  to 
two  or,  possibly,  more  causes.  Two  distinct  changes  manifest 
themselves.  One  is  the  surface  hardening,  which  is  likely  duo  to 
indirect  oxidation,  and  possibly  to  the  volatilization  of  light  oils. 
It  begins  at  the  surface  and  gradually  extends  into  the  bitumen. 
The  other  is  a  hardening  of  the  entire  mass,  evidently  due  to 
polymerization.  Both  these  changes  take  place  in  all  bitumens, 
but  one  or  the  other  may  predominate.  The  former  is  much  the 
less  objectionable,  as  it  makes  slow  progress  into  the  mass.  In 
making  a  test  to  ascertain  the  effect  of  aging,  it  is  preferable  to 


66  HIGHWAY    CONSTRUCTION. 

use  the  asphalt  cement,  as  there  is  some  danger  in  using  extracted 
bitumen  of  the  solvent  not  having  been  entirely  removed,  and  its 
slow  evaporation  might  be  interpreted  as  a  true  change,  due  to  the 
hardening  of  the  bitumen. 

The  test  for  aging  is  made  as  follows:  The  penetration  of  the 
sample  is  determined,  after  which  it  is  put  away  for  a  week,  when 
it  is  again  ascertained.  If  the  sample  shows  an  appreciable  hard- 
ening, a  slanting  cut  is  made  into  it  with  a  sharp  knife,  laying 
over  the  upper  piece,  thus  exposing  a  gradual  descent  from  the 
surface  into  the  interior.  Penetrations  are  now  taken  down  the 
side  of  this  cut,  beginning  at  the  surface.  In  this  way  the  increase 
in  hardness  of  the  surface  and  the  interior  over  its  original  con- 
sistency is  determined ;  also  the  hardening  of  the  surface  over  the 
interior  and  the  depth  that  the  surface  hardening  has  entered  the 
sample. 

It  is  well  to  continue  this  test  for  as  long  a  period  as  possible, 
making  examinations  at  intervals  of  every  few  weeks. 

Susceptibility  of  Bitumen  to  Change  wilJi  Variations  in  Tem- 
perature.— This  is  determined  by  making  penetration  tests  of  the 
sample  at  several  different  degrees  of  temperature  and  noting  the 
changes  in  its  condition. 

Penetration  Tests. — The  softness  or  viscosity  of  an  asphalt 
cement  was,  in  the  early  days  of  asphalt  paving,  determined  by 
chewing  a  small  piece  and  judging  by  the  resistance  it  offered  to- 
the  teeth ;  the  rule  was  that  if  it  chewed  easily  and  yet  was  not 
soft  enough  to  adhere  to  the  teeth,  it  was  of  the  proper  consistency 
for  paving. 

Bowen's  Apparatus. — In  1888  Prof.  Bowen  devised  a  machine 
for  testing  the  viscosity  of  asphaltic  cements  which  has  been  exten- 
sively employed.  This  machine  consists  of  a  lever  about  17  inches 
long,  having  the  fulcrum  at  one  end  and  a  cambric  needle  inserted 
in  the  other  end,  above  which  is  placed  a  weight  of  100  grams. 
The  end  near  the  needle  is  connected  by  a  steel  rod  and  waxed 
cord  with  a  spindle  having  a  long  hand  which  moves  about  a  dial 
divided  into  360  degrees.  Another  cord  and  weight  upon  an 
enlarged  part  of  the  spindle  keeps  the  first-mentioned  cord  taut. 
By  a  suitably  contrived  spring  clip  the  steel  rod  can  be  released 
for  any  length  of  time,  and  the  needle,  which  has  first  been 


MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION   OF   PAVEMENTS.     67 

brought  to  coincide  with  the  surface  of  the  asphalt  cement  placed 
under  it  in  a  tin  box,  allowed  to  penetrate  under  the  action  of  the 
weight  into  the  cement.  The  number  of  degrees  through  which 
the  hand  moves  on  the  dial  records  the  penetration  of  the  cement; 
the  length  of  time  for  which  the  needle  is  released  is  one  second. 
Originally  Prof.  Boweii  selected  77°  F.  as  the  proper  temperature 
at  which  the  test  should  be  made,  and  brought  the  cement  and 
machine  to  this  degree  by  keeping  them  in  a  room  warmed  to  this 
point.  But  as  it  is  sometimes  inconvenient  or  impossible  to  have 
a  room  temperature  of  77°,  other  temperatures  may  be  made  avail- 
able by  placing  the  tin  sample-box  of  asphalt  cement  in  water  at 
77°  and  allowing  it  to  acquire  that  temperature,  when  the  test  can 
be  made  as  before,  certain  allowance  being  made  to  reduce  the 
result  to  the  normal  temperature  of  77°  F. 

Dow's  Apparatus. — Mr.  A.  W.  Dow,  Inspector  of  Asphalts  and 
Cements  at  Washington,  D.  C.,  has  devised  a  testing-machine  in 
which  he  has  endeavored  to  overcome  the  objections  raised  against 
Professor  Bowen's.  The  tests  are  made  in  a  water-jacketed  copper 
box;  any  temperature  can  be  obtained  in  this  box  by  running 
through  the  jacket  water  cooled  or  heated  as  desired.  The  needle 
penetrates  under  a  direct  weight  with  practically  no  friction.  The 
description  of  this  apparatus  in  detail  is  as  follows:  The  pene- 
trating needle,  which  is  an  ordinary  No.  '2  sewing  needle,  is  rigidly 
fastened  in  the  end  of  a  small  brass  rod.  This  rod  is  inserted  in 
the  end  of  an  aluminum  tube,  about  40  centimetres  in  length  and 
1  centimetre  in  diameter,  where  it  is  securely  fastened  by  means  of 
a  binding-screw.  By  filling  or  partially  filling  this  tube  with  mer- 
cury, it  can  be  made  of  any  desired  weight  from  30  to  300  grams, 
after  which  it  is  closed  by  a  cap  which  screws  on  to  the  end  oppo- 
site the  needle.  When  this  cap  is  screwed  into  place,  its  surface, 
which  is  perfectly  flat,  is  absolutely  at  right  angles  to  the  sides  of 
the  tube.  The  aluminum  tube  holding  the  needle  passes  down 
through  a  wooden  framework  in  which  it  is  held  in  a  vertical  posi- 
tion, with  the  needle-end  down,  by  means  of  a  jaw-clamp.  When 
this  clamp  is  released  the  tube  can  move  freely  up  and  down,  while 
it  is  retained  in  its  vertical  position  by  two  guides.  These 
guides  are  each  made  of  two  metal  plates  a  fraction  of  a  centimetre 
in  thickness.  Each  plate  has  a  semicircular  piece  cut  out  of  one 


68  HIGHWAY    CONSTRUCTION. 

side,  so  that  when  the  two  are  placed  together  it  leaves  a  circular 
opening  through  which  the  aluminum  tube  passes  freely,  but  yet 
not  so  freely  as  to  get  out  of  the  vertical.  To  facilitate  the  removal 
of  the  needle-tube  from  the  framework,  as  it  must  be  slightly 
inclined  while  withdrawing  so  as  to  clear  the  measuring  device,  the 
guides  are  constructed  so  that  one  plate  in  each  can  be  pushed  a 
short  distance  from  the  other,  thus  allowing  the  inclination  of  the 
tube.  These  plates  are  returned  to  their  original  position  by 
springs. 

In  the  upper  part  of  the  framework  directly  over  the  tube  is  a 
spindle  3.17  millimetres  in  diameter,  with  a  pointer  on  one  end 
which  turns  on  a  dial.  A  small  plumb-weight  is  suspended  from 
the  spindle  by  a  fine  platinum  thread  which  winds  on  it.  This 
weight  is  partly  counterbalanced  by  a  second  weight  suspended 
from  the  spindle  by  a  linen  thread.  These  weights  are  so  that  if 
they  be  allowed  to  move  freely  the  former  is  just  sufficiently  heavy 
to  cause  it  to  fall  gradually,  and  when  the  aluminum  tube  is  in  po- 
sition this  weight  will  fall  until  it  just  touches  the  surface  of  the 
cap  on  the  top  of  the  tube.  The  fall  of  one  centimetre  of  this 
weight  causes  the  spindle  to  make  one  revolution,  thus  making 
one  revolution  of  the  pointer  on  the  dial  equivalent  to  one  centi- 
metre. The  above  framework  is  fastened  on  to  the  cover  of  a 
copper  chamber,  the  aluminum  tube  projecting  through  this  cover 
into  the  chamber,  needle-end  down.  This  cover,  which  is  of 
wood,  is  made  in  two  thicknesses,  with  an  air-chamber  between, 
thus  more  perfectly  insulating  the  interior  of  the  chamber 
from  the  outside  air.  It  is  supplied  with  two  large  windows  on 
each  side  of  where  the  needle-tube  passes  in,  admitting  light 
and  allowing  the  operator  to  see  the  sample.  The  chamber  to 
hold  the  samples,  which  is  of  thin  sheet  copper,  is  constructed 
with  a  rounded  bottom  like  a  kettle,  and.  is  fitted  with  a  flat  false 
bottom  or  flooring  of  sheet  iron.  Raised  above  the  flooring  about 
an  inch,  resting  oh  three  rollers,  is  a  circular  disk,  on  which  the 
samples  to  be  tested  are  placed  in  a  circle  about  half  an  inch  from 
the  edge.  This  disk  can  be  rotated  like  a  turntable  by  means  of 
an  iron  rod  which  passes  through  its  centre  into  a  bearing  on  the 
floor  and  out  through  the  cover  of  the  chamber,  where  it  is  fitted 
with  a  wheel.  By  turning  this  wheel,  thus  revolving  the  disk, 


MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION   OF   PAVEMENTS.     69 

each  sample  on  it  can  be  brought  in  turn  under  the  penetrating 
needle.  In  this  way  twelve  samples  can  be  tested  by  this  particu- 
lar  apparatus  without  opening  the  chamber.  Two  swinging  mir- 
rors are  fastened,  one  on  each  side  of  the  copper  chamber,  one 
mirror  being  so  adjusted  as  to  throw  light  on  the  sample  to  be 
tested,  while  the  other  reflects  the  image  of  the  sample  so  that  it 
can  be  seen  by  looking  in  through  a  window  in  the  cover.  This 
copper  chamber  is  fastened  into  a  lead-lined  tank,  which  is  filled 
with  water  of  any  degree,  or  a  freezing  mixture,  as  the  case  may 
be,  to  produce  the  desired  temperature  in  the  chamber.  To  keep 
this  temperature  constant  the  tank  is  supplied  with  one  inlet,  in 
the  centre  of  the  bottom,  and  four  outlet  pipes,  one  on  each  side 
near  the  top.  The  temperature  of  the  copper  chamber  is  regulated 
by  a  simple  electrical  thermostat  suspended  in  it,  which  will  cut 
off  or  let  on  a  supply  of  liquid  or  water  entering  the  tank  as  the 
temperature  requires. 

In  making  a  test  or  tests  the  samples  are  placed  in  position  on 
the  disk  in  the  copper  chamber,  the  cover  with  the  apparatus  put 
in  place,  and  the  chamber  secured  in  the  lead-lined  tank.  The 
water  or  liquid  of  the  desired  temperature  is  run  into  the  tank, 
which  is  allowed  to  fill  and  run  off  by  the  overflow  pipes.  The 
entire  apparatus  is  then  levelled  by  levelling-screws  in  the  feet  of 
the  tank  until  the  needle-tube  is  perfectly  vertical.  When  asphalt 
is  to  be  tested  it  is,  for  convenience,  put  into  small  round  tins  like 
small  blacking  boxes.  By  heating  just  sufficiently  to  melt  it  a 
smooth  surface  is  obtained  with  quite  a  gloss.  These  boxes  con- 
taining the  samples  are  placed  on  the  revolving  disk,  each  sample 
resting  on  two  raised  points  on  the  surface  of  the  disk,  this  giving 
them  a  slight  incline.  The  table  is  then  revolved  until  the  de- 
sired sample  is  directly  under  the  needle-tube,  when  it  is  lowered 
until  the  needle  is  very  nearly  in  contact  with  the  surface.  The 
surface  of  the  sample  being  slightly  inclined,  it  can  be  brought  just 
in  contact  with  the  needle  by  a  slight  revolution  of  the  disk.  By 
arranging  the  mirror  on  top  of  the  cover  so  that  it  will  reflect  the 
light  from  a  window  down  upon  one  of  the  mirrors  in  the  chamber, 
which  in  turn  reflects  it  on  the  surface  of  the  sample,  and  then 
having  the  other  mirror  in  the  chamber  in  such  a  position  as  to 
reflect  the  image  of  the  sample  up,  the  needle  can  be  set  accurately 


70  HIGHWAY   CONSTRUCTION. 

to  the  surface  by  watching  its  reflection  in  the  surface  of  the  sam- 
ple. To  determine  the  penetration  the  reading  of  the  dial  is  taken, 
the  clamp  is  released,  which  allows  the  needle  to  sink  in  the  asphalt 
under  the  weight  of  the  tube.  The  apparatus  is  so  constructed 
that  when  the  clamp  is  released  from  the  tube  another  clamp  closes 
on  the  thread  of  the  counterbalance  weight,  thus  preventing  the 
plumb-weight  from  falling  and  adding  its  weight  to  that  of  the 
tube.  On  clamping  the  tube  again  at  the  expiration  of  the  desired 
time  the  thread  of  the  counterweight  is  released,  which  allows  the 
plumb-weight  to  sink  until  it  is  checked  by  the  top  of  the  tube. 
The  present  reading  of  the  dial,  less  that  before  taken,  is  the  dis- 
tance the  needle  penetrated  into  the  sample.  Headings  can  be 
made  with  accuracy  to  one-fiftieth  millimetre. 

District  of  Columbia  Standard. — The  present  standard  em- 
ployed for  penetration  tests  by  the  Engineer  Department  of  the 
District  of  Columbia  is  the  distance  (on  Dow's  apparatus)  expressed 
in  hundredths  of  a  centimetre  that  a  No.  2  needle  will  sink  or 
penetrate  into  an  asphalt  paving  cement  in  five  seconds  when 
weighted  with  100  grams,  the  cement  and  apparatus  being  at  a 
temperature  of  25°  C. 

The  average  penetration  (measured  by  the  above  standard)  of 
the  paving  cements  used  in  Washington,  D.  C.,  during  1899  was  : 

Eastern  Bermudez  Asphalt  Paving  Co 45 

Cranford  Paving  Co 36 

The  physical  tests  are  performed  in  the  usual  machines  em- 
ployed for  testing  other  cements. 

Tensile  Strength  of  Asphaltum. — Tests  of  the  tensile  strength 
of  asphalt  are  frequently  made  from  the  mixture  prepared  for  lay- 
ing in  the  street,  moulded  into  briquettes,  and  broken  in  a  similar 
manner  to  Portland  cement  briquettes.  This  method  is  imperfect, 
as  it  is  quite  impossible,  without  enormous  pressure,  to  get  the  par- 
ticles of  sand  as  firmly  consolidated  in  briquette  as  they  are  by  the 
kneading  and  rolling  motion  imparted  to  the  surface  mixture  under 
a  steam-roller,  and  whatever  advantage  is  to  be  found  in  this 
method  of  examination  it  is  complicated  by  any  variation  which 
may  occur  in  the  method  of  mixing. 

A  method  successfully  employed  to  obtain  the  tensile  strength 
of  asphalt  is  by  using  the  broken  halves  of  Portland  cement 


MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION   OF   PAVEMENTS.     71 

briquettes.  These  are  united  with  the  asphalt  or  asphaltic  cement, 
and  broken  in  a  testing-machine  in  the  following  manner:  The 
broken  halves  of  a  Portland  cement  briquette,  which  was  broken 
clean  and  at  right  angles  to  the  line  of  stress,  are  heated  to  drive 
off  all  moisture  ;  the  two  halves  are  then  dipped  in  molten  asphalt 
and  pressure  applied  by  hand  until  the  thickness  of  the  asphalt  is 
reduced  to  less  than  -fa  of  an  inch.  The  briquettes  are  then  al- 
lowed to  cool  slowly,  and  after  standing  24  hours  are  broken  in  a 
cement  testing-machine. 

Brass  briquettes  cast  from  the  pattern  of  a  Portland  cement 
briquette  are  also  used.  The  surfaces  upon  which  the  asphalt  is  to 
adhere  are  left  rough.  When  using  these  briquettes  they  are  heated 
to  about  140°  F.  in  water,  taken  out  and  dried,  and  the  separate 
ends  dipped  in  the  molten  asphalt.  The  two  ends  of  the  briquette 
are  then  stuck  together  and  allowed  to  cool  slowly  in  the  same 
manner  as  the  Portland  cement  briquettes. 

When  testing  asphaltic  cement  for  tensile  strength  the  penetra- 
tion of  the  cement  must  be  taken  into  consideration  as  well  as  the 
temperature  at  which  the  test  is  made.  Below  50°  F.  the  results 
obtained  will  be  very  much  more  regular  than  with  tests  made 
above  that  temperature;  the  higher  the  temperature  the  greater 
will  be  the  variation. 

An  asphaltic  cement  made  from  well  refined  Trinidad  Lake 
asphaltum  should  have  with  a  penetration  between  70  and  80  degrees 
(Bowen's  scale)  a  tensile  strength  of  over  450  Ibs.  per  sq.  in.  at 
a  temperature  of  35  degrees  Fahr.,  and  300  Ibs.  per  sq.  in.  at  50 
degrees  Fahr.,  the  strength  being  determined  with  a  one-inch  sec- 
tion, the  strain  to  be  applied  at  the  rate  of  1000  Ibs.  per  minute. 

The  ductility  or  property  of  being  drawn  out  in  long  threads 
or  strings  has  been  referred  to  in  Art.  1000  as  a  measure  of  the 
proper  consistency  of  a  paving  cement.  Mr.  W.  H.  Broadhurst, 
in  Proc.  A.  S.  M.  I.,  describes  the  method  employed  by  him  to 
measure  this  property  as  follows: 

Twenty  grams  of  pure  bitumen  were  extracted  from  Trini- 
dad, Bermudez,  and  Alcatraz  asphaltums  with  chloroform.  To  the 
pure  Trinidad  bitumen  petroleum  residuum  was  added  to  the 
amount  of  33  per  cent  of  its  weight  (this  percentage  being  calcu- 
lated from  the  usual  proportion  of  18  Ibs.  of  residuum  to  100  Ibs. 


HIGHWAY    CONSTRUCTION". 


of  refined  Trinidad  asphalt,  containing  55  per  cent  bitumen)^ 
The  penetration  was  then  taken  with  the  Bo  wen  apparatus,  and 
found  to  be  40°  at  80°  F.  The  pure  Bermudez  was  brought  to  the 
same  degree  of  penetration,  requiring  approximately  13  per  cent  of 
its  weight  of  petroleum  residuum.  The  pure  Alcatraz  bitumen 
required  approximately  24  per  cent  of  Alcatraz  maltha  (2X  grade) 
to  give  a  penetration  of  40°.  As  a  matter  of  technical  interest,  a 
separate  portion  of  Trinidad  bitumen  was  brought  to  40°  penetra- 
tion with  Alcatraz  maltha.  These  four  cements  were  poured  while 
hot  into  glass  tubes  2J  inches  in  length  and  -fa  inch  in  internal 
diameter,  closed  at  one  end  with  a  cylindrical  cork.  These  tubes 
had  previously  been  cut  in  half,  the  edges  ground  true  to  plane, 
and  cemented  together  with  a  thin  film  of  plaster  of  Paris.  This 
cement  joint  being  easily  broken  by  a  slight  side  pressure,  the 
tubes  were  kept  at  a  temperature  of  80° F.  for  one  hour;  they  wer& 
then  clamped  in  a  vertical  position  and  separated  a  distance  of 
exactly  J  of  an  inch.  The  lower  half  of  the  tube  was  then  allowed 
to  draw  apart  from  the  upper  by  its  own  weight,  thus  pulling  the 
cement  out  into  a  string,  the  cross-section  decreasing  as  the  length 
increased.  The  distance  between  the  tubes  at  the  time  of  .rupture 
was  noted,  and  the  following  results  were  obtained : 

RELATIVE  DUCTILITY  OF  ASPHALT  CEMENTS. 


Composition  of  Cement. 

Penetra- 
tion 
at  80°  F. 
Bowen's 
Scale 

Ductility 
at  8°  F. 
Length. 

Ductility 
at  90°  F. 
Length. 

Trinidad  asphaltum  and  petroleum  residuum. 
Bermudez  asphaltum  and  petroleum  residuum. 

40° 
40 
40 

iin. 

li 
gi 

fin. 

2-j  " 

4i  " 

Trinidad  Rspbaltuin  and  Alcatraz  maltha 

40 

24r 

4!  " 

Pure  Alcatraz  asphaltum  (soft)  

50 

4i 

Uvalde  asphaltum  (refined)  and  Alcatraz  maltha 
Trinidad  asphaltum  and  petroleum  residuum.  . 
Bermudez  asphaltum  and  petroleum  residuum  . 

50 
55 
55 
55 

s 

3* 

41 

Bukersfield  asphaltum  and  Bakersfield  maltha  . 

55 

3i 

As  asphalt  cement  possesses  the  same  qualities  and  can  be  used 
for  the  same  purposes  as  hydraulic  and  other  cements,  its  physical 
qualities  can  be  tested  in  a  similar  manner;  but  the  tests  which 


MATERIALS    EMPLOYED   IN   THE    CONSTRUCTION   OF    PAVEMENTS.     73 

have  been  made  and  published  have  been  conducted  without  any 
regard  to  uniformity  and  under  widely  different  .conditions;  there- 
fore they  are  of  little  or  no  value  in  determining  the  relative 
merits  of  the  cements. 

Uniformity  in  making  the  tests  would  accumulate  much  valu- 
able data  which  could  be  compared,  and  much  definite  information 
would  thus  be  gradually  collected  from  which  definite  conclusions 
could  be  ultimately  drawn. 

A  regular  system  of  analysis  and  examination  of  both  the  crude 
and  refined  asphiiltum,  the  oils  or  other  agent  used  for  fluxing, 
the  method  of  refining  the  asphaltum,  the  method  of  manufactur- 
ing the  asphaltic  cement,  the  sand,  stone-dust,  etc.,  should  be  main- 
tained in  all  cities  using  asphalt  pavements.  The  experience  thus 
gained  of  the  ^success  or  failure  of  pavements  made  of  different 
asphalts  will  serve  as  a  guide  for  similar  work  in  the  future.  This 
experience,  however,  will  not  serve  as  a  criterion  for  all  cities,  be- 
cause, owing  to  different  climatic  and  local  conditions,  the  propor- 
tions of  the  ingredients  in  the  cement  and  paving  mixture  must  be 
varied  to  suit  the  conditions  of  the  place  where  used;  therefore  the 
mixtures  which  are  successful  in  one  locality  may  become  failures  in 
another. 

In  comparing  the  relative  qualities  of  asphaltums  for  paving 
purposes  much  stress  is  frequently  laid  upon  the  amount  of  bitumen 
they  contain.  As  the  amount  of  bitumen  entering  into  the  paving 
mixture  is  less  than  20  per  cent  of  the  whole,  the  amount  of  bitumen 
contained  in  a  crude  asphaltum  can  in  no  way  affect  the  quality  of 
the  pavement;  but  its  quantity  does  affect  the  commercial  value  or 
price  of  the  crude  material  in  regard  to  the  amount  of  refined 
asphaltum  that  it  will  yield.  As  far  as  the  qualities  of  the  paving 
mixture  are  concerned,  it  is  the  character  and  condition  of  the 
bitumen,  and  not  its  quantity,  that  affect  the  results. 

Essential  Characteristics  of  a  Bitumen.— The  necessary  charac- 
teristics for  a  bitumen  to  possess  to  produce  a  satisfactory  pave- 
ment are  adhesiveness,  cohesiveness,  and  elasticity— to  a  certain 
degree.  It  must  not  show  too  rapid  a  change  with  aging,  must 
be  practically  unaffected  by  water  or  dilute  ammonia,  and  have  a 
proper  degree  of  consistency  or  softness.  Its  consistency  should 
not  be  greatly  altered  by  changes  in  temperature;  and  lastly,  a 


74 


HIGHWAY   CONSTRUCTION-. 


certain  degree  of  stability  upon  being  kept  at  a  high  temperature 
for  a  length  of  time. 

104.  Prices,  Production,  and  Imports  of  Asphaltum. — The  foU 
lowing  tables  show  the  comparative  prices  of  different  varieties  of 
asphaltum,  the  amount  of  the  domestic  production,  and  the  im- 
ports to  the  United  States  during  the  year  1897-98: 


TABLE  XVII. 
PRICES  OF  ASPHALTUM  IN  1897-98. 

Trinidad  crude,  at  New  York $13.00          per  ton 

refined,  at  New  York $30.00  to  $40.00  './«-  ' 

Hard  Cuban,  at  New  York 28.00  " 

Gilsonite,  at  the  mines 60.00  " 

Bituminous  rock; 

California,  at  the  mines 3.25  to  12.00  " 

Kentucky,  at  the  mines .             3.25  " 

California  refined  (hard),  at  the  works 17.50  to    19.50  " 

at  New  York 26.50  to    32.00  " 

California  refined  (maltha),  at  the  works.. .    20.00  to    22.00  ""  '  ' 

at  New  York..   29.00  to    34.50  :**tU 

Wasatch  bituminous  limestone,  at  the  works           18.00  " 


TABLE  XVIII. 
PRODUCTION  OP  ASPHALTUM  IN  THE  UNITED  STATES. 


18< 

)7. 

18 

98. 

State. 

Short 
Tons. 

Value. 

Short 
Tons. 

Value. 

68,650 

$598  502 

71  086 

$605  451 

3,250 

15  150 

1  450 

7  800 

Indian    Territory,    Oklahoma,    and 
Texas                  

345 

3  480 

1  635 

7  952 

3,700 

47,500 

2J66 

54  446 

Total          .           

75,945 

$664  632 

76  337 

$675  649 

MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION   OF   PAVEMENTS.     75 


TABLE 
VARIETIES  OF  ASPHALTUM,  ETC.,  PRODUCED  IN  THE  UNITED  STATES. 


Variety. 

18 

97. 

18 

38. 

Short  Tons. 

Value. 

Short  Tons. 

Value. 

Crude  aspbaltum  

5  971 

$71  ,404 

11  300 

$179  900 

48  801 

158  914 

43  624 

126  831 

Bituminous  limestoiie 

2  100 

10  600 

5  502 

26  412 

Mastic            

488 

9,864 

1  158 

17  840 

Hard  and  refined  or  gum  

3  940 

102  500 

1  878 

53  666 

14,650 

311  350 

12,875 

271  000 

Total        

75  945 

$664  632 

76  337 

$675  649 

TABLE  XIX. 
IMPORTS  OF  ASPHALTUM  TO  THE  UNITED  STATES. 


189 

189 

3. 

Long  Tons. 

Value. 

Long  Tons. 

Value. 

West  Indies  : 
British  (Trinidad)  

85,034 

$198  786 

71  992 

$217  660 

400 

2  000 

Cuba  

223 

4  180 

137 

2  172 

98 

530 

14  580 

77  456 

1  260 

7  531 

Venezuela  (Bermudez)  

13  807 

75  943 

2000 

10  006 

Germany  

6  896 

25,986 

2,302 

9,066 

861 

3,327 

779 

3,377 

Mexico           .     ...     . 

273 

3  992 

438 

5,773 

Turkey  in  Asia  

31 

3,439 

41 

3,744 

11 

309 

13 

597 

United  States  of  Colombia 

3 

130 

9 

Canada 

2 

6 

Total  

122,122 

$395,554 

79,060 

$260,765 

105.  Uses    of  Asphaltum.— Refined    asphaltum   and   asphaltic 
cement  are  extensively  used  in  all  branches  of  engineering.     The 
paving  industry  absorbs  about  60  per  cent  of  the  domestic  produc- 
tion and  about  80  per  cent  of  the  imported.     Of  the  imports  from 
Trinidad  about  90  per  cent  is  employed  for  street-paving. 

106.  Paving-pitch. — This  is  the  name  given  to  the  tar  pro- 
duced in  the  manufacture  of  gas.     It  is  also  known  as  gas-tar,  coal- 


76  HIGHWAY   CONSTRUCTION. 

tar,  etc.  When  the  tar  is  redistilled,  the  product  is  called  coal-tar 
distillate,  and  is  numbered  Distillate  No.  1,  2,  3,  4,  etc.,  according 
to  the  density  or  specific  gravity.  The  character  of  the  tar  varies 
with  the  system  of  carbonization  and  temperature  employed. 
There  are  several  tars  on  the  market  which  show  to  the  analyst  no- 
material  difference,  although  the  grouping  and  character  of  the 
constituents  are  different.  Some,  when  used  for  paving  purposes, 
will  become  hard  and  brittle  in  a  few  months,  and  others  will  not 
harden  or  set. 

The  pitch  known  as  No.  4  is  used  mainly  as  a  filler  for  granite 
and  Belgian  block.  It  is  very  soft,  and  frequently  becomes  semi- 
fluid under  the  heat  of  summer;  for  this  reason  it  is  put  up  in  oil 
barrels  which  contain  about  50  to  52  gallons. 

The  No.  6  is  generally  used  as  a  filler  for  brick  pavement;  it  is- 
termed  medium  hard,  and  is  commonly  put  up  in  cement  and  lime 
barrels.  The  cement  barrels  contain  about  28  gallons,  and  the 
lime  barrels  from  30  to  32  gallons.  The  pitch  is  sold  by  the  ton, 
and  the  weight  of  the  package  is  figured  in. 

A  square  yard  of  brick  paving  requires  from  1  to  1£  gallons, 
according  to  the  spacing  and  the  manner  in  which  the  work  is 
done.  A  square  yard  of  stone-block  paving  will  take  from  2  to  4 
gallons. 

Paving-pitch  is  frequently  adulterated  with  wood-pitch,  which 
serves  to  reduce  its  cost  considerably,  and  also  serves  to  make  it 
very  inferior  for  paving  purposes.  A  paving-pitch  suitable  for 
stone  pavements  should  be  soft  enough  to  almost  stick  to  the 
fingers  when  worked  in  the  hand  at  a  temperature  of  about  70°  F. 
For  brick  pavements  it  should  be  somewhat  harder,  so  as  to  check 
the  tendency  to  flow  during  hot  weather. 

The  use  of  coal-tar  as  a  cementing  medium  for  carriageway 
pavements  has  been  practically  abandoned  in  the  United  States,  but 
in  the  country  towns  of  England  it  is  still  extensively  employed 
for  foot-paths,  floors,  etc. 

Analysis  of  No.  4  pitch  gives  the  following  composition :  Spe- 
cific gravity,  1.284  to  1.309;  matter  soluble  in  carbon  bisulphide, 
64.84  to  72.50;  insoluble  matter,  27.50  to  35.16. 

The  price  per  gallon  at  the  gas-works  during  1898  varied  from 
2.23  cents  in  Indiana  to  10.17  in  Montana  and  New  Mexico. 


MATERIALS    EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS,      77 

Many  persons  consider  that  the  enduring  quality  of  the  tar  is 
increased  by  the  addition  of  refined  aaphaltum,  and  specifications 
frequently  call  for  the  addition  of  from  10  to  20  per  cent  of  as- 
pbalturn;  but  this  clause  is  rarely  complied  with,  and  it  is  doubt- 
ful if  the  mixture  would  prove  beneficial,  because  the  materials, 
although  very  similar  in  appearance  and  in  some  of  their  charac- 
teristics, are  entirely  different  in  composition. 

(See  also  Art.  160.) 

107.  Brick — Clay. — Pure  clay  consists  of  a  hydrated  silicate  Of 
alumina  in  combination  more  or  less  with  other  substances  derived 
from   the   felspathic    rocks,   which    by   their    disintegration    and 
decomposition  have  formed  the  clay.     The  chemical  formula  of  the 
most  prominent  varieties  of  clay  according  to  Brogniart  and  others 
may  be  expressed  by  2Al2033Si024HO. 

108.  Pure  clay  is  soft,  more  or  less  unctuous  to  the  touch; 
white  and  opaque,  and  when  breathed  upon  emits  a  characteristic 
odor.     It   is   infusible,   and   insoluble   either   by  water,   nitric   or 
hydrochloric  acids.     It  may  be  converted  by  water  into  a  doughy, 
tenacious,  plastic  paste.     It  absorbs  water  with  avidity,  but  when 
burned  at  a  sufficiently  high  temperature   it  becomes  hard  and 
gritty   and   loses   almost   wholly   or    altogether    this   property   of 
combining  with  water.     When  slowly  dried  and  exposed  to  red 
heat,  the  particles  of  clay  are  augmented  in  volume  and  possess  less 
density.     At  the  same  time,  however,  the  interstitial  spaces  are 
diminished  and  they  approach  more  closely  together,  giving  an 
increase  of  density  to  the  whole  mass  of  burnt  clay,  which  is  prac- 
tically observed  by  a  diminution  of  surface  and  technically  called 
the  shrinking  of  the  clay.     This  shrinkage  is  very  materially  modi- 
fied  and   affected   by  the   admixture   and   proportion   of  foreign 
matters  possessing  other  properties. 

109.  In  nature  the  greater  number   of  clays  is  found  inter- 
mingled with  other  substances  foreign  to  them  in  their  original 
localities.     The  usual  constituents  of  clay  are  alumina,  silica,  iron, 
lime,  magnesia,  and  alkalies,  all  of  which  modify  the  character  of 
the  clay  and  its  applications,  according  as  one  or  other  of  these  in- 
gredients predominates. 

110.  The  ingredients  which  most  affect  the  character  of  the 
clay  are  the  silica,  iron,  and  lime,  and  its  plasticity  diminishes  in 
proportion  to  the  amount  of  any  one  of  these  substances  which  it 
contains,  as  they  are  not  plastic.     Sand  exercises  the  most  marked 


78  HIGHWAY   CONSTRUCTION. 

effect ;  it  possesses  no  binding  properties,  and  alone  it  is  infusible 
except  at  the  highest  temperatures  of  the  oxyhydrogen  blowpipe. 
Bricks  made  of  clay  containing  an  excess  of  sand  are  rough  and 
weak.  Iron  renders  clay  fusible,  and  its  presence  is  objectionable  in 
brick  intended  for  furnace-lining;  but  in  paving-brick  it  is  advan- 
tageous, making  the  brick  more  homogeneous.  Lime,  although 
infusible,  is  at  high  temperatures  changed  into  caustic  lime,  ren- 
ders the  clay  fusible,  and  when  exposed  to  the  action  of  the 
weather  absorbs  moisture  and  causes  disintegration.  Its  presence 
is  to  be  avoided  in  clay  used  for  the  manufacture  of  paving-brick. 
Magnesia  exerts  but  little  influence  on  the  character  of  the  clay ;  in 
small  quantities  it  renders  the  clay  fusible;  at  60  degrees  Fahr.  its. 
crystals  lose  their  water  of  crystallization  and  cold  water  decom- 
poses them,  forming  an  insoluble  hydrate  in  the  form  of  a  white 
powder.  In  air-dried  brick  this  action  causes  them  to  crack.  The- 
alkalies  are  found  in  small  quantities  in  the  best  of  clays;  from 
1  to  3  per  cent  renders  the  clay  fusible.  The  greater  the  amount 
of  quartz  and  silica  that  enters  into  the  composition  of  the  clay,  the 
more  difficult  it  will  be  of  fusion. 

111.  Clay,  to  make  a  good  paving-brick,  must  be  rich  in  silica,, 
free  from  lime,  and  able  to  withstand  without  fusing  a  red  heat 
for  a  sufficient  length  of  time  to  render  the  bricks  hard,  homoge- 
neous, and  impervious  to  water. 

112.  Common  hard:burned  brick  is  not  suitable  for  paving  pur- 
poses, although  such  brick  makes  a  smooth  pavement  under  light 
traffic  and  lasts  for  a  number  of  years;  still,  under  the  influence  of 
moisture  and  frost,  disintegration  is  inevitable  in  the  end.     ~Noi 
will  such  brick  sustain  constant  heavy  traffic,  aside  from  climatic 
influences.     Brick  made  of  suitable  clay,  however,  will  stand  the 
severest  frosts,  and  crushing   tests   show  it  to  be  equal  to  many 
granites. 

The  shales  or  rock-like  clays  are  now  almost  exclusively  used 
in  tho  manufacture  of  paving-brick.  They  usually  contain  a  high 
perccn:.igo  of  fluxing  impurities,  which  enables  them  to  be  readily 


A  very  elaborate  discussion  of  the  chemical  composition  and  the  influence 
of  impurities  of  clays  is  given  by  H.  A.  Wheeler,  Assistant  Geologist  in  Part  I 
of  the  "Report  on  the  Missouri  Clays." 


MATERIALS   EMPLOYED   IN   THE    CONSTRUCTION"   OF   PAVEMENTS.    79 

vitrified.     The  average  composition  of  the  shales  that  have  proved 
satisfactory  for  the  manufacture  of  paving-brick  is  as  follows: 

Silica  (SiO,) 56.00 

Alumina  (A12O2) 22.00 

"Water  chemically  combined  and  loss  on  ignition 7.00 

Moisture  (H2O) 2. 00 

Sesquioxide  of  iron  (Fe2O3) 7.00 

Lime  (CaO) 1.00 

Magnesia  (MgO) 1.00 

Alkalies  (K2ONa2O) ,  4.00 


100.00 

113.  The  color  of  clay  is  of  no  practical  importance  ;  it  is  due 
to  the  presence  of  metallic  oxides  and  organic  substances.     Clay 
containing  iron  produces  bricks  which  are  either  red,  yellow,  or 
blue,  according  to  the  quantity  of  the  oxide  present  and  the  de- 
gree of  heat  to  which  they  have  been  subjected;  some  organic  sub- 
stances produce  a  blue,  bluish-gray,  or  black  color. 

The  color  of  the  brick  is  largely  influenced  by  the  burner  in 
the  manipulation  of  the  fires,  and  cannot  be  relied  upon  as  a  guide 
to  the  quality  of  the  brick;  for  a  specific  clay  and  a  given  burner 
it  aids  in  estimating  the  degree  to  which  the  brick  has  been  burned,, 
and  the  care  with  which  it  has  been  handled. 

114.  The  Manufacture  of  Paving-brick  may  be  classified  under 
the  following  heads : 

Excavation  of  the  day  either  by  hand  labor  or  mechanical 
appliances. 

Preparation  of  the  clay  consists  in  (a)  removing  gravel,  stones,- 
or  other  mechanical  impurities;  (b)  pulverizing  the  clay.  This  is 
performed  either  by  toothed  rolls,  centrifugal  disintegrators,  or 
crushing-rolls  in  the  revolving  dry  or  wet  pan.  The  dry  pan  with  a 
perforated  grate  bottom  is  generally  employed  for  shales  and  fire 
clays. 

The  pulverized  clay  is  usually  screened  in  either  revolving 
trammels  or  fixed  or  shaking  riddles,  with  4  to  ]6  meshes  to  the 
linear  inch.  The  degree  of  fineness  of  the  screen  is  a  very  impor- 
tant matter,  as  the  finer  the  clay  the  more  plastic  it  is,  and  hence 
the  more  homogeneous  and  stronger  the  brick.  The  fineness  of  the 
screen,  however,  must  be  determined  for  each  specifically,  us  ex- 


80  HIGHWAY   CONSTRUCTION". 

cessive  fineness  in  some  clays  causes  checking  and  cracking  in 
drying  or  burning,  and  aggravates  the  trouble  from  laminations. 
In  some  works  the  clay  is  not  screened  any  further  than  is  accom- 
plished by  the  screen-plates  of  the  dry  pan,  which  are  usually  £  to 
%  inch  in  width. 

Tewiiering. — The  screened  clay  is  mixed  with  water  and  worked 
to  a  more  or  less  plastic  mass  in  a  pug-mill.  The  operation  should 
be  performed  in  such  a  way  as  to  secure  a  thorough,  uniform  mix- 
ture of  the  clay  and  water;  if  this  is  not  attained  the  clay  leaves 
the  machine  with  variable  amounts  of  water.  This  causes  check- 
ing and  cracking  in  the  drying,  and  sometimes  in  the  burning, 
with  marked  variations  in  the  strength  of  the  brick.  The  more 
thoroughly  a  clay  is  pugged,  the  more  plastic  it  is  rendered,  and 
the  more  uniform  and  reliable  will  be  the  quality  of  the  brick. 

Moulding. — The  process  most  generally  employed  for  moulding 
paving-brick  is  that  called  the  "  stiff-mud  process."  The  clay  is 
made  into  a  stiff,  plastic  mud,  which  is  forced  through  a  die  by  a 
continuous-working  auger  or  intermittent  plunger  as  a  bar  of  clay, 
which  is  then  cut  by  wires  into  suitable  lengths. 

For  forming  the  bar  of  clay  two  types  of  dies  are  employed;  in 
one  the  die  is  approximately  3"  X  4"  in  section,  and  the  bar  of  clay 
is  cut  into  9"  lengths;  this  is  known  as  the  "  end-cut  system" :  in  the 
other  the  die  is  approximately  4"  X  9"  in  section,  and  the  bar  of 
clay  is  cut  into  3"  lengths;  this  is  called  the  "side-cut  system." 
There  is  considerable  difference  of  opinion  as  to  the  relative 
merits  of  these  two  methods  of  moulding. 

Drying. — The  moulded  brick  are  packed  in  cars,  in  open 
checker  work,  direct  from  the  brick- machine,  which  are  run  into 
chambers  or  tunnels  heated  by  open  fires,  steam -coils,  or  a  heated 
blast.  The  time  required  for  drying  depends  upon  the  character 
of  the  clay;  the  finer  and  more  plastic  the  clay  the  greater  the 
time  required,  the  coarser  and  leaner  the  clay  the  more  rapidly  it 
can  be  dried.  Some  clays  can  be  safely  dried  in  24  hours,  while 
others  require  from  00  to  72  hours. 

Burning. — After  being  sufficiently  dried  the  bricks  are  piled  in 
the  kilns,  and  the  firing  is  conducted  with  the  utmost  care,  as  upon 
it  the  perfection  of  the  brick  largely  depends.  Two  classes  of  kilns 
are  in  use  for  burning  paving-brick,  the  down-draft  and  the 


MATERIALS    EMPLOYED    IN   THE    CONSTRUCTION    OF    PAVEMENTS.     81 

continuous.  The  down-draft  type  seems  to  be  the  most  pre- 
ferred, as  with  careful  handling  from  60  to  90  per  cent  of  No.  1 
brick  can  be  obtained.  The  continuous  type  has  greater  economy 
of  fuel,  but  the  shrinkage  and  the  difficulty  of  securing  uniformity 
in  burning  is  so  great  that  they  only  yield  from  40  to  70  per  cent 
of  No.  1  brick.  After  the  brick  are  burned,  the  kiln  is  tightly 
closed  to  shut  off  the  access  of  cold  air,  and  the  longer  the  time 
given  the  brick  to  cool  and  anneal  the  tougher  the  brick  will  be. 

Sorting. — In  emptying  the  kiln  there  are  usually  three  grades 
of  brick  found :  (1)  Those  which  have  received  the  highest  heat, 
and,  while  hard,  are  not  generally  tough  enough  for  paving  pur- 
poses; (2)  those  which  have  not  received  sufficient  heat  to  be  prop- 
erly vitrified;  and  (3)  those  which  have  been  properly  burned,  and 
which  are  designated  as  No.  1,  or  strictly  first-class  paving-brick. 
They  are  distinguished  by  the  fracture,  toughness,  and  the  color 
from  the  other  two  grades  of  brick.  They  should  be  perfectly  uni- 
form in  the  fracture,  homogeneous,  very  dense,  very  hard,  tough, 
and  reasonably  free  from  "kiln-marks/'  or  indentations  made  by 
the  overlying  brick.  The  depth  of  the  kiln-mark  is  considered  a 
gauge  for  the  degree  of  the  vitrification;  the  deeper  the  mark  the 
more  thorough  the  vitrification,  but  if  too  deep  they  make  a  rough 
uneven  pavement;  the  allowable  limit  ranges  from  -J  to  f  inch. 
The  absence  of  kiln-marks  usually  indicates  underburning.  Ex- 
cept in  fire-clays,  it  is  seldom  that  a  properly  vitrified  brick  is 
entirely  free  from  slight  indentations. 

115.  Repressed  Brick  are  produced  by  subjecting  the  brick  im- 
mediately after  it  leaves  the   brick- machine,  and  while  still  in  a 
plastic  condition,  to  a  moderate  vertical  pressure  in  a  metal  mould- 
box.     The  operation  fills  out  the  edges  and  angles,  and  rounds 
them  if  desired.     The  appearance  of  the  brick  is  much  enhanced, 
but  there  is  much  difference  of  opinion  as  to  whether  the  quality  is 
improved;  the  tests  by  Professor  Orton  indicate  that  repressing 
an  end-cut  brick  improves  it,  while  repressing  a  side-cut  brick 
injures  it. 

116.  Analyses  of  Clay.— Table  XX  shows  the  composition  of 
some  of  the  clays  used  in  the  manufacture  of  paving-brick. 


82 


HIGHWAY   CONSTRUCTION. 


TABLE   XX. 

ANALYSES  OF  CLAYS. 


o 

M 

03 

3 

be 
i», 

"6 

.2     1 

Locality. 

= 

•s 

—  ' 

*4 

<£ 

"3 

W.2 

.S 

|L  i 

1 

£ 

c 

Fi 

1 

* 

0. 

1 

|.S 

03,0 

«F 

a 

I? 

J 

53 

3 

& 

3 

£ 

OJ 

02 

0 

* 

EH 

V 

oi 

Woodbridge,  N.  J. 

42.23 

39.53 

0.5 

0.1 

0.41 

0.08 

13.59 

1.21 

a.  40 

o.5a 

42.05 

•J5  83 

0.77 

1,11 

0,44 

12.20 

1.50 

1.10 

5.70 

Phillipsburg,     "•• 

56.78 

17.38 

6.50 

4.14 

3.15 

3 

.42 

6.89 

7 

.60 

6.13  .... 

Winchester,  111  

23.15 

17.08 

3.47 

1.28 

1.10 

6.30 

1.20 

0.90 

46.70 

Bloomiugtou,  III 

67.80 

11.55 

4.3118.90 

5.32 

2 

.42 

.... 

trace 

0 

.20 

trace 

Cheltenham,  Mo  . 

61  22 

25  64 

1  70 

1 

31 

0  4 

9.68 

38.1(1 

•JJ.53 

2.32 

tr. 

0  40 

11.30 

2.50 

1.50 

12.70 

Montgomery,  Mo. 

43.93 

40.09 

0.88 

0  20 

13.80 

0  80 

tr.* 

0.60 

Woodlawn,  Penn. 

42  15 

31  43 

1  57 

0  3'? 

2  01 

9.40 

1  20 

1  00 

10.25 

Mt.  Savage,  Md.. 

39.90 

30.08 

1.67 

2.30 

7.00 

6.90 

1.15 

16.90 

Carter  Co.,  Ky.  .. 

46  75 

38.17 

0  29 

0  57 

ft  !'-> 

o 

07 

14 

03 

Marion  Co   W  Va 

59  25 

32  26 

7  1fi 

1 

33 

San  Fran.,  Cal. 

56  51 

21.33 

12  31 

8  53 

tr 

.... 

6  30 

Hayclensville,  O 

72  24 

16  87 

0  16 

0  50 

tr 

1 

09 

5  14 

Burlington,  la 

77.40 

11.74 

3.29 

1  60 

1  91 

3  76 

0  47 

Clinton,          " 

73  82 

15  88 

2  92 

tr 

tr 

4  5 

3  0 

Morrison,  Colo. 

71.8 

15.0 

tr. 

3  8 

8.3 

Golden         " 

52  41 

32  21 

0  66 

0  20 

0  61 

0  61 

14  05 

Stourbridge,  Eng 

67  34 

23  03 

2  03 

S8 

8  24 

64.05 

23.15 

1.85 

0 

.10 

10.00 

*  With  A12OS . 

117.  The  Characteristics  of  Brick  suitable  for  Paving  are: 

(1)  Not  to  be  acted  upon  by  acids. 

(2)  Not  to  absorb  more  than  -g-J^-  of  its  weight  of  water  in  48- 
hours. 

(3)  Not  susceptible  to  polish. 

(4)  Rough  to  the  touch,  resembling  fine  sandpaper. 

(5)  To  give  a  clear  ringing  sound  when  struck  together. 

(6)  When  broken  to  show  a  compact,  uniform,  close-grained 
structure,  free  from  air-holes  and  pebbles. 

(7)  Not   to   scale,  spall,  or  chip  when   quickly  struck   on   the 
edges. 

(8)  Hard  but  not  brittle. 

118.  Tests  of  Paving-brick.     To  ascertain  the  quality  of  paving- 
brick  they  are    now  generally  subjected    to    four  tests,  namely: 

(1)  Abrasion    by  impact   (commonly  called  the  "Kattler"   test);. 

(2)  absorption;   (3)    transverse   or   cross-breaking;    (4)    crushing. 
"With  the  view  of  securing  uniformity  in  the  methods  of  making 


MATERIALS   EMPLOYED    IN   THE    CONSTRUCTION   OF   PAVEMENTS.    83 

the  above  tests  the  National  Brick  Manufacturers7  Association  have 
adopted  and  recommend  the  following: 

118a.  Standard  Tests  Adopted  by  the  National  Brick  Manufac- 
turers7 Association  (Chicago,  Jan.  27,  1900). 

RATTLER   TEST. 

1.  Dimensions  of  the  Machine. — The  standard  machine  shall  be 
28  inches  in  diameter  and  20  inches  in  length,  measured  inside  the 
chamber. 

Other  machines  may  be  used  varying  in  diameter  between  26 
and  30  inches,  and  in  length  from  18  to  24  inches,  but  if  this  is 
done,  a  record  of  it  must  be  attached  to  the  official  report.  Long 
rattlers  may  be  cut  up  into  sections  of  suitable  length  by  the  inser- 
tion of  an  iron  diaphragm  at  the  proper  point. 

2.  Construction  of  the  Machine. — The  barrel  shall  be  supported 
on  trunnions  at  either  end;  in  no  case  shall  a  shaft  pass  through 
the  rattling  chamber.     The  cross-section  of  the  barrel  shall  be  a 
regular  polygon  having  fourteen  sides.    The  heads  shall  be  composed 
of  gray  cast  iron,  not  chilled  or  case-hardened.     The  staves  shall 
preferably  be  composed  of  steel  plates,  as  cast-iron  peans  and  ulti- 
mately breaks  under  the  wearing  action  on  the  inside.    There  shall 
be  a  space  of  one-fourth  of  aii  inch  between  the  staves  for  the 
escape  of  dust  and  small  pieces  of  waste.     Other  machines  may  be 
used,  having  from  twelve  to  sixteen  staves,  with  openings  from  one- 
eighth  to  three-eighths  of  an  inch  between  staves,  but  if  this  is 
done  a  record  of  it  must  be  attached  to  the  official  report  of  the 
test. 

3.  Composition  of  the  Charge, — All  tests  must  be  executed  on 
charges  containing  but  one  make  of  brick  or  block  at  a  time.     The 
charge  shall  consist  of  nine  paving-blocks  or  twelve  paving-bricks, 
together  with  300  pounds  of  shot  made  of  ordinary  machinery  cast 
iron.     This  shot  shall  be  two  sizes,  as  described  below,  and  the  shot 
charge  shall  be  composed  of  one-fourth  (75  pounds)  of  the  larger 
size,  and  three-fourths  (225  pounds)  of  the  smaller  size. 

4.  Size   of  the  Shot.— The   larger   size   shall  weigh   about   7£ 
pounds  and  be  about  2-|-  inches  square  and  4J  inches  long,  with 
slightly  rounded  edges.     The  smaller  size  shall  be  cubes  of   1£ 
inches  on  a  side,  with  rounded  edges.     The  individual  shot  shall 


84  HIGHWAY    CONSTRUCTION". 

be  replaced  by  new  ones  when  they  have  lost  one-tenth  of  their 
original  weight. 

5.  Revolutions  of  the  Charge. — The  number  of  revolutions  of  a 
standard  test  shall  be  1800,  and  the  speed  of  rotation  shall  not  fall 
below  28  nor  exceed  30  per  minute.     The  belt-power  shall  be  suffi- 
cient to  rotate  the  latter  at  the  same  speed,  whether  charged  or 
empty. 

6.  Condition  of  the  Charge. — The  bricks  composing  a  charge 
shall  be  thoroughly  dried  before  making  the  test. 

7.  Calculation  of  the  Results. — The  loss  shall  be  calculated  in 
per  cents  of  the  weight  of  the  dry  brick  composing  the  charge,  and 
no  results  shall  be  considered  as  official  unless  it  is  the  average  of 
two  distinct  and  complete  tests  made  on  separate  charges  of  brick. 

ABSORPTION   TEST. 

1.  The  number  of  bricks  for  a  standard  test  shall  be  five. 

2.  The  test  must  be  conducted  on  rattled  brick.     If  none  such 
are  available,  the  whole  brick   must  be  broken  in  halves  before 
treatment. 

3.  Dry  the  bricks  for  forty-eight  hours  at  a  temperature  ranging 
from  230°  to  250°  F.  before  weighing  for  the  official  dry  weight. 

4.  Soak   for   forty-eight   hours   completely  immersed   in  pure 
water. 

5.  After   soaking,   and  before  weighing,   the   bricks   must   be 
wiped  dry  from  surplus  water. 

6.  The  difference  in  the  weight  must  be  determined  on  scales 
sensitive  to  one  gram. 

7.  The  increase  in  weight  due  to  water  absorbed  shall  be  calcu- 
lated in  per  cents  of  the  initial  dry  weight. 

CROSS-BREAKING   TEST. 

1.  Support  the  brick  on  edge,  or  as  laid  in  the  pavement,  on 
hardened  steel  knife-edges,  rounded  longitudinally  to  a  radius  of 
twelve  inches  and  transversely  to  a  radius  of  one-eighth  inch,  and 
bolted  in  position  so  as  to  secure  a  span  of  six  inches. 

2.  Apply  the  load  to  the  middle  of  the  top  face  through  a  har- 


MATERIALS   EMPLOYED    IN   THE    CONSTRUCTION-   OF   PAVEMENTS.    85 

dened  steel  knife-edge,  straight  longitudinally  and  rounded  trans- 
versely to  a  radius  of  one-sixteenth  inch. 

3.  Apply  the  load  at  a  uniform  rate  of  increase  till  fracture 
ensues. 

4.  Compute  the  modulus  of  rupture  by  the  formula  /  —  ^T-™, 
in  which /  =  modulus  of  rupture  in  pounds  per  square  inch; 

w  =  total  breaking  load  in  pounds; 
I  =  length  of  span  in  inches  =  6"; 
I  =  breadth  of  brick  in  inches; 
d  =  depth  of  brick  in  inches. 

5.  Samples  for  test  must  be  free  from  all  visible  irregularities  of 
surfaces  or  deformities  of  shape,  and  their  upper  and  lower  faces 
must  be  practically  parallel. 

6.  Not  less  than  ten  brick  shall  be  broken,  and  the  average  of 
all  be  taken  for  a  standard  test. 

CRUSHING    TEST. 

1.  The  crushing  test  should  be  made  on  half-bricks,  loaded  edge- 
wise, or  as  they  are  laid  in  the  street.     If  the  machine  used  is 
unable  to  crush  a  full  half-brick,  the  area  may  be  reduced  by  chip- 
ping  off,  keeping  the  form  of  the  piece   to  be  tested  as  nearly 
prismatic  as  possible.     A  machine  of  at  least  one  hundred  thou- 
sand pounds  capacity  should  be  used,  and  the  specimen  should  not 
be  reduced  below  four  square  inches  of  area  in  cross-section  at  right 
angles  to  direction  of  load. 

2.  The  upper  and  lower  surfaces  should  preferably  be  ground 
to  true  and  parallel  planes.     If  this  is  not  done,  they  should  be 
bedded  while  in  the  testing-machine  in  plaster  of  Paris,  which 
should  be  allowed  to  harden  ten  minutes  under  the  weight  of  the 
crushing  planes  only,  before  the  load  is  applied. 

3.  The  load  should  be  applied  at  a  uniform  rate  of  increase  to 
the  point  of  rupture. 

4.  Not   less  than  an  average  obtained  from  five  tests  on  five 
different  bricks  shall  constitute  a  standard  test. 


86  HIGHWAY    CONSTRUCTION-. 

119.  Specific  Gravity,  Weight,  Resistance  to  Crushing,  and  Ab- 
sorptive Power  of  Paving-brick.  In  regard  to  these  qualities  the 
paving-bricks  made  by  different  manufacturers  and  by  the  same 
manufacturer  vary  considerably,  as  will  be  seen  from  Table  XXI. 
In  weight  they  vary  from  5  to  7-j-  pounds;  in  specific  gravity,  from 
1.91  to  2.70;  in  resistance  to  crushing,  from  7000  to  18,000  pounds 
per  square  inch;  in  absorption,  from  0.15  to  5.00  per  cent. 

Tests  of  Ohio  Paving-brick. — Table  XXI«  contains  the  re- 
sults of  a  series  of  tests  conducted  by  Prof.  Edward  Orton,  Jr.,  at 
the  solicitation  of  the  Geological  Survey  of  the  State  of  Ohio.  The 
tests  were  performed  with  the  greatest  care  and  absolutely  without 
interest  or  bias  of  any  kind,  and  the  results  are  solely  on  the 
merits  of  the  samples  furnished.  The  tests  are  interesting  and 
valuable  in  several  ways.  It  is  the  first  work  of  the  kind  under- 
taken by  the  State,  and  it  is  also  probably  the  first  large  and  gen- 
eral test  in  which  the  results  could  not  be  attacked  as  being  ex 
parte.  It  is  of  great  interest  to  those  who  compete  for  standing, 
of  course,  and  it  should  be  equally  interesting  to  all  clay-workers 
to  see  so  large  a  list  of  factories,  representing  an  annual  capacity  of 
three  hundred  millions  of  brick,  showing  so  high  an  average 
quality  of  material.  The  samples  were  selected  by  the  manufac- 
turers themselves,  and  therefore  represent  their  best.  It  was  the 
intention  to  make  this  so;  the  public  does  not  desire  to  know  how 
poorly  the  brick-makers  can  do,  but  how  well,  and,  having  shown 
their  ability  to  produce  goods  of  this  quality,  it  should  be  their 
constant  endeavor  to  hold  their  average  output  up  to  the  same 
high  grade. 


MATERIALS   EMPLOYED 


THE   CONSTRUCTION   OF    PAVEMENTS.     8 


TABLE   XXI. 

TESTS  OP  PAVING  BRICKS  MADE  AT  THE  LABORATORY  OF  LATHBURY  & 
SPACKMANN,  IN  PHILADELPHIA,  IN  ACCORDANCE  WITH  THE  REQUIRE- 
MENTS OF  THE  SPECIFICATIONS  OF  THE  NATIONAL  BRICK  MANUFAC- 
TURERS' ASSOCIATION. 


Catskill  Shale 
Paving  Bricks 

from 

Canal  Street, 
July  26, 1897. 


Canton  Shale 
'  Red  Granite  " 
Bricks  from 
Jefferson  Street, 
July  26,  1897. 


Corning  Shale 
Paviug  Bricks 

from 

Second  Street, 
Sept.  6,  1897. 


Average  size,  in  inches 

Average  weight,  in  pounds 

Average  area  of  top  surface,  sq.  in. ... 
Average  volume  of  one  brick,  cu.  in.. 
Average  specific  gravity 


.50X4.00X2.50 

7.46 
21.25 
85.00 

2.38 


8.50X4.00X2.50 

6.99 
21.25 
85.00 

2.45 


8.06X3.91X2.47 

6.69 
20.0 
78.0 

2.63 


Absorption  of  water,  average  of  5: 
Weight  in  Ibs.  after  drying  48  hours  . . 
Weight  in  Ibs.  after  immersion  48  hrs. 

Weight  in  Ibs.  of  water  absorbed 

Percentage  of  water  absorbed 


18.00 
18.89 
0.89 
4.9 


15.78 
16.61 
0.83 
5.26 


17.95 
18.65 
0.70 
3.9 


Cross-breaking  strength,  bricks  on 
edge.  Centre  load  between  supports 
6  inches  apart : 

First 

Second 

Third  

Fourth 

Fifth 

Sixth 

Seventh 

Eighth 

Ninth 

Tenth 


6,840 
8,610 
8,850 
8,510 
8,950 
9,940 
9,120 
11,470 
11,620 
13,210 


8,120 
8,570 
8,950 
9,080 
9,490 
10,270 
11,120 
11,330 
11,690 
12,930 


3,810 
6,380 
6,390 
6,660 


8,510 
9,260 
12,450 
12,460 


Average  strength  in  Ibs. 
Modulus  of  rupture 


9,712  ±  1,778 
2,185  ±     400 


10,155  ±  1,486 
2,285  ±     334 


8,112  ±  2,605 
1,934  ±    .  051 


Impact  tests  (two),  28-inch  rattler,  20 
inches  long,  making  30  revolutions 
per  minute: 


Weight  before  test,  Ibs 

Weight  after  300  revolutions 
Weight  after  1,800  revolutions 
Loss  in  Ibs.  after  300  revolutions 

Loss  in  Ibs.  after  1,800  revolutions 

Loss  per  cent  after  300  revolutions  . . . 
Loss  per  cent  after  1,800  revolutions  .. 


Average  per  cent  after  1,800  revol. 


(1) 

153.37 

146.96 

123.34 

6.41 


4.11 
19.57 


20.7 


18.3 


(2) 

153.56 
141.93 
125.75 

11.63 

27.81 
7.57 

18.11 


.84 


88 


HIGHWAY    CONSTRUCTION. 


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"MATERIALS   EMPLOYED   IN   THE    CONSTRUCTION    OF    PAVEMENTS.     91 


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HIGHWAY   CONSTRUCTION". 


120.  Wood. — Both  the  hard  and  soft  varieties  of  wood  have 
been  employed  for  paving.  In  the  United  States,  cedar  and  cypress, 
on  account  of  their  abundance  and  cheapness,  are  more  generally 
used.  Recently  mesquite,  which  grows  in  abundance  in  both  Texas 
and  Mexico,  has  been  used.  In  Europe  nearly  all  varieties  of  the 

TABLE  XXII. 

SPECIFIC  GRAVITY,  WEIGHT,  AND  RESISTANCE  TO  CRUSHING  OP  VARIOUS 

WOODS. 


Specific 
Gravity. 

Average  Weight, 
pounds  per 
cubic  foot. 

Resistance  to 
Crushing,  pounds, 
per  square  inch. 

Acacia     . 

71  to  .  79 

44 

16000 

Ash   American  white  dry  

.61 

38 

8,900 

Beech 

69 

43 

7  700 

Cedar  American  white  

36 

22  45 

4400 

Chestnut      "          

.46 

22.80 

5  300 

Chestuut                                      .  . 

60 

38 

Cypress  American  

408 

24  4 

6000 

689 

43 

5850 

Ebony  

1.187 

74 

19,000 

Elm  

56 

35 

Fir  American  (Pacific  region). 

405 

25.28 

Fir  European 

512 

32 

6  500 

Hemlock,  Am.  (Atlantic  region) 

.409 
.85 

25.5 
53 

5,300 

.L/ifiruiim  vitflB 

1  33 

83 

10  000 

Mahogany  Spanish     

85 

53 

8  200 

'  '           Honduras  

56 

35 

8000 

.79 

49 

Mesquite,  American  (Texas).  .  .  . 
Oak                 "  white  (Atlantic) 
"  chestnut     " 
«  red 

"  black 

.756 
.763 
.711 
.751 

.687 

.777 

47 
46.5 
44 
46.7 
43.8 
48 

10,450 

7,000 
7,500 
7,000 
7,000 
6  400 

.934 

58 

10,000 

P  ue  American  white  

35  to    45 

21  to  25 

5  400 

red  

'            "           yellow  (Pacific) 
4            '•           pitch  (Atlantic) 
'     Dautzic  

.485 
.530 
.632 
.649 

30 
33 
39 
40 

6,300 
12,000 
5,000 
5,400 

Redwood,  American  (California) 
Spruce,                        (Atlantic).. 

.473 

.408 

29.5 
25.4 

9,500 
5,700 

pine  species  have  been  tried,  as  well  as  oak,  ash,  and  elm,  but  Memel 
and  Dantzic  fir  appears  to  be  the  favorite. 

Recently  jarraJi  from  Australia  and  pyingado  (xylia  dolalri- 


MATERIALS   EMPLOYED   IK   THE   COtfSTKUCTION   OF   PAVEMENTS.     93 


fortnis)  from  India  have  been  introduced  in  London;  the  result? 
are  still  indefinite. 

121.  Whichever  kind  is  used,  it  should  be  sound,  close-grained, 
uniform  in  quality,  free  from  knots  and  sap  and  from  the  bine 
tinge  which  is  a  sign  of  incipient  decay.  All  sappy  wood  should 
be  rejected. 

TABLE  XXIII. 

ABSORPTIVE  POWER  OF  WOOD. 
(E.  R.  ANDREWS  in  "  Engineering  News.") 


Percentage  of  Water  absorbed. 

Dry  Wood. 

Creosoted. 

1.0000 
.7140 
.2000 
.1754to  .8333 

.1600 
.4300 
.4722 

.1250 
.3470 
.0625 
.0236  to  .0306 

.0000 
.1240 
.0000 

Oak                    .               

Spruce  c  

"     (Burnettized  .  2500)  

Hard  pine     .       .  .     '         ... 

White  birch  

122.  The  use  of  creosote  or  other  preserving  processes  makes  it 
difficult  to  discover  defects  in  the  wood,  and  on  this  account  is 
objectionable.     It  is  doubtful  if  creosoting,  etc.,  adds  to  the  life  of 
wood  employed  for  paving. 

123.  Sand, — Sand  is  an  aggregation  of  loose  incoherent  grains 
crystalline  in  structure  and  angular  in  shape,  of  silicious,  argilla- 
ceous, calcareous,  or  other  material,  derived  from  the  disintegration 
of  rocks  or   other   mineral   matter,  and  unmixed  with  earth  or 
organic  matter.     For  road  purposes  the  grains  should  not  exceed 
one  eighth  of  an  inch  in  size. 

124.  The  principal  use  of  sand  is  as  a  foundation  for  broken 
stone,  a  cushion  and  bed  for  stone  paving-blocks,  and  as  a  joint  fill- 
ing.    For  these  purposes  it  is  eminently  suitable,  because  when 
confined  so  that  it  cannot  escape  or  spread  it  possesses  the  valuable 
properties  of  incompressibility,  and  mobility  or  the  quality  of  as- 
suming a  new  position  when  any  portion  of  it  is  disturbed. 

As  a  base  or  cushion  for  blocks  it  quickly  adjusts  itself  to  every 
irregularity  of  their  inferior  surfaces,  and  when  the  blocks  finally 


94  HIGHWAY   CONSTRUCTION. 

settle  in  place  it  furnishes  a  solid  incompressible  medium  to  trans- 
fer the  pressure  to  the  foundation  below.  For  this  purpose  it  should 
be  fine  and  dry;  if  coarse  and  damp,  the  blocks  will  adjust  them- 
selves with  difficulty  and  the  fewer  will  be  the  points  of  support 
between  them  and  the  foundation,  and  the  greater  will  be  the 
pressure  of  contact  and  liability  to  unequal  settlement. 

125.  Sharp  sand,  i.e.,  sand  with  angular  grains,  is  much  better 
than  that  with  rounded  grains,  although  it  is  often  difficult  to 
obtain.     The  sharpness  of  sand  can  be  determined  approximately 
by  rubbing  a  few  grains  in  the  hand  or  by  crushing  it  near  the  ear 
and  noting  if  a  grating  sound  is  produced. 

126.  The  sand  for  bedding  blocks  and  jointing  should  be  clean, 
i.e.,  free  from  loam  or  clay.     The  cleanness  may  be  tested  by  rub- 
bing a  little  of  the  dry  sand  in  the  palm  of  the  hand  and,  after 
throwing  it  out,  noticing  the  atnount  of  dust  left  on  the  hand.     The 
cleanness  of  sand  may  also  be  judged  by  pressing  it  together  be- 
tween the  fingers  while  it  is  damp;  if  the  sand  is  clean,  it  will  not 
stick  together,  but  immediately  fall  apart  when  the  pressure  is 
removed. 

127.  For  concrete  used  for  foundation  it  is  not  necessary  that 
the  sand  should  be  free  from  clay;  indeed  a  small  amount  of  clay 
may  be  beneficial.     Clay  when  dissolved  or  finely  pulverized  con- 
sists of  an  almost  impalpable  powder,  and  when  mixed  with  sand 
its  particles  occupy  the  interstices  between  the  particles  of  cement 
and  sand,  and  are  also  completely  enveloped  by  the  cementing  paste. 
Clay,  dissolved  or  finely  pulverized,  mixed  with  cement  up  to  the 
proportion  of  1  to  1,  appears  to  affect  the  strength  essentially  the 
same  as  an  equal  quantity  of  sand,  and  the  mortar  is  much  more 
dense,  plastic,  and  water-tight.     Such  mortar  is  not  affected  by  the 
presence  of  water. 

The  voids   of  ordinary   sand  average  from  0.3  to  0.5  of  the 
volume;  the  more  uneven  the  sizes  the  smaller  the  voids. 

128.  The  quantity  of  sand  required  for  bedding  paving-blocks 
is  about  one  cubic  yard  to  six  square  yards  of  paving. 

129.  The  price  of  sand  varies  from  40  cents  to  $1.60  per  yard, 
according  to  locality. 

130.  Sand  is  sometimes  sold  by  the  ton.     It  weighs  when  dry 


MATERIALS    EMPLOYED    IN"   THE    CONSTRUCTION    OF    PAVEMENTS.     95 

from  80  to  115  pounds  per  cubic  foot,  or  about  1  to  1|  tons  per 
cubic  yard. 

131.  Gravel  is  an  accumulation  of  small  stones  which  vary  in 
size  from  a  small  pea  to  a  walnut  or  something  larger.  It  is  often 
intermixed  with  other  substances,  such  as  sand,  clay,  loam,  etc., 
from  each  of  which  it  derives  a  distinctive  name.  In  selecting 
gravel  for  road  purposes  the  chief  quality  to  be  sought  for  is  the 
property  of  binding  (see  Art.  424). 

Gravel  in  general  is  unserviceable  for  road-making.  This  is 
due  mainly  to  the  fact  that  the  surface  of  the  pebbles  is  smooth, 
so  that  they  will  not  bind  together  in  the  manner  of  broken  stone. 
There  is  also  an  absence  of  dust  or  other  material  to  serve  as  a 
binder,  and  even  if  such  binding  material  is  furnished  it  is  diffi- 
cult to  effectively  hold  the  rounded  and  polished  surfaces  of  the 
pebbles  together. 

In  certain  deposits  of  gravel,  particularly  where  the  pebbly 
matter  is  to  a  greater  or  less  extent  composed  of  limestone,  a  con- 
siderable amount  of  iron  oxide  has  been  gathered  in  the  mass. 
This  effect  is  due  to  the  tendency  of  water  which  contains  iron  to 
lay  down  that  substance  and  to  take  lime  in  its  place  when  the 
opportunity  for  so  doing  occurs.  Such  gravels  are  termed  ferru- 
ginous. They  are  commonly  found  in  a  somewhat  cemented  state, 
and  when  broken  up  and  placed  upon  roads  they  again  cement, 
even  more  firmly  than  in  the  original  state,  often  forming  a  road- 
way of  very  good  quality. 

The  gravel  found  in  western  Kentucky  and  known  in  com- 
merce as  Paducah  gravel  is  of  this  variety  and  is  extensively  used 
for  road-making. 

"  The  so-called  Tomkins  Cove  gravel,  which  is  much  used  about 
New  York,  is  a  broken  limestone,  apparently  of  the  cement  series. 
It  is  usually  spread  over  the  road,  and  compacted  by  the  traffic. 
The  darker-colored  stone  is  very  pleasant  to  the  eye,  and  it  readily 
makes  a  smooth  wheelway  singularly  free  from  either  mud  or  dust 
even  when  subjected  to  rather  heavy  traffic,  though  it  is  too  friable 
for  economical  use  in  such  situations.  Its  performance  is  so  differ- 
ent from  that  of  the  ordinary  limestones  that  an  analysis  is  ap- 
pended : 


96  HIGHWAY    CONSTRUCTION. 

Lime 60.20  percent 

Alumina , 11.22 

Silica    6.13 

Magnesia 10.45        " 

Carbonic  acid 8.00        " 

Water...  4.00 


100.00  per  cent 

132.  Shingle  is  the  gravel  or  accumulation  of  small  stones 
found  on  the  shores  of  rivers  or  the  sea. 

132a.  Chert  is  a  silicious  material  approaching  the  character 
of  flint;  it  is  composed  of  lime,  silica,  iron  and  alumina,  its  ap- 
pearance varies  from  that  of  limestone  to  sand-stone;  in  color  it 
ranges  from  pure  white  to  milky  blue,  in  texture  from  porous  to 
flinty.  The  name  chert  is  also  frequently  applied  to  the  slag 
derived  from  blast  furnaces. 


MATERIALS   EMPLOYED   IN   THE   CONSTRUCTION   OF   PAVEMENTS.     97 

TABLE   XXIV. 

SPECIFIC  GRAVITY,  WEIGHT,  AND  RESISTANCE  TO  CRUSHING  OP  VARIOUS 

SUBSTANCES. 


Substance. 

Specific 
Gravity. 

Weight, 
pounds  per 
cubic  foot. 

Resistance 
to  Crushing, 
Ibs.  persq.  in. 

Asphaltum          .  .            905  to  1  65 

1  277 

80  to  87.3 

Basalt  (greenstone) 

2  9 

181 

17200 

"      Scotch  

2  95 

184 

8,300 

Bitumen  liquid                                

848 

53 

2  25 

156 

J3rick   best  pressed             ... 

2.4 

150 

14.973 

"       common  hard                                             .  ... 

1  6  to  2 

125 

12,000 

'*       soft  inferior  

1.4 

100 

600  to  3,000 

"       Stourbridge  fire          

2.2 

137 

1.717 

9,000  to  15  000 

1  8 

112  5 

•Chalk 

2.5 

156 

501 

day 

1  8  to  2  1 

119 

63 

"  with  gravel 

2  48 

155 

56  60 

"         English  Portland              .             

1.6  to  1.76 

81  to  102 

"          French        " 

76  to  88 

1  6 

100 

Concrete  ordinary 

1  9 

119 

2  2 

137 

1  28  to  2 

72  to  80 

"      common  loam  perfectly  dry  shaken 

82  "  92 

Earth,  common  loam,  perfectly  dry,  moderately 
rammed 

90       100 

70       76 

66       68 

"               "           "          "          "      shaken.   ... 

75       90 

"              "           "     as  a  soft  flowing  mud 

90       100 
104       112 

Earth,  common  loam  as  a  soft  flowing  mud  well 
pressed  into  a  box  

110  "  120 

Flint 

2  6 

126 

2  5  to  2  8 

166 

Glass             ....                                 .          

2  5  to  3.45 

186 

27,000-30,000 

Gneiss 

2  69 

168 

96 

2  8 

175 

100 

(run-powder,  loose      

.900 

56.25 

1  000 

62  5 

7  21 

450 

110,000 

•'     wrought                     .                    

7.69 

485 

45,000 

Ice 

917  to   922 

57  4 

Lead  

11.  30  to  11.  47 

709.6 

6,944-7,780 

1  5 

95 

53 

64 

75 

165 

*  iak  onrj  or  gi  aniie  or  *""®>-        e  "  essea..  .         . 

154 

of  dry  rubble  

138 

of  sandst'  >ne  dressed  
of  brickwork,  close  joints  



144 
140 



medium  quality  
"          soft  bricks  
Mica  

2  75  to  3.1 

1  38  to  1  9 

196 

100 
183 
106 

Mud,  dry,  close  
wet.  moderately  pressed  
''      wet,  fluid  
.Naphtha                                              

1.63 

.848 

80  to  110 
110  "  130 
104  "  120 
52.9 

98 


HIGHWAY   CONSTRUCTION. 


TABLE   XXIV.— Continued. 

SPECIFIC  GRAVITY,  WEIGHT,  AND   RESISTANCE  TO  CRUSHING  OF  VARIOUS 

SUBSTANCES. 


Substance. 

Specific 
Gravity. 

Weight, 
pounds  pei- 
cubic  foot. 

Resistance 
to  Crushing, 
Ibs.  persq.  in. 

Petroleum  

878 

54  8 

Peat  dry  unpressed    ...  . 

20  to  30 

1  15 

69 

Porphyry    

2  66  to  2  8 

170 

Quartz,  pure  

2  65 

165 

'*       finely  pulverized,  loose  

90 

u             "             "           shaken  .   . 

105 

"            "          packed  

112 

"       quarried,  loose  .              .... 

94 

2  75 

90  to  106 

"     "         "        perfectly  wet  

118  "  129 

river 

1  88 

117 

pit,  coarse  

1  61 

100 

••    fine          

1  52 

95 

(Thames)  England  

1  64 

102 

Serpentines  ..          ....        

2  5  to  2  6 

162 

Shales  red  or  black 

2  6 

162 

*'     quarried  in  piles  

92 

Shingle     

1  42 

88 

Slate  

2  7  to  2  9 

175 

10  000-21  000' 

Soapstone  or  steatite  .... 

1  73 

170 

Steel 

7  85 

490 

336  000 

Snow,  freshly  fallen  

5  to  12 

"      compacted          

15  "  20 

* 

Water,  pure  rain,  or  distilled  at  32°  Fah.,  barom. 
30  inches  

62  417 

Water,  pure  rain,  or  distilled  at  62°  Fah.,  barom. 
30  inches  

1  00 

62  355 

Water,  pure  rain,  or  distilled  at  212°  Fah.,  barom. 
30  inches 

59  7 

Water,  sea  1  026  to  1  030 

1  028 

64  08 

CHAPTEK  III. 
STONE  PAVEMENTS. 

133.  Stone  Pavements. — Stone  in  a  variety  of  forms  has  been 
employed  as  a  paving  material  for  more  than  2500  years.     The 
Romans  used  it  in  the  form  of  large,  irregularly-shaped  blocks  laid 
on  a  massive  foundation  of  concrete.     In  this  form  it  is  unsurpassed 
in  regard  to  solidity  and  durability,  but  it  is  objectionable  for 
modern  traffic.     The  surface  of  the  large  blocks  wears  smooth,  and 
hence  affords  but  an  uncertain  foothold  for  horses.     These  large 
blocks  were  superseded  by  round  pebbles  or  cobblestones,  obtained 
from  the  beach  and  gravel-pits.     This  class  of  pavement  has  been 
used  extensively  in  the  United  States.     It  is  recorded  that  Boston, 
Mass.,  in  1663  had  many  streets  paved  with  pebbles.     In  1718 
cobblestone  pavements  were  introduced  into  Philadelphia,  and  this 
city  is  the  only  one  to  retain  them  on  a  large  scale  at  the  present 
day. 

134.  Cobblestone    Pavement. — Cobblestones    bedded    in    sand 
possess  the  merit  of  cheapness   and   afford  an  excellent  foothold 
for   horses,  but   the   roughness   of   such  pavements  requires  the 
expenditure  of  a  large  amount  of  tractive  energy  to  move  a  load 
over  them.     Aside  from  this,  cobblestones  are  entirely  wanting  in 
the  essential  requisites  of  a  good  pavement.     The  stones  being  of 
irregular  size,  it  is  almost  impossible  to  form  a  bond  or  hold  them 
in  place.     Under  the  action  of  the  traffic  and  frost  the  roadway 
soon  becomes  a  mass  of  loose  stones.     Moreover,  cobblestone  pave- 
ments are  difficult  to  keep  clean,  and  very  unpleasant  to  travel 
over. 

135.  Specifications  for  Cobblestone  Pavement. — The  following  is 
the  common  form  of  specification  for  this  class  of  pavement: 

Stone. — The  stones  are  to  be  the  best  selected  water  or  bank 

paving-stones,  of  a  durable  and  uniform  quality. 

99 


100 


HIGHWAY   CONSTRUCTION". 


TYPES  OF  STONE  PAVEMENTS 


FIG.  1.     ROMAN, 


FIG,  2,    COBBLESTONE, 


FIG,  3.    BELGIAN    BLOCK, 


FIG,  4.   EARLY  GRANITE  BLOCK, 


STONE    PAVEMENTS.  101 


Size  of  Stone. — No  stone  shall  be  less  than  four  (4)  inches  nor 
more  than  eight  (8)  inches  in  any  direction  on  the  surface.  No 
triangular  or  split  stone  will  be  allowed.  All  stones  shall  be  set 
perpendicular  and  on  their  small  ends,  the  large  stones  to  be  placed 
on  the  sides  of  the  street,  and  the  small  ones  in  the  center. 

Foundation  and  Laying. — The  pavement  shall  be  laid  on  a 
bed  of  good  sharp  sand  or  fine  gravel,  at  least  ten  (10)  inches  in 
depth,  except  where  clay  or  a  similar  substance  is  met  with,  when 
the  sand  must  be  eighteen  (18)  inches  deep.  The  bed  of  sand  or 
gravel  shall  be  laid  ready  for  the  pavement  at  least  thirty  (30)  feet 
in  advance  of  the  pavement.  The  stones  after  being  set  in  position 
must  be  rammed  with  a  heavy  rammer  until  they  are  firmly  settled 
in  their  beds.  After  the  pavement  is  rammed  a  layer  of  sand  or 
gravel  two  (2)  inches  thick  is  spread  over  it  and  left  to  work  its 
way  in  between  the  stones. 

In  consequence  of  the  many  defects  of  this  class  of  paving  its 
construction  has  been  practically  abandoned,  but  large  areas  still 
remain,  which  are  being  gradually  removed. 

136.  Belgian  Block  Pavement. — Cobblestones  were  displaced  by 
pavements  formed  of  small  cubical  blocks  of  stone.     This  type  of 
pavement  was  first  laid  in  Brussels,  thence  imported  to  Paris,  and 
from  there  to  the  United  States,  where  it  has  been  widely  known 
as  the  "  Belgian  block"  pavement.     It  has  been  largely  used  in  New 
York  City,  Brooklyn,  and  neighboring  towns,  the  material  being 
trap-rock  obtained  from  the  Palisades  on  the  Hudson  River. 

137.  The  stones  being  of  regular  shape  remain  in  place  better 
than  the  cobblestones,  but  the  cubical  form  (usually  five  inches)  is 
a  mistake.     The  foothold  is'  bad,  the  stones  wear  round,  and  the 
number  of  joints  is  so  great  that  ruts  and  hollows  are  quickly 
formed.     This   pavement   offers   less  resistance   to  traction  than 
cobblestones,  but  it  is  rough  and  noisy. 

138.  Specification  for  Belgian  Block  Pavement.— The  following 
is  the  common  form  of  specifications  for  the  Belgian  block : 

Stone. — The  stones  are  to  be  obtained  from  the  trap  or  other 
durable  rocks. 

Size  of  Stones.— Each  block  shall  measure  not  less  than  five 
(5)  inches  nor  more  than  seven  (7)  inches  in  length;  nor  less  than 
five  (5)  inches  nor  more  than  six  (6)  inches  in  width;  in  depth  not 
less  than  six  (6)  inches  nor  more  than  seven  (7)  inches;  nor  shall 


102  HIGHWAY   CONSTRUCTION 

the  difference  between  the  base  and  the  top  surface  of  any  block 
exceed  one  inch  in  either  direction. 

139.  The  blocks  are  laid  upon  a  foundation  of  sand  six  inches 
thick,  in  parallel  courses,  perpendicular  to  the  axis  of  the  street. 
When  so  laid  the  blocks  are  thoroughly  rammed  to  the  required 
grade   and   cross-section.     No    ramming   should   be   done   within 
twenty-five  feet  of  the  work  that  is  being  laid.     After  ramming  the 
surface  is  covered  with  a  coat  of  clean  sand  which  is  broomed  into 
the  joints. 

140.  Granite  Block  Pavement. — The  Belgian  block  has  been 
gradually  displaced  by  the  introduction  of  rectangular  blocks  of 
granite.     Blocks  of  comparatively  large  dimensions  were  at  first 
employed.     They  were  from  6  to  8  inches  in  width  on  the  surface, 
by  from   10  to  20  inches   in   length,  with  a  depth  of  9  inches. 
They  were  merely  placed   in  rows  on  the  subsoil,  perfunctorily 
rammed,  the  joints  filled  with  sand,  and  the  street  thrown  open 
to  traffic.     The  unequal  settlement  of  the  blocks,  the  insufficiency 
of  the  foothold,  and  the  difficulty  of  cleansing  them  led  to  the 
gradual  development  of  the  latest  type  of  stone-block  pavements, 
which  consists  of  narrow  rectangular  blocks  of  granite,  properly 
proportioned,   laid  on  an  unyielding  and  impervious   foundation, 
with  the  joints  between  the  blocks  filled  with  an  impermeable 
cement.     This  type  is  practically  a  return  to  the  system  of  the 
Komans,  but  with  blocks  of  lesser  dimensions  than  they  used. 

141.  Experience  has  proved  beyond  doubt  that  this  latter  type 
of  pavement  is  the  most  enduring  and  economical  for  roadways 
subjected  to  heavy  and  constant  traffic.     Its  advantages  are  many, 
while  its  defects  are  few. 

142.  Advantages. 

(1)  Adaptability  to  all  grades. 

(2)  Suits  all  classes  of  traffic. 

(3)  Exceedingly  durable. 

(4)  Foothold,  fair. 

(5)  Requires  but  little  repair. 

(6)  Yields  but  little  dust  or  mud. 

(7)  Facility  for  cleansing,  fair. 

143.  Defects. — (1)  Under  certain  conditions  of  the  atmosphere 
its  surf  ace.  becomes  greasy  and  slippery. 

(2)  The  incessant  din  and  clatter  occasioned  by  the  movement 


STONE   PAVEMENTS. 


103 


IMPROVED  GRANITE-BLOCK  PAVEMENT. 


GUTTER  FORMED  OF 
3  ROWS  OF  BLOCKS 
LONGITUDINALLY. 


URB5"WIDE 
AND  18"  DEER 


i. 5.  CROSS   SECTION. 


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^'S*:5t^^5^T  j^T :"  ''tt&jM*  <+*%  i^a-j+v-g  *?%,.? 


FIG.  7.   LONGITUDINAL  SECTION. 


104  HIGHWAY    CONSTRUCTION. 

of  traffic  over  it  is  an  intolerable  nuisance,  and  it  is  claimed  by 
many  physicians  that  the  noise  injuriously  affects  the  nerves  and 
health  of  persons  who  are  obliged  to  live  or  do  business  in  the 
vicinity  of  streets  so  paved. 

(3)  Horses  constantly  employed  upon  it  soon  suffer  from   the 
continual  jarring  produced  in  their  legs  and  hoofs,  and  quickly 
wear  out. 

(4)  The  discomfort  to  persons  riding  over  it  is  very  great  because 
of  the  continual  jolting  to  which  they  are  subjected. 

(5)  If  stones  of  an  unsuitable  quality  are  used,  i.e.,  those  that 
polish,  the  surface  quickly  becomes  slippery  and  exceedingly  unsafe- 
for  travel. 

144.  Quality  of  the  Stone. — The  harder  and  more  durable  rocks 
like  basalt  and  true  granite  are  unsuitable;  they  have  the  fault  of 
wearing  smooth  and  more  or  less  spherical  when  subjected  to  heavy 
traffic,  and  under  certain  conditions  of  the  weather  they  become 
greasy  and  slippery. 

145.  The  less  durable  rocks,  such  as  syenite,  the  granites  in 
which  hornblende  predominates,  and  the  harder  sandstones,  are  the 
most  suitable;  they  do  not  polish  and  afford  a  good  foothold  for 
the  horses.     Where  the  harder  and  more  durable  rocks  have  been 
used,  they  have  caused  dissatisfaction,  and  have  been  removed  before 
they  had  been  down  many  years. 

146.  Size  and  Shape  of  the  Blocks.— The  proper  size  of  the  blocks 
for  paving  purposes  has  been  a  subject  of  much  discussion,  and  a 
great  variety  of  forms  and  dimensions  are  to  be  found  in  all  cities. 

For  stability  a  certain  proportion  must  exist  between  the  depth,, 
the  length,  and  the  breadth.  The  depth  must  be  such  that  when  the 
wheel  of  a  loaded  vehicle  passes  over  one  edge  of  its  upper  surface 
it  will  not  tend  to  tip  up.  The  resultant  direction  of  the  pressure 
of  the  load  and  adjoining  blocks  should  always  tend  to  depress  the 
whole  block  vertically;  where  this  does  not  happen  the  maintenance 
of  a  uniform  surface  is  impossible.  To  fulfil  this  requirement  it  is. 
not  necessary  to  make  the  block  more  than  seven  (7)  inches  deep. 

147.  Width  of  the  Blocks. — The  maximum  width  of  the  blocks 
is  controlled  by  the  size  of  horses'  hoofs.    To  afford  good  foothold  to 
horses  drawing  heavy  loads,  it  is  necessary  that  the  width  of  each 
block  measured  along  the  street  shall  be  the  least  possible  consistent 
with  stability;  if  it  is  large,  a  horse  drawing  a  heavy  load  attempt- 


STONE   PAVEMENTS.  1Q5 


ing  to  find  a  joint  slips  back,  and  requires  an  exceptionally  wide 
joint  to  pull  him  up.  It  is  therefore  desirable  that  the  width  of  a 
block  should  not  exceed  three  (3)  inches,  or  that  four  taken  at 
random  and  placed  side  by  side  will  not  measure  more  than  fourteen. 
(14)  inches. 

148.  Length  of  the  Blocks. — The  length  measured  across  the 
street  must  be  sufficient  to  break  joints  properly,  for  two  or  more 
joints  in  a  line  lead  to  the  formation  of  grooves.     For  this  purpose 
the  length  of  the  block  should  be  not  less  than  nine  (9)  inches  nor 
more  than  twelve  (12)  inches. 

149.  Form  of  the  Blocks.— The  blocks  should  be  well  squared 
and  must  not  taper  in  any  direction;  sides  and  ends  should  be  free 
from   irregular   projections.     Blocks  that  taper  from  the  surface 
downwards  (wedge-shaped)  should  not  be  permitted  in  the  work; 
but  if  any  are  allowed,  they  should  be  set  with  the  widest  side  down. 

150.  Manner  of  Laying  the  Blocks.— The  blocks  should  be  laid 
in  parallel  courses,  with  their  longest  side  at  right  angles  to  the 
axis  of  the  street,  and  the  longitudinal  joints  broken  by  a  lap  of 
at  least  two  inches  (see  Fig.  6).     The  reason  for  this  is  to  prevent 
the  formation  of  longitudinal   ruts,  which   would  happen  if  the 
blocks   were  laid   lengthwise.      Laying  the   blocks  obliquely  and 
"  herring-bone  "  fashion  has  been  tried  in  several  cities  with  the 
idea  that  the  wear   and   formation  of  ruts  would  be  reduced  by 
having  the  vehicles  cross  the  blocks  diagonally.     The  method  has 
failed  to  give  satisfactory  results;  the  wear  was  irregular  and  the 
foothold  defective,  the  difficulty  of  construction  was  increased  by 
reason  of  the  labor  required  to  form  the  triangular  joints,  and  the 
method  was  wasteful  of  material. 

151.  The  gutters  should  be  formed  by  three  or  more  courses  of 
block,  laid  with  their  length  parallel  to  the  curb. 

152.  At  junctions  or  intersections  of  streets  the  blocks  should 
be  laid  diagonally  from  the  centre,  or  "  herring-bone  "  fashion,  as 
shown  in  Fig.  7«.     The  reason  for  this  is  (1)  to  prevent  the  traffic 
crossing  the   intersection  from   following  the   longitudinal  joints 
and  thus  forming  depressions  and  ruts;  (2)  laid  in   this  manner 
they  afford  more  secure  foothold  for  horses  turning  the  corners. 
The  ends  of  the  diagonal   blocks   where   they   abut   against   the 
straight  blocks  must  be  cut  to  the  required  bevel.     The  method  of 
paving  junctions  shown  in  Fig.  76  while  extensively  employed  is 
erroneous  for  the  above  reasons. 


106 


HIGHWAY   CONSTRUCTION. 


STONE    PAVEMENTS. 


107 


3=23 


SECTION  ON  A,  B,  C,  D. 


£c|ROS's'lN|6ST'ONEb  JI2'*6 


FIG,  7B,~!NTERSECTION  PAVED  WITH  GRANITE  BLOCKS. 

153.  The  blocks  forming  each  course  must  be  of  the  same  depth, 
and  no  deviation  greater  than  one  quarter  (i)  of  an  inch  should  be 
permitted.  The  blocks  should  be  assorted  as  they  are  delivered, 
and  only  those  of  corresponding  depth  and  width  should  be  used  in 
the  same  course.  The  better  method  would  be  to  accurately  gauge  the 
blocks  at  the  quarry:  the  cost  would  be  considerably  less;  it  would 
also  avoid  the  inconvenience  to  the  public  by  the  stopping  of  travel 
resulting  from  the  rejection  of  defective  material  on  the  ground. 
This  method  would  undoubtedly  be  preferable  to  the  contractor, 
who  would  be  saved  the  expense  of  handling  unsatisfactory  material, 
and  it  would  also  leave  the  inspectors  free  to  pay  more  attention  to 
the  manner  in  which  the  work  of  paving  is  performed. 


108  HIGHWAY    CONSTRUCTION. 

The  accurate  gauging  of  the  blocks  is  a  matter  of  much  im- 
portance. If  good  work  is  to  be  executed,  the  blocks  when  laid 
must  be  in  parallel  and  even  courses;  and  if  the  blocks  be  not  ac- 
curately gauged  to  one  uniform  size,  the  result  will  be  a  badly  paved 
street  with  the  courses  running  unevenly. 

The  cost  of  assorting  the  blocks  into  lots  of  uniform  width,  after 
delivery  on  the  street,  is  far  in  excess  of  any  additional  price  which 
would  have  to  be  paid  for  the  accurate  gauging  at  the  quarry. 

154.  Foundation. — The  foundation  of  the  blocks  must  be  solid 
and  unyielding,  a  bed  of  hydraulic  cement  concrete  is  the  most 
suitable,  the  thickness  of  which  must  be  regulated  according  to 
the  traffic;  the  thickness,  however,  should  not  be  less  than  four  (4) 
inches  and  need  not  be  more  than  nine  (9)  inches.     A  thickness 
of  six  (6)  inches  will  sustain  a  traffic  of  600  tons  per  foot  of  width. 

155.  Cushion-coat. — Between  the  surface  of  the  concrete  and  the 
base  of  the  blocks  there  must  be  placed  a  cushion-coat  formed  of  an 
incompressible  but  mobile  material,  the  particles  of  which  will 
readily  adjust  themselves  to  the  irregularities  of  the  base  of  the 
blocks  and  transfer  the  pressure  of  the  traffic  uniformly  to  the  con- 
crete below.    A  layer  of  dry,  clean  sand  f  of  an  inch  thick  forms  an 
excellent  cushion-coat.     Its  particles  must  be  of  such  fineness  as  will 
pass  through  a  No.  8  screen ;  if  coarse  and  containing  pebbles,  they 
will  not  adapt  themselves  to  the  irregularities  of  the  base  of  the 
blocks,  hence  the  blocks  will  be  supported  only  at  a  few  points  and 
unequal  settlement  will  take  place  when  the  pavement  is  subjected  to 
the  action  of  traffic.     The  sand  must  also  be  perfectly  free  from 
moisture,  artificial  heat  must  be  used  to  dry  it  if  necessary.     This 
requirement  is  an  absolute  necessity.    There  should  be  no  moisture 
below  the  blocks  when  laid,  nor  should  water  be  allowed  to  penetrate 
below  the  blocks;  if  such  happens,  the  effect  of  frost  will  be  to  up- 
heave the  pavement  and  crack  the  concrete. 

Where  the  best  is  desired  without  regard  to  cost,  a  layer  half 
an  inch  thick  of  asphaltic  cement  may  be  substituted  for  the  sand 
with  superior  and  very  satisfactory  results. 

156.  Laying  the  Blocks. — The  blocks  should  be  laid  stone  to 
stone,  so  that  the  joint  may  be  of  the  least  possible  width;  wide 
joints  cause  increased  wear  and  noise  and  do  not  increase  the  foot- 
hold.    The  courses  should  be  commenced  on  each  side  and  worked 
toward  the  middle,  and  the  last  stone  should  fit  tightly. 


STONE   PAVEMENTS.  109 


157.  Ramming. — After  the  blocks  have  been  set  they  should  be 
well  rammed  down,  and  the  stones  which  sink  below  the  general 
level   should   be  taken   up   and   replaced  with  a  deeper  stone  or 
brought  to  level  by  increasing  the  sand-bedding. 

158.  The  practice  of  workmen  is  invariably  to  use  the  rammer 
so  as  to  secure  a  fair  surface.     This  is  not  the  result  intended  to  be 
secured,  but  to  bring  each  block  to  an  unyielding  bearing.     The 
result  of  such  a  surfacing  process  is  to  produce  an  unsightly  and 
uneven  roadway  when  the  pressure  of  traffic  is  brought  upon  it. 
The  rammer  used  should  not  weigh  less  than  fifty  pounds  and  have 
a  diameter  of  not  less  than  three  inches. 

159.  Joint  -  filling.  —  All   stone -block   pavements   depend  for 
their  water-proof  qualities  upon  the  character  of  the  joint-filling. 
Joints  filled  with  sand  and  gravel  are  of  course  pervious.   A  grout  of 
lime  or  cement  mortar  does  not  make  a  permanently  water-tight 
joint ;  it  becomes  disintegated  under  the  vibration  of  the  traffic.    An 
impervious  joint  can  only  be  made  by  employing  a  filling  made 
from  bituminous  or  asphaltic  material;  this  renders  the  pavement 
more  impervious  to  moisture,  makes  it  less  noisy,  and  adds  con- 
siderably to  its  strength. 

160.  Bituminous  Cement  for  Joint-filling. — The  bituminous  ma- 
terials employed  are  (1)  the  tar  produced  in  the  manufacture  of 
gas,  which,  when  redistilled,  is  called  distillate,  and  is  numbered 
1.  2,  3,  4,  etc.,   according  to  its  density;  this  material  under  the 
name  of  paving-pitch  is  extensively  used  both  alone  and  in  com- 
bination  with  other  bituminous  substances;    (2)  combinations  of 
gas-  or  coal-tar  with  refined  asphaltum;  (3)  mixtures  of  refined 
asphaltum,  creosote,  and  coal-tar. 

The  formula  for  the  bituminoug  joint-filling  used  in  New  York 
City  is: 

Refined  Trinidad  asphaltum 20  parts 

No.  4  coal-tar  distillate 100    ' 

Residuum  of  petroleum 3    ' 

In  Washington,  D.  C.,  coal-tar  distillate  No.  6  is  used  alone. 

In  Europe  a  bituminous  cement  much  used  is  composed  of  coa[- 
tar,  asphaltum,  gas-tar,  and  creosote  oil,  in  the  proportion  of  100 
pounds  of  asphaltum  to  4  gallons  of  tar  and  1  gallon  of  creosote. 
These  proportions  are  varied  somewhat,  according  to  the  quality 
of  the  asphaltum  employed.  The  mixture  is  melted,  and  boiled  from 


HO  HIGHWAY   CONSTRUCTION. 

one  to,  two  hours  in  a  suitable  boiler,  then  poured  into  the  joints 
in  a  boiling  state.  This  mixture  is  impervious  to  moisture,  and 
possesses  a  degree  of  elasticity  sufficient  to  prevent  it  from  cracking. 

161.  The  mode  of  applying  the  bituminous  cement  is  as  follows: 
After  the  blocks  are  rammed  the  joints  are  filled  to  a  depth  of  about 
two  inches  with  clean  gravel  heated  to  a  temperature  of  about  250°' 
F.,  then  the  hot  cement  is  poured  in  until  it  forms  a  layer  of  about 
one  inch  on  top  of  the  gravel,  then  more  gravel  is  filled  in  to  a  depth 
of  about  two  inches,  then  cement  is  poured  in  until  it  appears  on 
top  of  the  gravel,  then  more  gravel  is  added  until  it  reaches  to 
within  half  an  inch  of  the  top  of  the  blocks;  this  remaining  half 
inch  is  filled  with  the  cement,  and  then  fine  gravel  or  sand  is 
sprinkled  over  the  joints. 

In  some  cases  the  joints  are  first  filled  with  the  heated  gravel,, 
then  the  cement  poured  in  until  the  sand  beneath  and  the  gravel 
between  the  blocks  will  absorb  no  more  and  the  joints  are  filled 
flush  with  the  top  of  the  pavement.  This  method  is  open  to  ob- 
jection, for  if  the  gravel  is  not  sufficiently  hot  the  cement  will  be 
chilled,  and  will  not  flow  to  the  bottom  of  the  joint,  but  instead 
will  form  a  thin  layer  near  the  surface,  which,  under  the  action  of 
frost  and  the  vibration  of  traffic,  will  be  quickly  cracked  and  broken 
up,  the  gravel  will  settle  and  the  blocks  will  be  jarred  loose,  and 
the  surface  of  the  pavement  will  become  a  series  of  ridges  and  hol- 
lows. 

The  quantity  of  cement  required  per  square  yard  of  pavement 
will  vary  according  to  the  shape  of  the  blocks,  width  of  the  joints, 
and  depth  of  the  sand-bed ;  with  well-shaped  blocks,  close  joints, 
and  one  half  inch  sand-bed  the  quantity  will  vary  from  3^  to  5 
gallons;  with  ill-shaped  blocks,  wide  joints,  and  heavy  sand-bed  10 
to  12  gallons  would  not  be  an  excessive  amount  to  use  to  secure 
the  result  obtained  by  employing  well-shaped  blocks  and  close 
joints. 

The  cost  of  paving-pitch  is  variable;  it  ranges  from  six  to  ten 
cents  per  gallon. 

A  joint-filling  known  as  "  Murphy's  Grout  Filling"  has  been 
and  is  extensively  used  in  the  Central  States.  This  filling  is  com- 
posed of  Portland  cement,  iron-slag,  and  sand.  It  is  said  to  be 
waterproof,  durable,  and  cheap.  It  can  be  used  with  equal  advan- 
tage for  block,  brick,  cobblestone,  and  macadam  pavements. 


STONE    PAVEMENTS. 


In  manner  of  application  it  differs  but  little  from  that  of  the 
bituminous  cement.  It  is  mixed  in  a  portable  box,  and  when  of  a 
good  flowing  (but  not  liquid)  consistency  it  is  thrown  upon  the 
pavement  with  shovels  and  swept  into  the  joints  with  steel  brooms, 
and  after  forty-eight  hours  it  is  set  and  the  pavement  is  ready  for 
traffic. 

162.  Sandstone-block  Pavements.— Block  pavements  formed  of 
Medina  and  Berea  sandstones  are  used  in  several  of  the  Lake  cities, 
While  not  as  lasting  as  granite,  the  sandstone  is  very  durable,  is 
less  noisy,  and  does  not  become  polished  or  slippery  under  traffic, 
wears  evenly,  and  is  adapted  to  all  classes  of  traffic. 

163.  The  best  examples  of  this  kind  of  pavement  are  found  in 
Buffalo,  N.  Y.,  where  two   classes   are  used.    For  first  class  the 
specifications  call  for  a  foundation  of  six  inches  of  concrete  with  a 
three-inch  cushion  of  aand.     The  blocks  are  of  dressed  stone,  four 
inches  wide,  seven  inches  deep,  and  not  less  than  eight  inches  long. 
The  joints  are  filled  with  bituminous  cement.     For  the  second 
class  the  blocks  are  of  irregular  size  laid  on  a  foundation  of  ten  to 
eighteen  inches  of  sand,  depending  upon  the  character  of  the  sub- 
soil, the  joints  are  filled  with  sand." 

164.  The  cost  of  first-class  Medina  in  Buffalo  is  $4  per  square 
yard;    Cleveland,  $3.50;   Columbus,  with  a   10-inch  broken-stone 
foundation,  $3.25.     Second-class  average  $1.75,  and  with  asphalt 
filling  cost  36  cents  per  yard  more. 

165.  Limestone-block  Pavements. — Limestone  block  was  tried 
in  Kansas  City  on  a  concrete  foundation,  but  being  set  on  edge  it 
wore  unevenly,  and  in  a  year  or  two  was  shivered  and  split  by  the 
frost.     This  is  the  universal  experience  of  all  cities  using  limestone 
blocks. 

166.  Pavements  on  Steep  Grades. — Stone  blocks  may  be  em- 
ployed on  all  practicable   grades,  but   on   grades   exceeding   10# 
cobblestones  afford  a  better  foothold   than   blocks.     The  cobble- 
stones should  be  of   a  uniform  length,  the  length  being  at  least 
twice  the  breadth,  say  stones  6  inches  long  and  2£  to  3  inches  in 
diameter.     These  should    be   set   on   a  concrete  foundation,  laid 
stone  to  stone,  and  the  interstices  filled  with   cement  grout  or 
bituminous   cement;    or   a   bituminous   concrete  foundation   may 
be  employed  and  the  interstices  between  the  stones   filled  with 


112 


HIGHWAY    CONSTRUCTION". 


STONE  PAVEMENTS  ON  GRADES. 


FIG.  8.    COBBLE  ON  CONCRETE, 


FIG,  9,    GRANITE  BLOCKS-STEPPED, 


FIG,  10.    GRANITE   BLOCKS-WIDE  JOINTS, 


STO.NE   PAVEMENTS. 


asphaltic  paving-cement.  Should  stone  blocks  be  preferred,  they 
must  be  laid,  when  the  grade  exceeds  5#,  with  a  serrated  surface  by 
either  of  the  methods  shown  in  Figs.  9  and  10.  The  method 
-shown  in  Fig.  9  consists  in  slightly  tilting  the  blocks  on  their  bed 
so  as  to  form  a  series  of  ledges  or  steps,  against  which  the  horses' 
feet  being  planted,  a  secure  foothold  is  obtained.  The  method 
shown  in  Fig.  10  consist  in  placing  between  the  rows  of  stones  a 
course  of  slate,  or  strips  of  creosoted  wood,  rather  less  than  one 
inch  in  thickness  and  about  an  inch  less  in  depth  than  the  blocks; 
or  the  blocks  may  be  spaced  about  one  inch  apart,  and  the  joints 
filled  with  a  grout  composed  of  gravel  and  cement.  The  pebbles 
of  the  gravel  should  vary  in  size  between  one  quarter  and  three 
quarters  of  an  inch. 

167.  Durability  of  Granite  Blocks. — The  average  life  or  dura- 
bility of  granite  blocks  under  heavy  traffic  may  be  taken  at  fifteen 
years;  but  since  the  nature  of  the  traffic,  the  state  of  cleanliness 
and  other  conditions  must  be  taken  into  account  when  inquiring 
into  the  durability,  it  follows  that  in  no  two  streets  is  the  endur- 
ance or  the  cost  the  same,  and  the  difference  between  the  highest 
and  the  lowest  period  of  endurance  and  amount  of  cost  is  very 
considerable.     The    practice   followed    almost    uniformly  in    the 
English  cities  is  to  remove  the  worn  blocks,  re-dress  them  and 
relay   them    in    other    and    secondary   thoroughfares.     Thus  the 
duration   or   life   of  the   blocks   may  be   doubled   or  more   than 
doubled.     Indeed,  with  the  exception  of  the  portion  worn  off  by 
the  friction  of  the  traffic,  not  a  fragment  of  granite  paving  may  be 
said  to  be  lost.     After  passing  its  first  years  in  a  leading  thorough- 
fare it  goes  into  a  secondary  thoroughfare  until  completely  worn 
down  and  rounded,  and  will  even  then  command  a  price  of  from 
30  to  60  cents  per  square   yard.     Not   even  a  fragment  that  is 
knocked  off  the  component  stones  when  undergoing  the  operation 
of  being  dressed  into  shape  is  lost,  as  it  is  made  available  either  for 
macadamizing  or  for  concrete  to  form  the  foundation   of  other 
pavements.     "  In  truth  granite  can  only  be  said  to  be  worn  out 
when  it  has  been  broken  up  for  macadamization  and  then  crushed 
into  powder  by  the  vehicles." 

168.  Wear  of  Granite  Blocks.— Stones  from  different  quarries 
3,nd  even  from  the  same  quarry  will  show  considerable  variation  in 
the  amount  worn  away  in   a  given   time  under  exactly  similar 
•conditions.     Therefore  no  statement  of  wear  can  be  given  which 


114  HIGHWAY    CONSTRUCTION. 

will  be  applicable  to  all  varieties  of  stones.  On  London  bridge,, 
which  has  a  traffic  of  over  15,000  vehicles  in  12  hours,  the  wear 
of  granite  blocks  has  been  found  to  be  at  the  rate  of  .222  inch  per 
year,  or  the  number  of  years  required  to  wear  away  one  inch  is, 
four  and  one  half. 

TABLE  XXV. 

WEAR  AND  DURATION  OF  ABERDEEN  GRANITE  PAVEMENTS  IN  THE  CITY  OF 
LONDON.    BLOCKS  3  INCHES  WIDE,  9  INCHES  DEEP. 


Aberdeen  Granite  Pavements. 


Vertical  Wear.        Duration. 
Inches.  Years. 


Vertical  wear  per  100  vehicles  in  12  hours, 

per  foot  of  width  per  year ^                       1 

Total  vertical  wear  in  principal  streets 2                     15 

Total  additional  wear  in  minor  streets 2                     20 

Total  vertical  wear  when  laid  aside 4                     35 

Remaining  depth  when  laid  aside 5 

Depth  of  new  blocks 9 

ID  Liverpool,  under  a  traffic  of  216,570  tons  per  yard  of  width 
pei  annum,  the  wear  was  not  measurable. 

169,  Cost  of  Maintaining  Granite-block  Pavements. — As  to  the- 
durability  and   cost   of  maintaining  granite-block  pavements  in 
America  no  satisfactory  statistics  can  be  obtained. 

The  annual  cost  of  maintenance  in  London  varies  from  six  to- 
il ineteen  cents  per  square  yard,  depending  upon  the  traffic.  In 
Liverpool  repairing  costs  four  cents  per  annum,  and  cleaning  and 
sprinkling  fourteen  cents.  In  London  the  cost  of  maintenance,, 
including  interest,  etc.,  on  first  cost  is  from  25  to  69  cents  per 
square  yard  per  annum.  In  St.  Louis,  Mo.,  maintenance  costs 
from  £  to  2 1  cents  per  annum. 

The  average  cost  of  maintaining  granite-block  pavements  in 
the  United  States,  irrespective  of  traffic  tonnage,  and  exclusive 
of  cleaning  and  sprinkling,  appears  to  be  about  1^  cents  per  square- 
yard  per  annum. 

170.  Method    of   Paying    for  Granite-block  Pavements. — The 
present  system  of  paying  for  granite-block  paving  is  erroneous. 
The  contractor  buys  his  blocks  at  so  much  a  thousand,  and  sells 
them  at  so  much  a  square  yard  laid ;  thus  it  is  his  interest  to  have 
as  few  blocks  to  the  square  yard  as  possible  and  joints  as  large  as  he 
can.     Or  he  may  purchase  them  from  the  stone  man  .at  so  much  a 
square  yard :  in  this  case  the  stone  man  is  interested  in  having  as 


STONE   PAVEMENTS.  H5 


few  blocks  as  possible;  as  is  also  the  contractor,  for  the  fewer 
blocks  to  be  laid  to  the  yard  the  more  yards  of  paving  will  the 
pavior  lay  in  a  day,  thus  increasing  the  profits  of  the  contractor. 
In  some  cases  the  pavior  is  paid  by  the  square  yard  of  paving;  then 
it  becomes  his  interest  to  have  as  few  blocks  to  handle  as  possible 
and  as  wide  joints  as  he  may,  thus  increasing  the  number  of  square 
yards  of  paving  he  can  lay  in  a  day,  and  thereby  increasing  his  wages. 
No  matter  how  looked  at,  all  parties  concerned  in  furnishing  and 
laying  the  blocks  are  deeply  interested  in  having  as  few  blocks  and 
as  wide  joints  as  possible  to  the  square  yard.  As  both  of  these  are 
serious  defects,  the  temptation  to  adopt  them  should  be  removed. 
The  number  of  blocks  to  be  laid  per  square  yard  should  be  clearly 
stated  in  the  specifications;  a  sum  should  also  be  designated  to  bo 
deducted  from  the  estimate,  by  way  of  a  penalty  or  forfeit,  for  every 
block  less  that  is  used  than  the  number  called  for.  As  the  labor 
expended  in  ascertaining  the  number  of  blocks  laid  to  each  square 
yard  would  be  very  great,  it  would  be  better  to  specify,  as  is  the 
custom  in  Liverpool,  that  four  courses  of  block  shall  not  measure 
more  than  fourteen  (14)  inches.  Under  this  rule  the  number  of 
blocks  laid  can  be  very  quickly  determined  by  measuring  any  four 
courses  at  random  over  the  length  of  the  street. 

City  Engineer  Horace  Andrews  of  Albany  has  introduced  with 
considerable  success  a  reform  in  the  manner  of  paying  for  granite 
block  pavements. 

The  following  unusual  clauses  are  taken  from  his  specifications, 
under  which  a  large  area  of  granite-block  pavement  has  been  laid : 

"It  is  expressly  understood  and  agreed,  by  and  between  the 
parties  hereto,  that  the  sum  paid  per  square  yard  for  granite  block 
pavement  shall  be  ascertained  and  fixed  as  follows — namely:  The 
number  of  granite  blocks  per  square  yard,  upon  which  the  bid  of 
the  proposer  is  based,  shall  be  24.  The  actual  average  number  of 
blocks  laid  per  square  yard  by  the  contractor  on  the  whole  street 
shall  be  determined  as  follows :  The  City  Engineer  shall,  from  time 
to  time,  during  the  progress  of  the  work,  measure  the  width  of  the 
blocks  as  laid  (by  measuring  the  aggregate  width  of  50  to  100 
courses,  from  this  deducing  the  average  width),  which  he  shall 
combine  with  the  average  length1  of  block  as  laid  (hereby  fixed  and 
determined  as  12£  inches),  for  the  purpose  of  computing  the 
number  of  blocks  laid  per  square  yard. 


116 


HIGHWAY   CONSTRUCTION. 


"  For  each  block,  or  fractional  part  thereof,  that  the  average 
number  laid  per  square  yard  shall  exceed  24  there  shall  be  added 
to  the  contractor's  bid  per  square  yard  an  amount  computed  at  the 
rate  of  9^  cents  per  block.  For  each  block,  or  fractional  part 
thereof,  that  the  average  number  laid  per  square  yard  shall  fall 
short  of  24,  there  shall  be  deducted  from  the  contractor's  bid  per 
square  yard  an  amount  computed  at  the  rate  of  9^  cents  per  block. 

"  In  order  to  lay  24  to  the  square  yard,  the  width  of  five  courses, 
including  the  joints  between  the  stones,  should  not  exceed  22 
inches." 

The  number  of  blocks  specified  per  square  yard  differed  on  the 
individual  streets;  otherwise  there  were  few  changes  in  the  above 
clauses. 

The  results  obtained  by  the  use  of  these  clauses  in  the  specifica- 
tions daring  the  last  two  years  are  indicated  in  the  following 

TABLE 

SHOWING  OPERATION  OF  SPECIFICATIONS  REGARDING  JOINTS  IN  GRANITE 
PAVEMENT  IN  1890  AND  1891. 


Width  9f 

Number  of 

Area  in 
Square 
Yards. 

Five  Courses 
as  laid. 
Inches. 

Blocks  laid 
per  Square 
Yard. 

Excess  or 
Deficiency. 

Contractor's 
Gain. 

Contractor's 
Loss. 

1 

3,624 

23.38 

22.62 

+  0.12 

$43.40 

2 

1,588 

23.13 

22.87 

+  0.37 

55.56 

3 

879 

23.50 

22.50 

0.00 

4 

11,202 

23.28 

22.72 

+  0.22 

238.61 

5 

3,918 

22.99 

23.01 

-1.99 

$740.09 

6 

15,218 

23.86 

22.17 

-0.33 

471.75 

7 

1.641 

24.57 

21.53 

-0.93 

150.93 

8 

2,363 

21.69 

24.39 

+  0.39 

87.44 

9 

2,146 

22.06 

23.98 

-  0.02 

4.29 

10 

2,679 

24.18 

21:88 

-0.62 

158.08 

11 

5,120 

24.91 

21.23 

-1.27 

614.38 

12 

2,846 

23.31 

22.70 

-  1.30 

350.01 

NOTE. — The  specified  number  of  blocks  per  square  yard  varied  on  different 
streets.     It  can  be  easily  found  from  columns  4  and  5. 

From  an  inspection  of  this  table  it  is  evident  that  close  paving 
can  be  secured.  Mr.  Andrews  believes  that  it  might  be  more 
beneficial  if  the  amount  of  deduction  for  non-fulfilment  were 
increased,  to  guard  against  the  contingency  of  wide  blocks  being 


STO^E    PAVEMENTS. 


IT 


obtainable  at  so  low  a  rate  as  to  make  it  profitable  for  a  contractor 
to  use  them  notwithstanding  the  deduction  from  his  contract  price 
per  square  yard. 

171.  Number  of  Granite  Blocks  per  Square  Yard.— Tible  XXVI 
shows  the   average  number  of  granite  blocks   of  different  sizes 


Width. 

Length. 

Average  Number  of 
Blocks  per  sq.  yd. 
Exclusive  of  Joints. 

Number  of  Square  Yards  1  ton 
will  cover  at  a  depth  of 

7  inches. 

9  inches. 

3  inches 

7  inches 

.        62 

2.50 

2.00 

3 

9 

48 

«< 

3 

10 

4° 

<: 

3 

12 

06 

< 

3i 

7 

53 

\ 

3* 

9 

41 

' 

3^ 

10 

37 

l 

8* 

12 

30 

i 

per  square  yard,  and  the  average  number  of  square  yards  that  one 
ton  of  granite  will  cover,  but  these  quantities  will  vary  with  the 
specific  gravity  of  the  stone  employed. 

172.  Cost  of  Construction. — The  cost  of  granite-block  pavements 
varies  greatly;  it  is  materially  affected  by  the  weight  of  the  blocks 
when  their  transportation  for  any  considerable  distance  has  to  be 
taken  into  account,  by  the  character  of  the  foundation  and  kind  of 
joint-filling,  and  frequently  by  the  condition  of  the  labor  market, 
demand,  etc. 

Tables  XXVII,  XXVIII,  XXIX,  and  XXX  show  the  extent 
and  cost  of  granite-block,  trap-block,  sandstone-block,  and  cobble- 
stone pavements  in  some  of  the  principal  cities  of  the  United  States 
in  1890. 


118 


HIGHWAY   CONSTRUCTION". 


TABLE  XXVII. 

EXTENT  AND  COST  OF  GRANITE-BLOCK  PAVEMENTS  IN  SEVERAL  OF  THE 
PRINCIPAL  CITIES  OF  THE  UNITED  STATES  IN  1890. 


Cities. 


Extent. 
Miles. 


Cost  of  Construction 
per  square  yard. 


New  York,  N.  Y 140.00 

Boston,  Mass 62.00 

Brooklyn,  N.  Y 55.30 

St.  Louis,  Mo 48.71 

Atlanta,  Ga , 33.,00 

Cincinnati,  Ohio 30.00 

Washington,  D.  C 23.20 

Chicago,  111 , 20.48 

Richmond,  Va 16.58 

Albany,  N.  Y 16.39 

Newark,  N.  J 13.36 

Lowell,  Mass 10.00 

Providence,  R.  I 9.20 

Troy,  N.  Y 9.12 

Milwaukee,  Wis 7.50 

Worcester,  Mass 7.00 

Omaha,  Neb 6.00 

New  Haven,  Conn 4.25 

Minneapolis,  Minn 4.16 

Cambridge,  Mass 3.63 

Trenton,  N.  J 3.50 

Los  Angeles,  Cal 1 . 50 

Wilmington,  N.  C 1.25 

Nashville,  Tenn 1 . 25 

Waterbury,  Conn 1.10 

St.  Paul,  Minn 0.39 

*Toronto,  Can 

*London  (City),  Eng 29. 00  ) 

(Vestries),  Eng 251. 00  f 

*Birmiugham,  Eng 26.00 

*Liverpool,          "    


$2. 50  to  $4. 50  f 
2.75  "     4.00J 
2.75 
3.52 
1.50 
4.25 
2.85  to 
3.13 
2.48 
2. 78  to 
2.75 
1.80  to 
2.50  " 


3.47f 


3.45f 

2.25 

4.00  f 

2.45 


2. 15  to 

2.25 

1.98 

2  50 

1.80  to 

2.20 

3.00 

2.52 

2.50 

3.15 

2. 75  to 

2.10 

3.00  to 

3.60  "    4.08 f 


3.75 


2.57 


2.95 
3.85f 


*  Foreign  cities  for  comparison. 

f  Concrete  foundation.     Where  not  noted  the  foundation  is  either  sand  or 
gravel. 


STONE    PAVEMENTS. 


119 


TABLE  XXVIII. 

EXTENT  AND  COST  OP  BELGIAN  BLOCK  (TRAP)  PAVEMENTS  IN  SOME  OF  THE 
PRINCIPAL  CITIES  OF  THE  UNITED  STATES  IN  1890. 


Cities. 

Extent. 
Miles. 

Cost  of  Construction 
per  square  yard. 

3STew  York  NY        

199  07 

<t>O     Kf\ 

Philadelphia  Pa  

119  60 

2  37 

•Brooklyn,  N.  Y  

22  41 

Patcrson   N  J           .  .  .  •  

2  75 

1  80  to  $2  14 

Camden  N  J     

2  08 

2  00 

Albany,  N.  Y  

1.42 

2.60 

Kingston.  N.  Y.  . 

1.90 

TABLE  XXIX. 

EXTENT  AND  COST  OF    SANDSTONE-BLOCK   PAVEMENTS  IN   SOME  OF   THE 
PRINCIPAL  CITIES  OF  THE  UNITED  STATES  IN  1890. 


Cities. 

Extent. 
Miles. 

Cost  of  Construction 
per  square  yard. 

Buffalo  N  Y     

138  00 

$2  00 

Toledo  Ohio  .         

17.48 

1.34 

Rochester  N  Y  

16.50 

2.25 

11  00 

1.98 

^Erie   Pa            

6.81 

2.78 

Elmira   N   Y  

5.00 

Utica  NY            

4  63 

Xiockport   N  Y  

4.00 

3  40 

1  80  to  $3.  69* 

2.98  "    3.94* 

*  Concrete  foundation. 


120 


HIGHWAY   CONSTRUCTION. 


TABLE  XXX. 
EXTENT  OP  COBBLESTONE  PAVEMENT  IN  THE  UNITED  STATES  IN  1900.* 


City. 

Square  Yards. 

City. 

Square  Yards. 

Baltimore  Md  

5  815  610 

Memphis  Tenn  ...*... 

56  073 

New  York,  N.  Y  

4  213,616 

Troy  N  *Y         

55  400 

Philadelphia  Pa  .  .  . 

2  920  664 

Springfield   Mass 

50  790 

1,213,000 

Columbus  O  

50,450 

Pittsburg  Pa  

1  147  415 

Chicago  111 

45  800 

New  Orleans,  La  

712  513 

Paterson   N  J  

42,240 

Louisville   K.y       • 

457  207 

Scrantou   Pa 

32  860 

San  F  nincisco   Cal  .... 

429  289 

Utica  N  Y 

29  682 

Albany  N  Y  

413  737 

Rochester  NY. 

27  780 

Allegheny  Pa  

397  690 

Detroit   Mich   

24,525 

Newark  N  J 

297  513 

Sacramento  Cul 

23  040 

Reading  Pa  

262  494 

Portland  Me     .  . 

22,355 

256,566 

Dubuqiic  la.  ....... 

19  941 

Washington,  D  C  

251,645 

Holyoke   Mass  

18,000 

New  Bedford,  Muss.  .  .  . 

210,140 

18,000 

Savannah  Ga  

178  291 

Peoria  111            

16  670 

Johnstown  Pa  

154  021 

Wilkesbarre  Pa 

15,178 

Sagiuaw  Mich       .   .  .  • 

108  541 

Grand  Rapids   Mich 

13  288 

Wheeling  W   Va     .. 

101  044 

Boston   Mass 

12  471 

Providence   R.  I.... 

89  408 

Fall  River   Mass  .... 

8  700 

Erie,  Pn  

86  371 

Bay  City   Mich     

6,444 

Norfolk,  Va  

85,000 

Elizabeth,  N.  J  

5,280 

Covington   Ky  

83  700 

Manchester  N   H.  .  .  . 

2  790 

Charleston,  S.  C  

82,530 

Trenton,  N   J  

2  579 

*  Cost  of  construction  ranges  from  $0.65  to  $1.50  per  square  yard. 

173.  Heads  of  Specifications  for  Granite-block  Pavement. 

(1)  Preparation  of  Roadbed. 

(2)  Foundation. 

(3)  Quality  of  the  Blocks. — The  paving-blocks   shall    be  of 
syenite  or  granite  from  or  other  approved  quarries.     All 
the  blocks  shall  be  of  the  same  quality  as  to  hardness,  color,  and 
grain ;  no  outcrop,  soft,  brittle,  or  laminated  stone  will  be  accepted. 
When  stone  is  obtained  from  more  than  one  quarry,  that  from  each 
quarry  shall  be  piled  and  laid  in  separate  sections  of  the  work.     In 
no  case  shall  the  stones  from  different  quarries  be  mixed. 

(4)  Dressing. — The  blocks  are  to  be  split  and  dressed  so  as  to 
present  regular  and  true  surfaces  on  all  sides,  with  straight  edges 
on  top,  bottom,  and  sides.    All  sides  of  the  block  must  be  free  from 
depressions  or  projections,  and  all  blocks  whose  faces  vary  more 
than  one  half  inch  from  rectangular  shape  will  be  rejected. 


STONE   PAVEMENTS. 


(5)  Size  of  the  Blocks.— The  blocks  shall  measure  3|  inches 
wide,  7  inches  deep,  and .  may  vary  between  9  and   12  inches  in 
length.     In  no  case  will  any  variation  in  the  width  be  permitted. 
In  some  cases,  as  paving  around  man-hole  heads,  etc.,  blocks  of 
lesser  depth  may  be  required,  and  will  be  used  as  directed  by  the 
engineer. 

(6)  Inspection  and  Culling.— -The  blocks  will  be  inspected  after 
they  are  brought  on  the  line  of  the  work,  and  all  blocks  which  in 
quality  and  dimensions  do  not  conform  strictly  to  these  specifica- 
tions will  be  rejected,  and  must  be  immediately  removed  from  the 
line  of  the  work.     The  contractor  must  furnish  such  laborers  as 
may  be  necessary  to  aid  the  inspector  in  the  examination  and  the 
culling  of  the  blocks ;  and  in  case  the  contractor  neglect  or  refuse 
to  furnish  said  laborers,  such  laborers  as  in  the  opinion  of  the 

may  be  necessary  will  be  employed  by  said  , 

and  the  expense  thus  incurred  by  will  be  deducted  and 

paid  out  of  any  money  then  due  or  which  may  thereafter  become 
due  to  said  contractor  under  the  contract  to  which  these  specifica- 
tions refer. 

(7)  Cushion-coat. — On  the  concrete  foundation  a  layer  of  clean 
sharp  sand  free  from  moisture  will  be  evenly  spread  to  a  depth  of 
one  half  inch.     The  sand  if  not  dry  must  be  made  so  by  the  appli- 
cation of  artificial  heat,  in  such  apparatus  as  may  be  suitable  for 
the  purpose  and  approved  of  by  the  engineer. 

(8)  Laying  the  Blocks. — The  blocks  will  be  bedded  in  the  sand, 
laid  stone  to  stone  in  parallel  courses  at  right  angles  to  the  axis  of 
the  street  (except  at  intersecting  streets,  where  they  will  be  laid  on 
the  diagonal  as  shown  on  the  plans).     Each  course  shall  consist  of 
blocks  of  uniform  width  and  depth.     The  blocks  shall  be  so  laid 
that  the  longitudinal  joints  shall  be  broken  by  a  lap  of  at  least  two 
inches. 

(9)  Jointing.— After  the  blocks  are  so  laid,  the  joints  between 
them  shall  be  filled  to  a  depth  of  two  inches  with  clean,  dry  gravel, 
then  rammed  to  an  unyielding  bearing  with  a  hand  rammer  weigh- 
ing not  less  than  fifty  pounds.     All  blocks  which  sink  below  the 
general  level  must  be  removed  and  replaced  with  blocks  of  greater 
depth.     After  the  blocks  are  rammed  the  paving  cement  will  be 
poured  into  the  joints,  to  a  depth  of  two  inches;  the  joints  will 
then  be  filled  flush  with  gravel  and  the  cement  poured  in  until  the 


122  HIGHWAY   CONSTRUCTION. 

joints  are  filled  and  will  absorb  no  more.  Dry  sand  will  then  be 
poured  along  the  joints  and  spread  over  the  entire  pavement.  The 
quantity  of  paving  cement  required  per  square  yard  of  pavement 
will  not  be  less  than  four  gallons.  This  quantity  must  'be  brought 
upon  the  ground,  and  whatever  may  remain  after  the  completion 
of  the  work  will  be  the  property  of  the  city.  Any  wastage  of  paving 
cement  by  pouring  over  the  surface  instead  of  between  the  blocks 
must  be  covered  with  a  sufficient  quantity  of  fine  dry  gravel  to 
absorb  it.  The  amount  so  wasted  will  be  estimated,  and  the  quan- 
tity so  estimated  must  be  replaced  by  the  contractor  at  his  expense. 

(10)  Composition  of  Paving  Cement. — The  paving  cement  will 
be  composed  of  the  residuum  obtained  from  the  direct  distillation  of 
coal-tar  and  creosote  oil,  in  the  proportion  of  fifty  gallons  of  oil  to 
one  ton  of  residuum;  the  two  ingredients  will  be  melted  together 
in  suitable  iron  boilers  having  a  capacity  of  not  less  than  one  ton. 
It  shall  be  poured  into  the  joints  while  in  a  boiling  state. 

(11)  Quality  of  the   Gravel. — The  gravel  used  for  filling  the 
joints  shall  be  free  from  sand,  clay,  or  other  objectionable  substances; 
it  shall  be  of  such  size  as  will  pass  entirely  through  a  sieve  of  three 
quarters  of  an  inch  mesh  and  be  retained  by  a  quarter-inch  mesh. 

(12)  Materials  to  be  Kept  Dry. — The  stone  for  the  pavement, 
the  sand  for  the  bed,  and  the  gravel  for  the  joints  shall  each  and 
severally  be  laid  only  when  dry  and  free  from  moisture.     After 
being  laid  the  contractor  shall  protect  them  from  the  weather  until 
the  joints  have  been  filled  with  the  paving  cement;  should  they 
become  moist  from  any  cause  previous  to  filling  the  joints  with  the 
said  cement,  the  contractor  shall  at  his  own  expense  remove  that 
portion  of  the  work  so  moistened  and  replace  and  complete  the 
same  with  dry  materials. 

(13)  Laying  Granite  Blocks  adjacent  to  Railway  Trades,  etc. 
Between,  and   one  foot  outside  of  railroad  tracks,  over  vaults, 
around  sewer-manhole  frames,  and  in  such   other  places  as  the 
engineer  may  designate,  the  contractor  shall  furnish  and  use  for 
the  pavement  blocks  of  such  lesser  depths  as  the  engineer  may 
direct.     The  general  dimensions  of  such  blocks  on  the  top  surface 
shall  be  the  same  as  for  the  main  pavement. 

(14)  The  number  of  blocks  laid  per  square  yard  shall  be  thirty, 
so  laid  that  ten  courses  measured  lengthwise  of  the  street  shall 
measure  not  more  than  35  inches.     The  actual  average  number  of 


STONE    PAVEMENTS.  123 


granite  blocks  laid  per  square  yard  shall  be  ascertained  by  the  city 
engineer;  and  for  each  block,  or  fractional  part  thereof,  that  the 
average  number  of  blocks  laid  per  square  yard  shall  fall  short  of 
thirty  there  shall  be  deducted  from  the  contractor's  bid  price  an 
amount  computed  at  cents  for  each  block  less  than  thirty. 

(15)  Interpretation  of  specifications. 

(16)  Omissions  in  specifications. 

(17)  Engineer  defined. 

(18)  Contractor  defined. 

(19)  Notice  to  contractors,  how  served. 

(20)  Preservation  of  engineer's  marks,  etc. 

(21)  Dismissal  of  incompetent  persons. 

(22)  Quality  of  materials. 

(23)  Samples. 

(24)  Inspectors. 

(25)  Defective  work,  responsibility  for. 

(26)  Measurements. 

(27)  Partial  payments. 

(28)  Commencement  of  work. 

(29)  Time  of  completion. 
^30)  Forfeiture  of  contract. 

{31)  Damages  for  non-completion. 

(32)  Evidence  of  the  payment  of  claims. 

(33)  Protection  of  persons  and  property. 

(34)  Bond  for  faithful  performance  of  work. 

(35)  Power  to  suspend  work. 

(36)  Eight  to  construct  sewers,  etc. 

(37)  Loss  and  damage. 

(38)  Old  materials,  disposal  of. 

(39)  Cleaning  up. 

(40)  Personal  attention  of  contractor. 

(41)  Payment  of  workmen. 

(42)  Prices. 

(43)  Security  retained  for  repairs. 

(44)  Payment,  when  made.     Final  acceptance. 


CHAPTER  IV. 
WOOD   PAVEMENTS. 

174.  Wood  Pavements.* — Pnvements  formed  of  wood  have  been 
extensively  employed  both  in  Europe  and  the  United  States,  bub 
with  widely  differing  results  in  the  two  countries.   The  experience  in 
the  United  States  has  been,  with  but  few  exceptions,  unsatisfactory, 
while  in  Europe,  especially  in  the  city  of  London,  wood  pavements 
have  proved  very  successful  and  are  quite  popular. 

175.  The  success  of  wood  pavements  in  Europe  is  due  to  the 
fact  that  more  care  is  exercised  in  their  construction  and  mainte- 
nance.    There,  a  solid  concrete  foundation,  well-seasoned  wood, 
and  water-proof  cement  filling  for  the  joints  are  employed,  with 
constant  and  careful  attention  to  keep  them  in  repair. 

176.  The  unsatisfactory  results  obtained  in  the  United  States 
are  attributable,  first,  to  the  methods  of  construction;  second,  to 
the  employment  of  green  wood;  and  third,  to  the  lack  of  careful 
maintenance. 

177.  The  advantages   of  wood  pavement  may  be  stated  as 
follows : 

(1)  It  affords  good  foothold  for  horses. 

(2)  It  offers  less  resistance  to  traction  than  stone  and  slightly 
more  than  asphalt. 

(3)  It  suits  all  classes  of  traffic. 

(4)  It  may  be  used  on  grades  up  to  five  per  cent. 

(5)  It  is  moderately  durable. 

(6)  It  yields  no  mud  when  laid  upon  an  impervious  foundation. 

(7)  It  yields  but  little  dust. 

(8)  It  is  moderate  in  first  cost. 

(9)  It  is  not  disagreeably  noisy. 

178.  The  principal  objections  to  wood  pavement  are: 

(1)  It  is  difficult  to  cleanse. 

(2)  Under  certain   conditions  of  the   atmosphere  it  becomes 
greasy  and  very  unsafe  for  horses. 

*  Wood  as  a  paving  material  appears  to  have  been  first  employed  in  Russia, 
where,  according  to  the  testimony  of  Barou  de  Bode,  it  has  been,  though 
rudely  fashioned,  used  for  some  hundreds  of  years. 

Wood  pavement  was  first  laid  in  New  York  during  the  year  1835-36,  and  in 
London,  Eng.,  in  1839. 

124 


WOOD   PAVEMENTS.  125 


(3)  It  is  not  easy  to  open  for  the  purpose  of  gaining  access  to 
underground  pipes,  and  rather  a  large  surface  has  to  be  removed  for 
this  purpose,  and  it  has  to  be  left  a  little  time  after  being  repaired 
before  traffic  is  again  allowed  upon  it. 

(4)  It  is  absorbent  of  moisture. 

(5)  It  is  claimed  by  many  that  wood  pavements  are  unhealthy. 
179.  Objections  to  Wooden  Pavements  on  Hygienic  Grounds. — 

Dr.  0.  W.  Wight,  Health  Officer  of  Detroit,  in  a  report  to  the  City 
Council,  says: 

"  On  sanitary  grounds,  therefore,  I  must  earnestly  protest  against 
the  use  of  wooden-block  pavements.  Such  blocks,  laid  endwise*, 
not  only  absorb  water  which  dissolves  out  the  albuminoid  matter 
that  acts  as  a  putrefactive  leaven,  but  also  absorbs  an  infusion  of 
horse-manure  and  a  great  quantity  of  horse-urine  dropped  in  the 
street.  The  lower  end  of  the  blocks,  resting  on  boards,  clay,  or 
sand,  soon  becomes  covered  with  an  abundant  fungoid  growth,  thor- 
oughly saturated  with  albuminous  extract  and  the  excreta  of  ani- 
mals in  a  liquid  putrescible  form.  These  wooden  pavements  undergo 
a  decomposition  in  the  warm  season,  and  add  to  the  unwholesome- 
ness  of  the  city.  The  street,  in  fact,  might  as  well  be  covered  a 
foot  deep  with  rotting  barnyard  manure,  so  far  as  unwholesomeness 
is  concerned.  Moreover,  the  interstices  between  the  blocks  and  the 
perforation  of  decay  allow  the  foul  liquids  of  the  surface  to  flow 
through,  supersaturating  the  earth  beneath,  and  constantly  adding 
to  the  putrefying  mass." 

M.  Fonssagrivs,  Professor  of  Hygiene  at  Montpellier,  France, 
objects  to  wooden  pavements  because  they  "consist  of  a  porous 
substance  capable  of  absorbing  organic  matter  and  by  its  own  de- 
composition giving  rise  to  noxious  miasma,  which,  proceeding  from 
so  large  a  surface,  cannot  be  regarded  as  insignificant.  I  am  con- 
vinced that  a  city  with  a  damp  climate,  paved  entirely  with  wood, 
would  become  a  city  of  marsh-fever." 

Professor  Brewer,  of  Yale  College,  says  that  "  even  in  the  free 
air  and  full  sunlight,  along  with  the  putrescence  a  white  fungous 
growth  begins  on  the  surface  of  the  wood,  which  rapidly  becomes 
slimy.  This  forms  much  more  rapidly  on  the  ends  of  the  grain  of 
the  wood  than  on  the  radial  or  tangential  sides.  The  fungous  growth 
goes  on,  modified,  of  course,  by  the  temperature  and  the  degree  of 
concentration,  and  it  continues  for  an  unknown  period,  or  until  the 


126  HIGHWAY    CONSTRUCTION. 

decay  has  become  complete.  Heartwood  and  sapwood  act  essen- 
tially alike  in  this  matter;  the  difference  is  one  of  degree  rather 
than  character." 

The  following  comments  are  from  the  report  of  a  Board 
appointed  by  the  Legislature  of  New  South  Wales  to  inquire  into  the 
alleged  deleterious  effects  of  wood  pavement  supon  the  public  health. 

"  The  Board  examined  specimens  of  wood  pavement  as  laid  in  the 
city  of  Sydney,  taking  up  blocks  at  different  points.  In  all  cases 
the  concrete  bed  underneath  was  moist;  in  three  cases  a  large 
amount  of  slimy  mud  was  found  giving  off  an  ammoniacal  odor. 
In  all  these  the  joints  and  blocks  appeared  to  be  uninjured.  The 
blocks  were  chemically  examined  to  determine  whether  they  had 
absorbed  organic  matter,  with  the  result  that  some  were  found 
impregnated  with  filth  to  the  very  centre,  while  others  were  com- 
paratively free  from  it. 

"  The  Board  comes  to  the  conclusion  that  wood  is  a  material 
which  cannot  safely  be  used  for  paving  unless  it  can  be  rendered 
absolutely  impermeable  to  moisture,  and  so  laid  that  while  the 
entrance  of  water  between  the  blocks  is  rendered  impossible,  the 
separation  of  the  fibres  at  the  surface  by  the  concussion  of  traffic  is 
also  effectually  prevented.  These  conditions  have  nowhere,  to  the 
knowledge  of  your  Board,  been  .fulfilled. 

"  So  far  as  the  careful  researches  of  your  Board  go,  the  porous, 
absorbent,  and  destructible  nature  of  wood  must,  in  its  opinion,  be 
declared  to  be  irremediable  by  any  process  at  present  known;  nor, 
were  any  such  process  discovered,  would  it  be  effectual  unless  it 
were  supplemented  by  another  which  should  prevent  fraying  of  the 
fibres.  Still  less  can  the  defects  of  wood  be  considered  to  be  of  less 
consequence  than  the  defects  of  other  kinds  of  material. 

"  In  this  city  it  may  perhaps  be  considered  that  an  amount  of 
wood  has  not  yet  been  laid  sufficient  to  affect  the  public  health 
whatever  its  condition  within  reasonable  limits  may  be;  and  upon 
this  ground  your  Board  does  not  recommend  that  the  present  pav- 
ing should  be  removed,  but  that  the  Board  of  Health  should  be 
empowered  to  examine  it,  and  to  report  upon  it,  from  time  to  time, 
with  a  view  of  ascertaining  its  behavior  under  longer  exposure  to 
weather  and  traffic  than  it  has  yet  had,  and  that  it  should  be  no 
longer  watered,  but  cleansed  by  sweeping  at  least  twice  a  day  (the 
sweeping  to  be  done  at  right  angles  to  the  direction  of  the  street,  or 


WOOD    PAVEMENTS. 


127 


parallel  to  the  courses,  so  that  the  latter  may  be  cleared  out  by  the 
broom),  in  order  that  destructive  dampness  and  penetration  of  dis- 
solved organic  matter  may  be  reduced  as  much  as  possible.  But  the 
presumption  is,  upon  the  evidence  here  adduced,  that  in  this  climate 
the  results  alluded  to  would  ensue  if  the  extent  of  surface  were 
sufficiently  enlarged  or  fouling  and  decay  sufficiently  extensive. 
Your  Board  therefore  recommends  that  the  paving  of  the  streets  of 
this  city  with  wood  should  be  discontinued,  and  desires  to  add  that 
this  recommendation  is  extended  to  apply  not  to  the  particular  mode 
of  construction  here  adopted  alone,  but  to  the  material  itself,  and  to 
every  known  method  of  construction." 

180.  Opinion  of  Col.  Hay  wood,  Engineer  of  the  City  of  London. — 
"  It  has  been  said  that  wood  pavements  at  times  smell  offensively 
and  may  be  unhealthy;  but  although  some  city  streets  have  been 
paved  with  wood  for  thirty  years,  no  complaints  that  I  am  aware 
of  have  been  made  to  the  commission  on  this  head,  and  the  in- 
habitants at  all  times  have  not  only  expressed  great  anxiety  lest  the 
wood  should  be  replaced  by  other  materials,  but  have  subscribed 
toward    the  cost    of  its  renewal.    ...   I  have  at  times   noticed 
offensive  emanations  from  it  near  cab-stands,  but  am  unable  to  find 
further  evidence  of  its  unhealthiness.     These  remarks  must  be  held 
to  apply  only  to  public  streets  open  to  the  sun,  air,  and  traffic;  in 
confined  places  and  under  some  conditions  wood  might  be  objec- 
tionable.     I   have   seen  it   decaying  in  confined  places  without 
traffic." 

181.  Wood  Pavements  and  Death-rate. — A  comparison  of  the 
death  rate  in  cities  using  wood  pavements  with  that  in  cities  where 
little  or  no  wood  is  employed  seems  to  show  that  wood  pavements 
do  not  cause  an  increase  in  the  death-rate. 


Death-rate 
per  1000. 

City. 

Percentage  of 
Wood  Pavements. 

17.48 

Chicago 

80 

25.19 

New  York 

0 

23.31 

Boston 

0 

19.74 

Philadelphia 

0 

14.70 

Detroit 

91 

16.90 

Milwaukee 

48 

23.70 

Nashville 

0 

19.87 

Atlanta 

0 

9.17 

Duluth 

95 

128 


HIGHWAY    CONSTRUCTION. 


FIG.  12.— SECTION  SHOWING  JOINT  FILLING, 


FIG.  13.  PLAN  OF  STREET  PAVED  WITH  WOOD  BLOCKS. 

SHOWING  ARRANGEMENT  OF  BLOCKS  AT  STREET  JUNCTIONS.    A  B  SHOWS 
THE  LINE  OF  TRAVEL  IN  TURNING  CORNERS. 


WOOD    PAVEMENTS.  129 


182.  Variety  of  Systems. — Since  the  introduction  of  wood  for 
paving,  upwards  of  forty  patented  systems  of  construction  have  been 
experimented  with.  The  difference  between  these  systems  consisted 
in  the  shape  of  the  blocks  and  the  treatment  of  the  wood  with 
chemicals.  The  shape  given  to  the  block  has  been  very  varied ; 
round,  square,  rectangular,  oblique,  hexagonal,  octagonal,  and  many 
complicated  forms  and  interlocking  devices  have  been  tried.  But 
experience  has  demonstrated  that  with  a  solid  foundation  there  is 
no  reason  for  complicated  shapes  or  interlocking  contrivances ;  and 
wood  pavements  in  their  modern  form  consist  of  either  rectangular 
or  cylindrical  blocks  set  with  the  fibre  of  the  wood  vertical,  with  the 
joints  between  the  blocks  as  narrow  as  possible  and  filled  with  a 
water-proof  cement. 

The  rectangular  blocks  are  prepared  by  cutting  with  circular 
saws  blocks  of  the  required  depth  from  planks  3  inches  thick  by  9 
or  12  inches  wide. 

The  cylindrical  blocks  are  prepared  by  sawing  from  round  logs 
pieces  of  the  required  length,  usually  6  inches.  These  6-inch  pieces 
are  passed  through  cylinders  furnished  with  steel  knives  that  remove 
the  bark  and  sap-wood,  and  leave  the  blocks  perfectly  round  and 
free  from  all  unevenness.  The  blocks  so  prepared  are  known  as 


FIG.  13A.  PAVEMENT  OF  ROUND  BLOCKS. 

"sapless"  cedar  blocks.  Figs.  12  and  13  show  the  manner  of  con- 
structing wood  pavements  as  practised  in  Europe.  Fig.  13^  shows 
a  typical  pavement  of  round  blocks  as  laid  in  the  United  States. 

183.  Number  of  Wood  Blocks  per  Square  Yard.— The  number  of 
rectangular  blocks  9  inches  long  by  3  inches  wide  required  per  square 
yard  is  44,  and  the  area  occupied  by  the  joints  will  be  equal  to  1 
square  inches. 


130  HIGHWAY    CONSTRUCTION. 

The  number  of  round  blocks  6  inches  in  diameter  required  per 
square  yard  is  30,  and  the  area  occupied  by  interspaces  will  be  278.28 
square  inches. 

184.  The  essentials  necessary  to  the  successful  construction  of 
wood  pavements  may  be  summed  up  as  follows: 

(1)  An  unyielding  and  impervious  foundation  (concrete). 

(2)  Sound  and  seasoned  wood,  either  in  its  natural   state  or 
treated  with  a  preserving  compound. 

(3)  An  impervious  filling  for  the  joints  between  the  blocks. 

185.  Foundations. — As  with  all  other  paving  materials  so  with 
wood,  without  an  unyielding  foundation  it  is  impossible  to  preserve 
a  smooth  surface.     The  foundations  most  commonly  employed  in 
the  United  States  are  wanting  in  solidity;  in  the  majority  of  cases 
the  blocks  are  set  in  sand  spread  on  the  natural  soil ;  in  others  they 
are  set  on  one  or  two  layers  of  plank  laid  on  sand.     The  advantage 
claimed  for  the  first  method  is  cheapness  ;  the  advantages  claimed 
for  the  second  method  are,  first,  that  the  flooring  of  planks  dis- 
tributes the  weight  or  pressure  applied  to  one  block  over  a  large 
surface,  and,  second,  that  the  boards  by  their  elastic  action  reduce 
the  wear  of  the  blocks.     This  latter  claim  is  fallacious  and  incon- 
sistent with  the  method  of  construction,  for  the  sand  bed  on  which 
the  planks  are  laid  is  supposed  to  solidly  support  them,  if  it  does 
so  the  planks  cannot  yield  elastically  under  pressure. 

186.  The  Chief  Cause  of  Failure  in  pavements  laid  on  a  foundation 
of  sand  and  planks  is  that,  as  soon  as  leakage,  even  to  the  slight- 
est extent,  commences  and  the  surface-water  finds  its  way  downward 
between  the  blocks,  there  is  nothing  to  prevent  its  reaching  and  sat- 
urating the  substratum  of  sand ;  since  the  boards,  although  close-laid, 
have  not  water-tight  joints,  the  water  will  pass  through  them  with 
comparative  freedom.  The  saturated  substratum  becomes  mobile 
and  subject  to  movement  under  variations  of  pressure.  Conse- 
quently when  a  load  passes  over  the  surface,  the  boards,  opposing 
an  inconsiderable  resistance  to  deflection,  are  pressed  downwards  by 
the  load,  and  they  recover  their  normal  position  when  the  load 
passes  away.  In  this  manner  a  pumping  action  is  set  up,  and  the 
sand  and  water,  mixed  with  other  loose  matter  at  the  bottom,  is 
pumped  up  to  the  surface  in  the  form  of  mud  and  slime.  Thus 
the  pavement  becomes  gradually  undermined,  and  the  undermining 
process  is  accelerated  by  the  form  of  the  pavement  itself,  which 


WOOD    PAVEMENTS. 


presents  a  continuous  diaphragm  under  which  the  exhausting  pro- 
cess is  extended  as  by  a  diaphragm-pump.  The  wetter  the  weather 
the  greater  is  the  action  of  undermining. 

In  addition  to  the  general  liability  of  leakage  through  the  pave- 
ment, there  is  a  special  difficulty  in  keeping  it  water-tight  at  the 
curb,,  where  it  is  comparatively  overhung  and  unsupported,  and 
where  there  is  at  the  same  time  a  constant  supply  of  water  for 
penetration  so  long  as  there  is  any  water  in  the  gutter. 

A  serious  consequence  of  the  flexibility  of  the  pavement  is  the 
numerous  breakages  of  the  blocks  by  splitting,  caused  by  the  un- 
equal strain  and  leverage  of  the  load  on  blocks  which  are  supported 
by  a  floor  partly  non-resisting  and  partly  resisting. 

187,  duality  of  Wood. — The  question  as  to  which  of  the  various 
kinds  of  wood  available  is  the  most  durable  and  economical  has  not 
been  satisfactorily  determined.    Many  varieties  have  been  tried.   In 
England  preference  is  given  to  Baltic  fir,  yellow  pine,  and  Swedish 
yellow  deal.     In  the  United  States  the  variety  most  used  (on  ac- 
count  of   its   abundance   and   cheapness)    is   cedar;    yellow  pine, 
tamarack,  and  mesquite  have  also  been  used  to  a  limited  extent. 
Cypress  and  juniper  are  being  largely  used  in  some  of  the  Southern 
States. 

Hard  woods,  such  as  oak,  etc.,  do  not  make  the  best  pavements; 
such  woods  become  slippery.  The  softer,  close-grained  woods,  such 
as  cedar,  cypress,  and  pine,  wear  better  and  give  good  foothold. 

The  wood  employed  should  be  sound  and  seasoned,  free  from 
sap,  shakes,  and  knots.  Deflective  blocks  laid  in  the  pavement 
will  quickly  cause  holes  in  the  surface,  and  the  adjoining  blocks 
will  suffer  under  wear  and  the  whole  surface  will  become  bumpy. 

188.  Chemical  Treatment  of  Wood. — The  great  enemy  of  all 
wood   pavements  is  decay,  induced  by  the  action  of  the  air  and 
water.     Wood  is  porous,  absorbs  moisture,  and  thus  hastens  its  own 
destruction.     Many  processes  have  been  invented  to  overcome  this 
defect,  such  as : 

(1)  Bttrnettizing.—Thia  process  consists  in  impregnating  the 
wood  with  a  solution  of  1  pound  of  chloride  of  zinc  to  4  gallons  of 
water.  Timber  treated  by  simple  immersion  requires  to  remain  in 
the  solution  for  about  two  days  for  each  inch  in  thickness,  and 
after  removal  requires  to  be  left  to  dry  for  about  14  to  20  days. 

The  process  is  more  expeditiously  performed  by  forcing  the 


132  HIGHWAY   CONSTRUCTION. 

solution  into  the  pores  of  the  wood  with  a  pressure  of  150  pounds 
to  the  square  inch. 

The  chief  advantage  of  this  process  is  that  it  renders  the  wood 
incombustible. 

(2)  Kyanizing. — In  this  process  the  timber  is  immersed  in  a 
saturated  solution  of  corrosive  sublimate  (bichloride  of  mercury)  in 
a  wooden  tank,  put  together  so  that  no  metal  of  any  kind  can  come 
in  contact  with  the  solution. 

One  pound  of  corrosive  sublimate  to  10  gallons  of  water  is  used 
when  a  maximum  strength  is  required,  and  1  pound  to  15  gallons 
of  water  when  a  minimum,  according  to  the  porosity  of  the  timber ; 
with  the  latter  proportion,  1J  pounds  will  be  sufficient  for  50  cubic 
feet  of  timber. 

The  time  required  to  saturate  the  timber  depends  on  its  thick- 
ness. Twenty-four  hours  are  usually  allowed  for  each  inch  in  thick- 
ness for  boards  and  small  timber;  large  timber  requires  from  a 
fortnight  to  three  weeks. 

(3)  Creosoting. — This    process    consists   in    impregnating  the 
wood  with  the  oil  of  tar  called  creosote,  from  which  the  ammonia 
has  been  expelled,  the  effect  being  to  coagulate  the  albumen  and 
thereby  prevent  its  decomposition,  also  to  fill  the  pores  of  the  wood 
with  a  bituminous  substance  that  excludes  both  air  and  moisture, 
and  which  is  noxious  to  the  lower  forms  of  animal  and  vegetable 
life.     In  adopting  this  process  all  moisture  should  be  dried  out  of 
the  pores  of  the  timber.     The  softer  woods,  while  warm  from  the 
drying-house,  may  be  immersed  at  once  in  an  open  tank  containing 
hot  creosote  oil,  when  they  will  absorb  about  8  or  9  pounds  per 
cubic  foot.     For  hard  woods,  and  woods  which  are  required  to 
absorb  more  than  8  or  9  pounds  of  creosote  per  cubic  foot,  the 
timber  should  be  placed  in  an  iron  cylinder  with  closed  ends,  and 
the  creosote,  which  should  be  heated  to  a  temperature  of  about 
120°  Fahr.,  forced  in  with  a  pressure  of  170  pounds  to  the  square 

-inch.  The  heat  must  be  kept  up  until  the  process  is  complete,  to 
prevent  the  creosote  from  crystallizing  in  the  pores  of  the  wood. 
By  this  means  the  softer  woods  will  easily  absorb  from  10  to  12 
pounds  of  the  oil  per  cubic  foot. 

The  most  effective  method,  however,  is  to  exhaust  the  air  from 
the  cylinder  after  the  timber  is  inserted,  then  to  allow  the  oil  to 
flow  in,  and  when  the  cylinder  is  full  to  use  a  force-pump  with  a 


WOOD    PAVEMENTS.  133 


pressure  of  150  to  200  pounds  per  square  inch,  until  the  wood  has 
absorbed  the  requisite  quantity  of  oil,  as  indicated  by  a  gauge 
which  should  be  fitted  to  the  reservoir-tank. 

The  oil  is  usually  heated  by  coils  of  pipe  placed  in  the  reservoir, 
through  which  a  current  of  steam  is  passed. 

The  quantity  of  creosote  oil  recommended  to  be  forced  into  the 
wood  is  from  8  to  12  pounds  per  cubic  foot. 

Into  oak  and  other  hard  woods  it  is  difficult  to  force,  even  with 
the  greatest  pressure,  more  than  2  or  3  pounds  of  that  oil. 

The  advantages  of  this  process  are,  the  chemical  constituents  of 
the  oil  preserve  the  fibres  of  the  wood  by  coagulating  the  alb  imen 
of  the  sap ;  the  fatty  matters  act  mechanically  by  filling  the  pores 
and  thus  exclude  water;  while  the  carbolic  acid  contained  in  the 
oil  is  a  powerful  disinfectant. 

The  life  of  the  wood  is  extended  by  any  of  the  above  processes 
by  preserving  it  from  decay,  but  such  processes  have  little  or  no 
effect  on  the  wear  of  the  blocks  under  traffic. 

The  process  of  dipping  the  blocks  in  coal-tar  or  creosote  oil  is 
injurious ;  besides  affording  a  cover  for  the  use  of  defective  or  sappy 
wood  it  hastens  decay,  especially  of  green  wood;  it  closes  up  the 
exterior  of  the  cells  of  the  wood  so  that  moisture  cannot  escape, 
thus  causing  fermentation  to  take  place  in  the  interior  of  the 
block,  which  quickly  destroys  the  strength  of  the  fibres  and  reduces 
them  to  punk. 

The  best  European  practice  of  to-day  favors  untreated  blocks. 

Considering  the  fact  that  in  the  United  States  large  quantities 
of  seasoned  timber  for  paving  cannot  be  obtained,  it  seems  advisable 
that  some  artificial  process  of  seasoning  be  employed.  The  most 
desirable  process  from  an  economic  and  sanitary  point  of  view  is 
the  process  of  impregnation  with  oil  of  creosote.  The  success 
of  this  process  depends  upon  the  elimination  of  all  moisture  from 
the  wood  before  the  oil  can  be  injected. 

The  woods  which  are  best  adapted  to  this  treatment  are  those 
which  are  most  absorbent  and  therefore  the  easiest  and  quickest 
destroyed,  as  the  gums  and  cottonwoods.  Cypress,  cedar,  pine,  and 
porous  oak  are  absorbent  and  can  be  successfully  treated. 

The  cost  of  creosoting  is  about  from  $12  to  $18  per  1000  feet, 
board  measure. 

189.  Dimensions  of  the  Blocks. — As  with  the  stone-block  pave- 


134  HIGHWAY   CONSTRUCTION". 

meuts  so  with  wood  blocks,  the  gauge  of  a  horse's  hoof  is  the  meas- 
ure of  the  maximum  width.  After  numerous  experiments  with 
widths  varying  from  3  inches  to  4|  inches,  European  engineers 
have  decided  upon  the  following  dimensions:  for  rectangular 
blocks,  width  3  inches,  depth  6  inches,  length  9  inches. 

The  advantage  of  the  narrower  width  is  that,  besides  affording  a 
more  ready  foothold  when  the  pavement  is  slippery,  narrow  blocks 
have  more  stability  than  wide  ones  of  the  same  depth. 

The  length  of  a  block  should  be  suitably  proportioned  to  the 
width;  a  length  of  12  inches  has  been  tried  and  found  to  be  too 
much  :  the  blocks  were  subject  to  splitting  across.  Nine  inches 
appears  to  be  the  most  suitable  length. 

For  round  blocks  the  diameter  should  not  exceed  6  inches;  the 
depth  may  be  the  same  as  for  the  rectangular  blocks,  6  inches. 
There  is  no  advantage  gained  by  a  greater  depth,  for  few  wood 
pavements  under  the  most  favorable  conditions  retain  a  sufficiently 
good  surface  after  about  six  years7  wear  without  extensive  repairs, 
and  it  is  therefore  not  advantageous  to  lay  blocks  of  a  greater 
depth  than  will  provide  for  a  duration  of  seven  years.  Six  inches 
is  sufficient  for  this. 

190.  Expansion  of  Blocks. — Wood  blocks  expand  on  exposure  to 
moisture,  and  when  laid  end  to  end  across  the  street  the  curbstones 
are  liable  to  be  displaced,  or  the  courses  of  blocks  will  be  bent  into 
reverse  curves.  To  avoid  this  the  joints  of  the  courses  near  the 
curb  may  be  left  open,  or  the  courses  next  the  curb  may  be  left 
out  until  expansion  has  ceased,  the  space  being  temporarily  filled 
with  sand.  The  rate  of  expansion  is  about  1  inch  in  8  feet,  but 
varies  for  different  woods.  The  time  required  for  the  wood  to 
become  fully  expanded  varies  from  12  to  18  months.  By  employ- 
ing blocks  impregnated  with  the  oil  of  creosote  this  trouble  will  be 
avoided.  Blocks  so  treated  do  not  contract  or  expand  to  any  appre- 
ciable extent. 

The  comparative  expansion  of  creosoted  and  plain  wood  blocks 
after  immersion  in  water  for  forty-eight  hours  in  percentage  on 
original  dimensions  was: 

Creosoted.  Plain. 

On  length  of  block 099  .6 

Onwidtli  "       "    57  .83 

Ondepth"       "    15  .31 


WOOD   PAVEMENTS.  135 


These  expansions  would  represent  in  a  carriageway  30  feet 
wide  2-J  inches  for  plain  blocks,  and  practically  f  inch  for  creosoted 
blocks. 

In  London  expansion  is  provided  for  by  leaving  a  space  of  1£ 
inches  between  the  blocks  and  the  curb.  This  space  is  filled  with 
clean,  dry  sand,  and  coated  over  with  a  film  of  Portland-cement 
mortar. 

191.  Width  of  Joints. — Experience  has  demonstrated  that  the 
wide  joints  once  thought  necessary  for  foothold  are  not  required. 
The  best  European  practice  of  to-day  is  to  make  the  joints  as  near 
one-quarter  of  an  inch  as  possible.    Wide  joints  hasten  the  destruc- 
tion of  the  wood  by  permitting  fibres  to  spread  under  the  traffic. 
"With  the  hard-wood  blocks  from  Australia  the  most  satisfactory 
results  are  secured  by  laying  them  as  closely  together  as  possible. 

192.  Filling   for   Joints.— The   best   materials   for   filling  the 
joints  are  bitumen  for  the  lower  two  or  three  inches,  and   hy- 
draulic cement-grout  for  the  remainder  of  the  depth.    The  cement- 
grout  protects  the  pitch  from  the  action  of  the  sun  and  does  not 
wear  down  very  much  below  the  surface  of  the  wood. 

193.  Durability. — The  life  of  wood  pavements  depends  upon 
the  quality  of  the  wood  used,  the  amount  and  weight  of  the  traffic, 
the  width  of  the  carriageway,  the  locality  (whether  open  or  con- 
fined), the  presence  of  street-railway  tracks,  and  the  frequency  of 
openings.     In  London  the  life  of  plain  or  untreated  blocks  has 
varied  from  five  to  twelve  years.     In  the  United  States  the  life  has 
varied  from  three  to  seven  years. 

The  life  of  creosoted  blocks  is  about  fifteen  years. 

Table  XXXI  (p.  136)  shows  the  actual  duration  and  cost  of 
certain  wood  pavements  in  the  city  of  London. 

"  The  average  life  of  the  pavements,  in  the  three  streets  with 
the  largest  traffic  was  about  9  years,  that  of  the  three  streets  with 
the  least  traffic  about  11J  years.  Nearly  all  before  they  were  re- 
moved had  been  relaid  over  -their  entire  surface,  and  some  new 
wood  introduced  from  time  to  time  in  lieu  of  that  found  too  de- 
fective to  relay." 

"  It  will  be  observed  that  the  wood  pavements  last  removed  had 
a  shorter  life  than  the  previous  pavements.  There  is  more  than 
one  reason  for  this,  but  it  should  be  stated  that  nearly  all  would  by 


136 


HIGHWAY   CONSTRUCTION". 


TABLE  XXXI. 

DURATION  AND  COST  OF  WOOD  PAVEMENTS  IN  THE  CITY  OF  LONDON.  * 
(Foundations  are  included,  but  no  excavation.) 


Situation. 

1 
1 

. 

2 
1 
| 

8-2 

i* 

fc 
1 

IP, 

Average  Cost  per  sq. 
yd.  per  annum. 

Cornhill  j 

May  1855 

yrs.     ms. 
10       2 

$2.92 

$4.17 

$0.70 

Gracechurch  St  •] 

July  1865 
Nov.  1853 

6       8 
11        7 

2.76 
3.04 

2.35 
4.11 

0.73 
0.61 

June  1865 
May  1851 

6       0 
9       4 

2.76 

2.28 

1.66 
1.44 

0.73 
0.39 

Lotbbury  Street  •! 

Sept.  1860 
May  1854 
Sept.  1860 
July  1841 

10       7 
12       3 
6       1 
19       1 

2.20 
3.00 
3.00 
3.44 

4.90 

6.87 
0.83 
3.20 

0.66 
0.80 
0.63 
0.35 

Bartholomew  Lane.  .  .  .  •! 

Aug.  1860 
May  1854 
Aug.  1866 

13       0 
12       3 
5       5 

2.20 
3.00 
3.00 

5.47 
4.19 
0.95 

0.59 
0.59 
0.73 

*  Report  of  Col.  Haywood. 

relay  and  the  introduction  of  some  new  wood  have  endured  a  few 
years  longer." 

194.  The  wood  pavements  of  Berlin  have  not  proved  as  durable 
as  those  of  London  and  Paris,  and  their  use  is  practically  aban- 
doned.    Those  of  Frankfort  (Ger.)  laid  under  the  Kerr  system  are 
giving  satisfaction,  and  are  said  to  be  in  as  good  condition  to-day 
as  when  laid  five  years  ago.     The  traffic  on  them  is  said  to  be  con- 
stant and  heavy. 

195.  W.  Weaver,  Chief  Engineer  and  Surveyor,  Kensington,. 
London,  says  wood  pavement  of  5-inch  creosote  blocks  will  last  ten 
years. 

196.  In  Chicago,  111.,  in  some  streets  wood  pavements  have 
lasted  upward  of  ten  years;  in  others  they  have  become  very  rough 
and  uneven  in  three  or  four  years,  while  in  the  river-tunnels  they 
have  worn  out  in  two  years. 

197.  The  wood  pavements  of  Washington,  D.  0.,  were  of  green 


WOOD    PAVEMENTS.  ]  37 


hemlock,  very  badly  constructed,  and  were  destroyed  by  decay  and 
dry-rofc  in  about  four  years. 

198.  In  St.  Louis,  Mo.,  the  average  life  of  the  Nicholson  pave- 
ments was  six  years. 

199.  In  Detroit,  Mich.,  the  Board  of  Public  Works  consider 
that  cedar-block  pavements  will  last  eight  years  before  extensive 
repairs  are  necessary,  but  that  it  is  better  to  make  repairs  earlier. 

200.  Mr.  R.  AV.  Roberts,  City  Surveyor  of  East  Saginaw,  Mich., 
in  his  report  for  1889  says:  "Eight  to  ten  years  is  the  estimated 
life  of  cedar-block  pavement  laid  on  sand  and  board  foundation/' 

201.  Duluth,  Minn. — Experience  shows  that  on  grades  between 
4  and  13  per  cent  the  best  surface  is  formed  of  blocks  not  more 
than  6  inches  in  diameter,  laid  on  concrete  foundation,  and  joints 
filled  with  Portland-cement  grout. 

Tar  composition  is  found  to  hasten  rather  than  retard  decay. 

On  light  grades  and  clay  subsoil  a  broken-stone  or  "  telford " 
foundation  is  considered  to  have  an  advantage  over  concrete  for  the 
reason  that  every  portion  of  the  subgrade  is  thoroughly  compacted 
by  the  roller,  the  broken  stone  being  forced  down  into  the  numer- 
ous soft  spots.  Openings  for  repairs  to  underground  structures 
cannot  be  as  completely  restored  to  their  original  condition  as  can 
concrete,  it  being  impracticable  to  thoroughly  consolidate  the 
broken  stone  without  the  use  of  a  heavy  roller. 

The  broken-stone  or  telford  foundation  consists  of  two  layers 
of  stone;  the  first  6  inches  thick,  composed  of  large  stones  thor- 
oughly wedged  together,  all  chinks  filled  with  smaller  stones,  and 
the  whole  surface  covered  with  a  layer  of  wet  gravel  and  compacted 
with  a  20-ton  steam-roller.  The  second  layer  is  2  inches  thick,  com- 
posed of  broken  stone  not  more  than  2  inches  in  the  greatest  dimen- 
sion. It  is  spread,  covered  with  wet  gravel,  and  rolled  like  the  first 
course.  On  top  of  this  is  sprinkled  a  thin  layer  of  sand,  which  is 
covered  by  a  course  of  1-inch  plank,  making  a  smooth  and  uniform 
surface  on  which  to  lay  the  blocks. 

202.  Wear. — The  wear  of  wood  pavements  is  generally  consid- 
ered to  be  as  much  due  to  the  action  of  the  horses'  feet  as  to  that 
of  the  wheels,  and  the  action  of  the  former  is  more  destructive  on 
steep  grades;  the  wear  is  also  increased  by  wide  joints. 


138 


HIGHWAY    CONSTRUCTION". 


The  wear  of  wood  pavements  by  the  abrading  action  of  traffic  is 
stated  by  various  authorities  as  follows : 

TABLE  XXXII. 
WEAR  OF  WOOD  PAVEMENTS. 


Wear  per  annum  under  a  traffic  tonnage, 
per  yard  of  width. 

Locality  and  Authority. 

1200  vehicles,  per  12  hours  
1106  tons    

.81  inch 

*    " 
.456    '• 
.065    " 

i    " 

.58    " 

j  King  William  Street,  London. 
(  Col.  Haywood. 
j  Parliament  Street,  London. 
(  G.  H.  Stay  ton,  Engineer. 
(  Fleet  Street,  London. 
}  G.  H.  Staytou,  Engineer. 
j  Sloane  Street,  London. 
(  G.  H.  Stayton,  Engineer. 
j  Great  Howard  Street,  Liverpool. 
(  G.  Dunscombe,  Engineer. 

1360     "     

279      «    

94  000"     

302  000  tons  

The  wear  in  the  latter  years  of  the  life  of  the  wood  was  found 
to  be  greater  than  in  the  first  years.  The  wear  between  street-car 
rails  is  about  one  third  more  than  the  remainder  of  the  roadway. 

Experiments  made  to  ascertain  in  which  position  the  fibre  of 
wood  offered  the  greatest  resistance  to  the  wear  of  traffic  gave  the 
following  results : 

Vertical  fibre wore  .125  of  an  inch 


At  angle  of  75  degrees 
"       "      "  60        " 
"      "      "  45 

"      "      "  30       "       . 
«      «      «  15        «       § 

Horizontal..  ... 


.147 
.182 
.250 
.310 
.375 
.500 


203.  St.  Paul,  Minn. — The  cedar-block  pavement  laid  in  1882, 
on  a  plank  and  sand  foundation,  shows  after  seven  years'  use  a  wear 
of  2  to  2-j-  inches   under  ordinary  traffic  ;    on   recent   investiga- 
tion the  blocks  showed  very  little  decay,  but  the  one-inch  founda- 
tion-plank showed  considerable.     Two-inch  planks  are  now  used. 

204.  St.  Louis,  Mo.— On  Third  Street,  with  a  traffic  of  2400 
vehicles  in  24  hours,  6-inch  blocks  of  prepared  cotton  wood  wore 
down  1£  inches  in  seven  years. 


WOOD    PAVEMENTS. 


139 


205.  The  cost  of  construction  of  wood  pavements  ranges  be- 
tween $1.00  and  $4.00,  depending  upon  the  quality  of  the  wood 
and  whether  it  be  plain  or  creosoted,  and  upon  the  character  of  the 
foundation. 

Table  XXXIII  shows  the  cost  in  various  localities  in  the  United 
States. 

TABLE  XXXIII. 

EXTENT  AND  COST  OF  WOOD  PAVEMENTS  IN  VARIOUS  LOCALITIES  IN  THE 

UNITED  STATES. 


Cities. 


Extent. 
Miles. 


Cost  of  Construction 
per  square  yard. 


Chicago,  111 410 . 00 

Detroit,  Mich 116.19 

St.  Paul,  Minn 35.97 

Milwaukee,  Wis 30 . 00 

Minneapolis,  Minn 25 . 85 

Omaha,  Neb 25.00 

Springfield,  111 20.00 

Grand  Rapids,  Mich 14.63 

Toledo,  Ohio 12.09 

Washington,  D.  C 0.60 

St.  Louis,  Mo 0.19 

Elmira,  N.  Y 

St.  Joseph,  Mo 

East  Saginaw,  Mich 16.59 

*Toronto,  Can 109.57 

*Londou,  Eng.  (City) 6.00 

"      (Vestries) 47.00 

*Birmingham,  Eng ...  6.00 

*Paris,  France 


$1.16 

1.82 

$1.20  to  $1.40 
1.05  "  1.25 
0.95  " 


2.65 
1.40f 

$3. 00  to  $4. 30 

2.52 
4.60** 


*  Foreign  cities  for  comparison. 

t  Treated  blocks.  \  Plank  foundation.  §  Gravel  foundation. 

||  Cedar  on  concrete.  If  Tamarack  on  concrete. 

**  Includes  about  30  cents  for  the  municipal  tax  on  the  material  used. 

206.  Cost  of  Maintenance. — With  regard  to  the  cost  of  mainte- 
nance in  the  United  States  but  little  information  can  be  obtained. 
St.  Louis,  Mo.,  reports  the  cost  of  maintaining  pine-block  pavement 
as  5  cents  per  square  yard  per  annum,  burnettized  cottonwood  at 
4|  to  6  cents.  London,  England,  reports  the  cost  of  maintenance  at 


140 


HIGHWAY,  CONSTRUCTION. 


from  16  to  36  cents  per  square  yard  pea-  annum,  or  including  all 
renewals  44  cents  per  annum.  In  Paris  the  cost  ranges  from  46  to 
54  cents. 

The  practice  of  the  companies  engaged  in  the  construction  of 
wood  pavements  in  Europe  is  to  guarantee  to  keep  the  pavement  in 
repair  free  of  charge  for  one  or  two  years,  and  then  for  so  many 
years  after  at  so  much  per  annum.  About  $3.36  per  square  yard  is 
generally  the  first  cost  of  construction,  and  24  cents  the  annual 
charge  for  maintenance. 

Table  XXXIV  shows  the  annual  cost  of  maintaining  certain 
wood  pavements  in  London. 


TABLE  XXXIV. 

FIRST  COST  AND  TENDERED  COST  PER  ANNUM  FOR  MAINTAINING  CERTAIN 
WOOD  CARRIAGEWAY  PAVEMENTS  IN  THE  CITY  OP  LONDON. 


1 

{ 

^§ 

>er  square 

IP 

«_l  W  » 

lit 

i1 

Situation. 

I 

0 

O-^u 

Ml 

1  . 

ijsl 

OS® 

ft! 

* 

fi 

2.11 

11 

ti-pis 
B  S  S 

T3  ft 

73  "  — 

"a 

2 

! 

ill 

|g| 

g<a 

Q 

e 

>H 

!* 

^^ 

3 

King  William  St. 

Feb.  1873 

(  Improved  ) 
1    Wood.     [ 
(  Pav.Co.  j 

16 

84.88 

j  1  yr.  free,  15  yrs.  ) 
1    at36cts.=$5.40  j 

$9.72 

$0.61 

Ludgate  Hill. 

Nov.  1873 

Ditto 

16 

4.32 

1  1  yr.  free,  15  yrs.  ! 
J    at  36  cts.=$5.40  f 

9.72 

0.61 

Portions  of  Great  ) 
Tower  St.  and  > 
Seething  Lane.  ) 

Sept.  1873 

Ditto 

16 

3.84 

j  1  yr.  free,  15  yrs.  ) 
1    at30cts.=$4.50f 

8.34 

0.52 

207.  Assuming  the  life  to  be  7  years,  Mr.  Stay  ton  estimates 
the  annual  cost  of  wood  paving  in  Chelsea,  England,  with  a  traffic 
of  500  to  750  tons  per  square  yard  of  width  per  day,  to  be  42  cents 
per  square  yard,  which  includes  the  cost  of  original  construction, 
repairing,  renewals,  and  interest  spread  over  15  years.     Cleansing 
and  sanding  are  estimated  to  cost  10  cents  per  square  yard  in  ad- 
dition. 

208.  Description  of  Various  Systems  of  Wood  Paving. — Cedar- 
block  Pavement,  Detroit,  Mich. — The  cedar-block  pavements  used 
here  are  made  of   sound  blocks,  stripped  of  bark,  cylindrical  in 


WOOD    PAVEMENTS. 


shape  and  not  more  than  9  inches  nor  less  than  5  inches  in  diame- 
ter and  7  inches  deep.  These  blocks  rest  on  a  bed  of  bank  sand 
and  gravel  6  inches  deep,  well  compacted  with  a  roller  weighing 
2400  pounds.  After  •  the  blocks  are  set  they  are  rammed  to  a  solid 
bearing  with  a  rammer  weighing  80  pounds;  the  spaces  between 
them  are  filled  with  screened  gravel  rammed  in  with  steel  bars. 
The  surface  of  the  finished  pavement  is  finally  covered  with  gravel 
and  sand  to  a  depth  of  f  of  an  inch. 

209.  Mesquite-block   Paving  in  San  Antonio,  Tex. — The  blocks 
are  hexagonal  in  shape,  the  minimum  diameter  being  4  inches  and 
the  maximum  8  inches,  with  a  depth  of  5  inches.     The  blocks  are 
sawed  with  a  slight  batter,  making  the  top  about  J  of  an  inch 
smaller  than  the  bottom. 

The  roadbed  is  excavated  to  the  required  depth  and  rolled 
with  a  steam-roller. 

The  foundation  is  6  inches  of  cement  concrete.  A  cushion- 
coat  of  sand  1  inch  in  depth  is  spread  over  the  concrete  and  the 
blocks  bedded  thereon.  The  joints  are  sand-filled,  The  cost  per 
square  yard,  including  foundation,  is  about  $2.80. 

210.  Asphalt  Wood  Pavement.  — This  is  one  of  the  more  recently 
adopted  pavements  in  England.     It  consists  of  a  concrete  founda- 
tion, on  which  is  placed  a  coating  of  asphalt  mastic  one-half  inch 
thick ;  the  blocks  are  creosoted  and  are  placed  on  the  asphalt  with 
spaces  of  half  an  inch  between  rows,  and  the  joints  are  broken  by  a 
lap  of  at  least  two  inches.     The  lower  portion  of  the  spaces  for  2  to 
2  j-  inches  up  is  filled  with  melted  asphalt  and  the  remainder  with 
cement-grout  and  gravel.     In  London  this  costs  $4.00  per  square 
yard. 

211.  Henson  Pavement. — The  Henson  system,  which  has  been 
largely  used  in  London,  is  as  follows :  The  blocks  are  bedded  and 
jointed  with  ordinary  roofing-felt,  a  strip  of  which,  cut  to  a  width 
equal  to  the  depth  of  the  blocks,  is  placed  between  every  two  courses. 
The  joint  is  made  as  close  as  possible  by  driving  up  the  blocks,  as 
every  eight  or  ten  courses  are  laid,  with  heavy  mallets,  a  plank  being- 
laid  along  the  face  of  the  work;  a  perfectly  close  and  slightly  elastic 
joint  is  thus  formed.     A  continuous  layer  of  felt  is  likewise  laid 
over  the  concrete  foundation  to  give  a  slightly  elastic  bed  to  the 
blocks.     The  surface  of  the  pavement  is  dressed  over  with  a  hot 
bituminous  compound,   and  covered  with  fine  clean   grit.      The 


142  HIGHWAY    CONSTRUCTION. 

blocks  are  laid  in  courses  at  right  angles  to  the  curb,  any  change  in 
the  latter  being  accommodated  by  shorter  courses  ending  with 
wedge-shaped  blocks.  At  street-intersections  the  courses  are  laid 
diagonally  or  meeting  at  right  angles.  Two  or  three  courses  are 
laid  parallel  with  the  curb  to  form  the  gutter. 

212.  Improved  Wood-pavement  Company. — The  method  em- 
ployed by  this  company  in  constructing  the  wood  pavements  in 
Paris  is  as  follows  : 

(1)  Foundation. — This  consists  of  a  bed  of  Portland-cement 
beton  0.15  m.  (6  inches)  thick,  with  a  top  coat  of  cement  mortar 
about  0.01  m.  (f  inch)  thick.  The  beton  is  thus  proportioned :  A 
mixture  of  about  one  third  sand  and  two  thirds  gravel  is  put  in  a 
bottomless  box  containing  half  a  cubic  meter  (0.65  cubic  yard),  and 
after  the  removal  of  the  box  100  kilograms  (220  pounds)  of  cement 
are  emptied  on  the  heap.  This  is  in  the  proportion,  by  volume,  of 
about  one  seventh  as  much  cement  as  there  is  sand  and  gravel,  since 
1400  kilos  is  the  mean  weight  of  a  cubic  meter  of  good  Portland 
cement  heaped  loosely. 

The  sand  was  dredged  from  the  bed  of  the  Seine,  and  the  gravel 
taken  from  pits  on  the  seashore.  The  cement  was  furnished  by 
the  manufactory  of  Demarle  &  Lonquety,  of  Boulogne-sur-Mer. 

The  paving-blocks  have  a  uniform  thickness  and  are  not  laid 
on  the  bed  of  beton  until  after  it  has  set,  in  order  to  exactly 
preserve  the  curvature  of  the  surface  of  the  beton  required  for  the 
convexity  of  the  roadway.  In  the  Avenue  des  Champs  Elysees  the 
convexity  was  0.42  m.  (16|  inches)  in  a  width  of  27  m.  (87  feet  7 
inches),  which  represents  a  mean  transverse  slope  of  a  little  more 
than  3  in  100.  This  convexity,  though  less  than  first  proposed  by 
the  company,  appears  to  be  a  little  excessive,  and  it  seems  that  for 
roads  under  satisfactory  drainage  conditions  the  convexity  might  be 
diminished:  0.42m.  is  only  a  mean  convexity,  for,  on  account  of 
the  small  longitudinal  slope  of  the  avenue,  the  grade  of  the  gutters 
is  not  parallel  to  the  grade  of  the  street,  but  presents  a  series  of 
short  slopes  from  the  hydrants  to  the  sewer-openings ;  consequently 
the  convexity  varies  from  0.39  m.  (15J  inches)  at  the  hydrants  to 
0.45  m.  (17|  inches)  at  the  sewers. 

To  exactly  regulate  the  surface  of  the  beton  a  series  of  trans- 
verse profiles  were  defined  by  stakes  levelled  to  the  grade  of  the  top 
of  the  bed.  Along  each  profile  a  strip  of  stiff  beton  was  laid.  The 


WOOD    PAVEMENTS.  143 


top  of  this  beton  was  carefully  levelled  and  smoothed  and  received 
a  guide-rule,  laid  flat,  whose  thickness  exactly  corresponded  with 
that  of  the  beton  coating.  This  series  of  rules  thus  formed  a  set 
of  guides  close  together,  between  which  it  was  easy  with  large 
straight-edges  to  level  the  beton  to  the  required  surface.  The  first 
levelling  could  never  be  more  than  approximate,  the  surface  of  the 
beton  naturally  remaining  somewhat  rough.  The  exact  level  re- 
quired, as  fixed  by  the  tops  of  the  rules,  was  secured  by  the  top 
coat  of  cement  mortar  which  filled  the  spaces  between  the  pebbles 
and  made  an  exact  surface.  This  mortar  was  first  composed  of  200 
kilos  of  cement  to  a  cubic  meter  of  sand  (336  pounds  to  the  cubic 
yard),  but  this  proportion  proving  too  small  it  was  increased  to  300 
kilos.  It  was  always  mixed  with  a  great  excess  of  water,  so  as  tov 
penetrate  the  interstices  of  the  gravel. 

(2)  Paving. — The  covering  is  formed  of  small  uniform  blocks 
of  red  Northern  fir,  0.15  m.  (6  inches)  high,  0.22  m.  (8f  inches) 
long,  and  0.08  m.  (3£  inches)  wide.  These  are  set  close  lengthwise, 
with  joints,  transverse  to  the  street,  of  about  1  centimeter  (f  inch). 
The  blocks  are  sent,  ready  for  use,  from  England,  where  they  were 
cut  from  planks  of  the  ordinary  size,  0.08  m.  thick  by  0.22  m.  wide. 
The  third  dimension,  taken  in  the  length  of  the  plank,  forms  the 
height  of  the  block,  so  that  in  position  the  fibres  of  the  wood  are 
placed  upright.  The  blocks  are  superficially  creosoted  after  being 
cut. 

When  the  foundation  has  set,  two  or  three  days  after  being  laid, 
the  blocks  are  set  by  the  pavers.  Owing  to  the  light  weight  of  the 
blocks  the  work  of  paving  is  very  rapid.  Between  crossings  the 
blocks  are  set  in  rows  perpendicular  to  the  axis  of  the  street,  with 
their  longitudinal  joints  staggered  exactly  half  the  length  of  a 
block.  The  methods  used  at  crossings  to  avoid  a  continuous  joint 
parallel  to  the  traffic  are  analogous  to  those  used  in  stone-paving. 
Special  precautions  are  taken  to  insure  exact  spacing  and  regu- 
larity of  the  rows.  Before  commencing  a  new  row,  a  strip  of  wood 
whose  thickness  is  exactly  that  of  the  required  joint  is  set  edgewise 
in  contact  with  the  last  row,  and  the  paver  has  only  to  set  the  ad- 
jacent blocks  in  contact  with  it. 

The  blocks  do  not  at  first  adhere  to  the  foundation  and  are 
easily  displaced  after  the  removal  of  the  strips;  to  maintain 
them  in  place,  as  soon  as  the  strips  are  taken  out  a  small  quantity 


144  HIGHWAY   CONSTRUCTION". 

of  bitumen  is  poured  into  the  joints.  This  liquid  material  fills  the 
small  spaces  that  may  exist  under  the  blocks  and  partially  fills  the 
joints,  and  in  solidifying  effectually  seals  the  blocks. 

The  joints  are  then  filled  by  a  thin  grouting  of  neat  Portland 
cement,  distributed  by  the  aid  of  a  broom.  This  is  done  at  least 
twice  to  insure  perfect  filling  and  the  essential  impermeability. 

The  pavement  cannot  be  opened  for  traffic  until  after  the  ce- 
ment in  the  joints  has  completely  set,  for  which  a  delay  of  four  or 
five  days  is  considered  necessary.  During  this  interval  the  last 
operation  is  performed,  viz.,  spreading  a  thin  layer  of  dry  sharp 
sand  over  the  surface.  The  company  claims  that  this  dressing, 
crushed  under  the  action  of  the  wheels,  incrusts  itself  in  the  wood 
and  lends  resistance  to  the  wearing  surface.  It  seems  more  prob- 
able that  this  coating  is  simply  to  protect  the  fresh  mortar  from 
the  direct  action  of  the  wheels,  for  it  can  be  maintained  but  a  very 
short  time  on  a  travelled  road,  and  is  soon  transformed  into  a  dis- 
agreeable greasy  mud. 

213.  Heads  of  Specifications  for  Wood-block  Pavement. 

(1)  Preparation  of  Roadbed. 

(2)  Foundation. 

(3)  Cushion-coat. — The  cushion-coat  shall  consist  of  a  layer  of 
dry,  clean,  sharp  sand  evenly  spread  on  the  concrete  to  a  depth  of 
one-half  inch. 

NOTE. — Asphaltlic  paving-cement  may  also  be  used  for  the 
cushion-coat;  or  the  blocks  may  be  laid  directly  upon  the  concrete. 

(4)  Quality  of  the  Blocks. — The  blocks  shall  be  of 
timber,  sound  and  thoroughly  well  seasoned,  free  from  all   sap, 
shakes,  large  and  loose  knots  or  other  defects. 

NOTE. — If  the  blocks  are  to  be  creosoted,  the  number  of  pounds 
of  creosote  that  should  be  absorbed  in  a  cubic  foot  of  the  wood 
should  be  specified;  this  is  generally  about  10  Ibs.  of  creosote  to  1 
cubic  foot  of  wood. 

(5)  Size  of  the  Blocks. — (Rectangular:)  The  blocks  must  not  be 
less  than  6  inches  nor  more  than  12  inches  in  length  by  3  inches  in 
width  and  6  inches  in  depth.     (Round  Blocks :)  The  blocks  shall 
not  be  less  than  4  inches  nor  more  than  8  inches  in  diameter, 
with  a  uniform  length  of  6  inches.     Each  block  to  be  of  uniform 
cross-section   from   end  to  end,  the   ends  to  be  sawn  off  at  right 
angles  to  the  axis.    The  diameter  of  the  block  preferred  is  4  inches, 


WOOD    PAVEMENTS.  145 


and  70  per  cent  of  the  whole  number  of  blocks  furnished  must  be 
of  this  size. 

(6)  Inspection  and  Culling. — The  blocks  will  be  inspected  aftei 
they  are  brought  on  the  line  of  the  work,  and  all  blocks  which  in 
quality  and  dimensions  do  not  conform  strictly  to  these  specifica- 
tions will  be  rejected  and  must  be  immediately  removed  from  the 
line  of  the  work.     The  contractor  must  furnish  such  laborers  as 
may  be  necessary  to  aid  the  inspector  in  the  examination  and  culling 
of  the  blocks  ;  and  in  case  the  contractor  neglect  or  refuse  to  fur- 
nish said  laborers,  such  laborers  as  in  the  opinion  of  the 

may  be  necessary  will  be  employed  by  said  ,  and  the 

expense  thus  incurred  by  will  be  deducted  and  paid 

out  of  any  money  then  due  or  which  may  thereafter  become  due  to 
said  contractor  under  the  contract  to  which  these  specifications 
refer. 

(7)  Cushion-coat. — On  the  concrete  foundation  a  layer  of  clean 
sharp  sand,  free  from  moisture,  will  be  evenly  spread  to  a  depth  of 
one-half  inch.   The  sand,  if  not  dry,  must  be  made  so  by  the  appli- 
cation of  artificial  heat  in  such  apparatus  as  may  be  suitable  for 
the  purpose  and  approved  of  by  the  engineer. 

(8)  Laying  the  Blocks. — The  blocks  (rectangular)  shall  be  set 
on  the  cushion-coat  with  the  fibre  vertical,  in  parallel  courses,  with 
the  length  of  the  blocks  at  right  angles  to  the  axis  of  the  street; 
any  change  in  the  direction  of  the  latter  being  accommodated  by 
shorter  courses  ending  in  wedge-shaped  blocks.      No  joints  shall 
exceed  f  of  an  inch  in  width.     The  blocks  shall  be  so  laid  that  all 
longitudinal  joints  will  be  broken  by  a  lap  of  at  least  2  inches.     At 
street-intersections  the  courses  are  to  be  laid  diagonally  as  shown 
in  Fig.  13. 

The  gutters  will  be  formed  by  three  courses  of  blocks  laid  par- 
allel to  the  curb;  the  course  adjoining  the  curb  will  be  left  out 
until  expansion  has  ceased.  The  space  so  left  unpaved  will  be  filled 
with  sand. 

(9)  Laying  the  Blocks  (round  blocks).— The  blocks  will  be  laid 
on  the  cushion-coat,  in  parallel  rows  across  the  street  and  in  close 
contact  with  each  other.     Split  blocks  shall  be  used  adjoining  the 
curbs,  around  sewer-manhole  heads,  and  at  such  other  places  as  the 
engineer  may  direct   but  no  split  blocks  shall  be  laid  in  the  main 
pavement. 


146"  HIGHWAY   CONSTRUCTION. 

(10)  Ramming. — After  the  blocks  are  so  laid   they  shall  be 
rammed  to  a  solid  bearing  with  a  hand  rammer  weighing  not  less 
than  50  pounds.     All  blocks  which  sink  below  the  general  level 
shall  be  taken  out  and  sufficient  sand  poured  in  to  bring  them  to 
the  required  level. 

(11)  Jointing  (rectangular  blocks). — The  joints  shall  be  care- 
fully filled  with  a  grout  composed  of  two  parts  of  fine,  sharp,  clean 
sand  and  one  part  of  Portland  cement  of  an  approved  brand. 

(12)  Jointing   (round  blocks). — The    interstices  between  the 
blocks  shall  be  filled  for  a  depth  of  2  inches  from  the  bottom  with 
clean,  screened  gravel,  the  pebbles  of  which  shall  not  be  less  than 
i  inch  nor  more  than  £  inch  in  diameter,  then  hot  paving-cement 
shall  be  poured  in  to  a  depth  of  2  inches  and  sufficient  gravel 
poured  in  to  fill  the  joints  flush  with  the  top  of  the  pavement,  then 
more  paving  cement  poured  in  until  the  joints  are  full  and  will, 
absorb  no  more.     After  which  a  layer  half  an  inch  deep  of  dry, 
starp  sand  will  be  spread  uniformly  over  the  surface  of  the  pave- 
ment. 

The  quantity  of  paving-cement  required  per  square  yard  will 
not  be  less  than  3£  gallons.  This  quantity  must  be  brought  upon 
the  ground,  and  whatever  may  remain  after  the  completion  of  the 
work  will  be  the  property  of  the  city.  Any  wastage  of  paving- 
cement  by  pouring  over  the  surface  instead  of  between  the  blocks, 
must  be  covered  with  a  sufficient  quantity  of  fine  dry  gravel  to 
absorb  it.  The  amount  so  wasted  will  be  estimated,  and  the  quan- 
tity so  estimated  must  be  replaced  by  the  contractor  at  his  own 
expense. 

(13)  Composition  of  Paving -cement. — The  paving-cement  will 
be  composed  of  the  residuum  obtained  from  the  direct  distillation 
of  coal-tar  and  creosote  oil,  in  the  proportion  of  50  gallons  of  oil  to 
1  ton  of  residuum.    The  two  ingredients  will  be  melted  together  in 
suitable  iron  boilers   having  a  capacity  of  not   less   than   1   ton. 
The  cement  shall  be  poured  into  the  joints  when  in  a  boiling  state. 

(14)  Quality  of  the  Gravel. — The  gravel  used  for  filling  the- 
joints  shall  be  free  from  sand,  clay,  or  other  objectionable  SUD- 
stances. 

(15)  Interpretation  of  specifications. 

(16)  Omissions  in  specifications. 

(17)  Engineer  defined. 


WOOD     PAVEMENTS.  147 


(18)  Contractor  defined. 

(19)  Notice  to  contractors,  how  served. 

(20)  Preservation  of  engineer's  marks,  etc. 

(21)  Dismissal  of  incompetent  persons. 

(22)  Quality  of  materials. 

(23)  Samples. 

(24)  Inspectors. 

(25)  Defective  work. 

(26)  Measurements. 

(27)  Partial  payments. 

(28)  Commencement  of  work. 

(29)  Time  of  completion. 

(30)  Forfeiture  of  contract. 

(31)  Damages  for  non-completion. 

(32)  Evidence  of  the  payment  of  claims. 

(33)  Protection  of  persons  and  property. 

(34)  Indemnification  for  patent  claims. 

(35)  Indemnity  bond. 

(36)  Bond  for  faithful  performance  of  work. 

(37)  Power  to  suspend  work. 

(38)  Right  to  construct  sewers,  etc. 

(39)  Loss  and  damage. 

(40)  Old  materials,  disposal  of. 

(41)  Cleaning  up. 

(42)  Personal  attention  of  contractor. 

(43)  Payment  of  workmen. 

(44)  Prices. 

(45)  Security  retained  for  repairs. 

(46)  Payment,  when  made.     Final  acceptance. 

214.  Maintenance  of  Wood  Pavements  by  Contract. — The  con- 
tractor will  undertake  the  maintenance  of  the  pavement  for 
years    (usually    eighteen)    from        day   of  189     .      This 

maintenance  will  consist  in  preserving  the  surface  and  regularity 
of  the  profile,  and  in  making  all  general  or  partial  repairs  neces- 
sary to  keep  the  roadway  in  a  perfect  state,  even  if  the  dilapida- 
tions are  the  result  of  accidental  causes,  as  fires,  sinking  of  the 
subsoil,  etc.,  excepting  only  defects  caused  by  the  digging  of 
trenches. 

The  contractor  will  be  required  to  make  general  repairs  on  all 


US  HIGHWAY    CONSTRUCTION. 

portions  of  the  road  where  there  is:  (1)  A  reduction  of  the  curve 
diminishing  the  original  pitch  by  at  least  one  fourth.  (2)  Where 
the  thickness  of  the  paving-blocks  has  been  worn  away  f  of  an  inch 
or  more.  (3)  Depressions  or  partial  defects  of  the  road  numerous 
enough  to  make  it  rough,  the  engineer  being  judge  of  the  time 
when  it  shall  be  required  for  this  reason. 

The  concrete  foundation  will  generally  be  preserved  by  simply 
adding  Portland-cement  mortar  on  top  if  there  is  room  for  it;  the 
removal  of  the  foundation  is  not  obligatory  except  in  case  of  its  bad 
condition. 

Besides  the  general  repairs  the  contractor  must  insure  the  con- 
stant good  state  of  the  pavement  by  partial  repairs  that  may  be 
necessary.  He  must  immediately  replace  paving-blocks  that  are 
decayed,  crushed,  broken,  or  depressed  by  any  cause  whatever,  also 
those  which  have  become  impregnated  with  urine  or  other  offen- 
sive liquids  and  emit  a  bad  odor. 

He  must  repair  holes  whose  depth  reaches  f  of  an  inch  for  a 
length  of  3  feet  in  any  direction. 

At  the  junction-lines  of  the  wooden  pavement  with  the  stone  or 
asphalt  pavement,  paving-blocks  will  be  replaced  when  they  shall 
have  been  worn  away  -^  °f  an  inch. 

In  all  partial  repairs  the  new  pavement  must  have  the  same 
level  as  the  adjacent  pavement;  no  projections  will  "be  permitted. 
If  any  of  the  defects  enumerated  in  this  article  are  not  repaired 
within  three  days  after  notification,  a  charge  of  dollars  per 

day  will  be  deducted  from  the  contract  price  for  each  day's  delay. 

Renewals  of  the  pavement  over  trenches  opened  for  any  cause 
must  be  executed  in  the  same  time  and  under  the  same  restriction 
as  above.  The  renewed  portions  will  immediately  pass  into  the 
maintenance  of  the  contractor,  who  must  preserve  them  in  accord- 
ance with  the  foregoing  conditions.  No  claims  will  be  allowed  for 
repairs  required  by  sinking  of  the  earth.  The  contractor  will  only 
be  paid  for  the  area  of  the  trenches  measured  when  filled  up. 

The  old  material  and  rubbish  from  repairs  must  be  entirely 
removed  from  the  street  on  completion  of  the  work,  in  default  of 
which  the  contractor  will  be  subjected  to  a  penalty  of 
dollars  per  day  for  each  deposit  not  removed. 

At  the  expiration  of  the  maintenance  period  the  pavement 
must  be  delivered  in  perfect  condition.  Three  months  before  the 


WOOD    PAVEMENTS. 


expiration  of  the  contract  term  the  engineer  will  make  a  statement 
showing  the  condition  of  the  pavement.  The  pavement  shall  not 
be  received  unless  it  satisfies  the  following  requirements:  (1) 
There  must  be  no  holes  having  a  depth  of  f  of  an  inch  in  any 
square  yard  of  the  pavement.  ('2)  The  transverse  contour  of  the 
surface  must  not  at  any  point  be  reduced  so  that  the  rise  is  less 
than  four  fifths  of  its  original  value.  (3)  The  thickness  of  the 
blocks  must  at  no  place  be  less  than  2  inches.  After  the  engin- 
eer's inspection  and  report  the  contractor  will  be  allowed  three 
months  to  place  the  work  in  the  required  condition. 

The  contract  price  fixed  for  the  renewal  of  the  pavement  will 
be  paid  for  the  repairs  over  trenches,  the  demolition  of  the  pave- 
ment being  at  the  expense  of  the  person  or  companies  opening  the 
trench.  The  contractor  must,  if  necessary,  relay  the  pavement 
with  entirely  new  materials,  and  can  make  no  claim  for  damages  to 
the  work  or  its  maintenance. 

The  price  to  be  paid  for  maintaining  the  pavement  in  the  above- 
described  condition  is  cents  per  square  yard,  and  will  be 
payable  quarterly  during  the  contract  period.  Ten  percentum  of 
the  amount  payable  quarterly  will  be  retained  and  shall  not  be  due 
or  payable  until  the  expiration  of  the  contract  period. 

The  price  to  be  paid  per  square  yard  for  the  renewal  of  the 
pavement  over  trenches  is  dollars. 

215.  Specifications  for  Laying  Cedar  Pavement  in  Chicago. — 
Before  paving  the  street  shall  be  graded  to  conform  to  stakes  or 
profiles  to  be  given  by  the  engineer  in  charge,  and  thoroughly 
flooded,  rammed,  and  rolled  to  give  it  a  solid  bed. 

Pawing. — 1st.  The  pavement  shall  not  be  laid  on  any  street 
until  the  material  thereof  shall  have  been  made  firm  and  unyield- 
ing, and  the  contractor  shall  assume  all  the  responsibility  therefor. 

2d.  A  bed  of  clean  lake-shore  sand,  not  less  than  three  (3)  inches 
in  depth,  shall  be  smoothly  and  evenly  spread  over  the  surface  of 
the  street,  and  compactly  rammed  and  rolled  down. 

3d.  A  foundation  of  two-  (2-)  inch  sound  common  hemlock 
plank,  to  be  laid  lengthwise  of  the  street,  close  together  upon  one- 
(1-)  inch  by  eight-  (8-)  inch  pine  stringers  under  the  ends  and 
centres.  Stringers  to  be  firmly  bedded  in  the  sand. 

4th.  Upon  said  foundation  live  cedar  blocks,  free  from  bark  and 
perfectly  sound,  not  less  than  four  (4)  inches  nor  more  than  eight 


150  HIGHWAY   CONSTRUCTION. 

(8)  inches  in  diameter,  and  six  (6)  inches  in  length,  shall  be  placed 
on  end,  close-laid,  resting  properly  on  their  bases  and  well  driven 
together.  All  blocks  more  than  eight  (8)  inches  in  diameter  shall 
be  split  and  the  corners  cut  sufficiently  to  make  good  joints  with 
adjacent  blocks. 

No  split  blocks  of  less  than  three  (3)  inches  in  thickness  will  be 
allowed. 

All  knots  or  excrescences  must  be  cut  off  to  make  the  blocks 
practically  uniform  in  diameter  throughout  their  length. 

No  interstice  between  the  blocks  to  be  more  than  one  and  one- 
half  (1|)  inches  nor  less  than  three  quarters  (f )  of  an  inch. 

No  square  holes  will  be  allowed,  nor  must  two  split  sides  come 
together. 

The  surface  of  the  pavement  must  be  true  and  uniform. 

In  case  any  loose  or  defective  blocks  shall  be  found  in  the  pave- 
ment, they  shall  be  removed  and  replaced  by  perfect  blocks  of 
proper  size,  and  so  much  of  the  pavement  as  may  be  necessary  to 
make  the  work  perfect  shall  be  taken  up  and  relaid  at  the  expense 
of  the  contractor. 

The  blocks  will  be  carefully  inspected  after  they  are  brought  on 
the  line  of  the  work,  and  all  blocks  or  other  material  which,  in 
quality  or  dimensions,  do  not  strictly  conform  with  these  specifica- 
tions, or  which  may  be'  otherwise  defective,  shall  be  rejected,  and 
must  be  immediately  removed  from  the  line  of  the  work  by  the 
contractor.  The  contractor  will  be  required  to  furnish  such  labor- 
ers as  may  be  necessary  to  aid  the  inspector  in  the  examination  and 
culling  of  the  blocks  and  other  material ;  and  in  case  the  contractor 
shall  neglect  or  refuse  so  to  do,  such  laborers  as  in  the  opinion  of 
the  Commissioner  of  Public  Works  may  be  necessary  will  be  em- 
ployed, and  the  expense  incurred  shall  be  deducted  from  any  money 
then  due  or  which  thereafter  may  become  due  the  contractor. 

5th.  The  spaces  between  the  blocks  to  be  filled  with  clean,  dry 
lake-shore  gravel,  of  one  fourth  (£)  to  one  (1)  inch  in  size,  the  pro- 
portion of  said  gravel  to  be  such  as  to  completely  fill  the  interstices, 
and  shall  be  thoroughly  rammed  with  proper  tools  and  by  compe- 
tent and  experienced  help,  and  again  filled  with  the  same  kind  of 
gravel  and  again  thoroughly  rammed. 

In  the  above-described  ramming  the  filling  in  each  interstice 
must  be  struck  three  full  blows  and  driven  down  well.  Two  com- 


WOOD    PAVEMENTS.  151 


petent  rammers  must  be  constantly  employed  after  each  paver. 
No  teams  will  be  allowed  on  the  pavement  before  it  is  properly 
rammed.  After  ramming  the  pavement  will  be  flooded  with  hot 
composition,  not  less  than  one  and  one  half  (1-J)  gallons  per  square 
yard  being  used.  The  tar  will  be  distributed  with  a  three-  (3-) 
gallon  kettle,  the  work  to  be  done  in  sections  as  the  Commissioner 
of  Public  Works,  or  his  representative,  may  direct. 

6th.  After  which  clean,  dry  lake-shore  gravel,  about  one  fourth 
(^)  inch  in  size,  shall  be  spread  over  the  street  in  such  quantity  that 
when  swept  all  the  interstices  between  the  blocks  will  be  thoroughly 
filled.  When  the  gravel  is  put  on  the  second  and  third  time  there 
must  be  enough  space  left  between  the  portions  rammed  once  and 
twice  for  the  other  portions  to  enable  the  inspector  to  see  that 
every  part  of  the  street  is  thoroughly  rammed. 

7th.  The  whole  surface  will  be  swept  over  and  covered  with  hot 
•composition  not  less  than  one  half  (4)  gallon  per  square  yard,  and 
immediately  covered  with  dry  roofing-gravel,  or  gravel  screened 
from  that  used  to  fill  the  spaces  between  the  blocks,  said  covering 
to  be  not  less  than  one  (1)  inch  thick.  All  gravel  used  here  must 
be  lake-shore  gravel,  entirely  free  from  sand  or  pebbles,  over  one 
half  (|)  inch  in  size,  and  dried  and  heated  enough  to  prevent  the 
chilling  of  the  composition.  The  gravelling  and  tarring  must  be 
completed  each  day  to  within  fifteen  (15)  feet  of  the  end  of  the 
paving,  and  the  top  dressing  to  within  fifty  (50)  feet.  If  the  gravel 
and  pavement  becomes  wet  before  the  tarring  is  completed,  the  same 
may  be  ordered  taken  by  the  Commissioner  of  Public  Works. 

The  composition  used  will  be  furnished  by  the  city  in  the  ordi- 
nary portable  tanks  at  some  point  within  the  city  limits;  the  same 
to  be  transferred  by  the  contractor  from  the  receiving  point  to  the 
work,  and  the  empty  tanks  returned  to  the  place  of  reception;  the 
contractor  to  furnish  the  necessary  fuel  and  labor  to  keep  the  com- 
position at  a  temperature  of  not  less  than  300  degrees  Fahrenheit, 
and  be  at  all  times  responsible  for  the  tanks  and  their  contents 
while  in  his  care.  The  Department  reserves  the  right  to  increase 
or  diminish  the  quantity  of  the  composition  used, 

216.  Extracts  from  the  Specifications  for  Laying  Cedar-block 
Pavements  in  Minneapolis.— Street  Railway.— Upon  such  streets  as 
the  street-railway  company  has  tracks,  it  shall  be  the  duty  of  the 
street-railway  company  to  lower  its  tracks  to  the  grade  of  the  pave- 
ment to  be  laid.  The  said  street-railway  company  in  lowering  its 


HIGHWAY    CONSTRUCTION. 


tracks  shall  deposit  the  material  excavated  on  the  outside  of  its 
tracks,  and  the  contractor  will  be  required  to  remove  the  same  at 
the  same  price  per  cubic  yard  as  for  extra  excavation.  It  is,  how- 
ever, expressly  understood  that  when  the  street-railway  company 
has  double  tracks  the  contractor  will  be  required  to  excavate  and 
pave  the  spaces  between  said  double  tracks  in  the  same  manner  as 
the  remainder  of  the  roadway,  and  shall  receive  the  same  price  per 
square  yard  for  said  paving  as  he  shall  receive  per  square  yard  for 
the  remainder  of  the  paving  of  said  roadway. 

Blocks.  —  The  blocks  must  be  of  the  best  quality  of  cedar,  live 
and  perfectly  sound,  and  when  in  place  be  free  from  projecting 
knots  and  bark.  They  must  be  of  a  uniform  length  of  six  (6) 
inches,  and  have  a  diameter  of  not  less  than  four  (4)  inches  nor 
more  than  (10)  ten  inches.  No  blocks  exceeding  ten  (10)  inches  in 
diameter  will  be  allowed  in  the  work  either  whole  or  split,  and 
it  is  hereby  expressly  understood  that  the  contractor  will  not  be 
allowed  to  deposit  upon  the  line  of  the  work  any  blocks  having  the 
diameter  greater  than  ten  (10)  inches,  or  any  blocks  turned  from 
a  post  of  a  greater  diameter  than  ten  (10)  inches. 

It  is  expressly  understood  that  the  contractor  will  be  required 
to  repair  in  a  satisfactory  manner  any  paving  that  may  settle  or 
become  defective  on  account  of  improper  workmanship  or  material, 
or  on  account  of  the  laying  or  construction  of  water-mains,  sewers, 
gas-pipes,  or  making  sewer,  water,  or  gas  connections,  or  conduit- 
laying,  or  any  excavations  allowed  to  be  made  in  the  street  by  the 
city  council,  which  may  have  been  done  previous  to  the  laying  of 
said  pavements,  without  cost  to  the  city  of  Minneapolis. 

Flooring.  —  Upon  the  finished  sub-grade  must  be  laid  a  floor  of 
sound  white-pine  plank,  of  the  quality  equal  to  the  grade  known 
as  first  common  lumber,  as  the  city  engineer  and  the  city  council 
may  determine.  These  plank  must  be  laid  lengthwise  of  the 
street  with  close  joints,  and  be  two  (2)  inches  thick,  from  eight  (8)  to 
twelve  (12)  inches  wide,  and  from  fourteen  (14)  to  sixteen  (16)  feet 
long.  They  must  have  a  bearing  at  each  end  and  in  the  centre  upon 
a  one-  (1-)  inch  by  eight-  (8-)  inch  stringer  firmly  bedded  in  the 
sand.  Planks  not  less  than  six  (6)  inches  wide  may,  however, 
be  used  in  order  to  form  the  crown  of  crossings. 

Laying.  —  The  blocks  must  be  placed  upon  their  ends  in  close 
contact  with  each  other,  on  a  clean  floor.  The  joints  between  the 


WOOD    PAVEMENTS.  153 

blocks  must  not  exceed  two  inches  in  their  longest  direction. 
Blocks  of  less  diameter  than  six  inches  must  not  be  split,  nor  must 
a  piece  of  less  size  than  half  the  block  be  used.  The  corners  of 
split  blocks  must  be  trimmed  so  as  to  make  proper  joints.  Un- 
necessary splitting  of  blocks  will  not  be  allowed. 

Joints  to  be  Filled. — The  joints  or  spaces  between  the  blocks 
must  be  filled  in  the  following  manner:  First,  fill  the  joints  by 
sweeping  clean,  screened  gravel,  the  pebbles  of  which  shall  be  of  a 
size  not  exceeding  one  inch  in  their  largest  diameter,  into  them. 
After  sweeping,  the  surface  of  the  pavement  must  be  clean  and  free 
from  gravel,  then  the  gravel  must  be  thoroughly  tamped.  This 
process  must  be  repeated  a  second  time.  Gravel  of  the  same  kind 
as  before  used  must  be  spread  over  the  surface  to  a  depth  of  not 
less  than  one  inch  above  the  top  of  the  blocks. 

Gutters  and  Corners  of  Crossings  must  be  made  as  follows :  The 
outside  plank  shall  be  3  inches  thick,  16  inches  high,  and  20  feet 
long  on  80-foot  streets,  and  3  inches  by  16  inches  by  16  feet  on  60- 
foot  streets,  and  held  in  place  by  not  less  than  six  posts  of  3  by  6  by 
30  inches,  driven  to  a  depth  of  three  inches  below  the  top  and 
equidistant  along  the  length  of  the  plank.  There  shall  be  a  plank 
2  inches  thick,  10  feet  long,  for  80-foot  streets,  and  2  inches  by  8 
feet  on  60-foot  streets,  and  of  a  width  of  3  inches  less  than  the 
depth  of  the  gutter,  placed  against  the  curb  to  support  the  gutter- 
cover,  which  shall  be  made  of  two  pieces  of  3  by  12  inches  by  10 
feet  on  80-foot  streets,  and  of  3  by  12  inches  by  8  feet  on  60-foot 
streets,  fastened  together  with  four  pieces,  2  by  19  inches,  well 
nailed  with  six  30d.  spikes  to  each  piece.  The  top  of  the  outside 
gutter-plank  on  the  slope  of  the  crossing  shall  be  trimmed  to  con- 
form to  the  top  of  the  paving.  In  making  proposals  the  contractor 
will  state  a  price  which  shall  include  cost  of  excavating  eight  (8) 
inches  below  the  top  of  the  finished  paving;  also  the  furnishing 
and  putting  in  place  complete  of  all  lumber  required  in  the  gutter 
crossings  and  covers.  The  contractor  will  state  a  price  per  cubic 
yard  for  extra  excavation. 

216a.  Microbes  in  Wood  Pavements.— Recent  investigations 
made  in  Europe  regarding  the  sanitary  qualities  of  wood  pave- 
ments are  reported  in  "  Le  Lyon  Medical "  as  follows : 

In  the  superficial  layers  of  a  wood  pavement,  after  it  had  been 
thoroughly  swept  and  washed  with  water,  there  were  found  in  one 


154  HIGHWAY   CONSTRUCTION. 

case  50,000,000  and  in  another  79,360,000  microbes  to  the  gram; 
at  a  depth  of  five  centimeters  in  one  case  51,000,  at  a  depth  of 
six  centimeters  in  another  case  423,600  to  the  gram.  Only  a 
few  of  the  microbes  found  were  liquefying  organisms,  and  in  no 
case  did  they  seem  noxious  when  introduced  by  inoculation  into 
the  circulation  of  guinea-pigs. 

21 6b.  Cedar-block  Pavements.— INDIANAPOLIS,  INC. — Wash- 
ington red  cedar  untreated;  rectangular  blocks;  sand  foundation 
unsatisfactory;  concrete  foundation,  1-inch  sand  cushion  coat; 
blocks  laid  close  together.  After  five  years  shows  considerable 
wear,  while  here  and  there  rotted  blocks  are  visible. 

Red  cedar  treated  with  3  pounds  of  creosote  per  cubic  foot; 
rectangular  blocks  4  inches  wide  and  5  inches  with  the  grain  of 
the  wood;  concrete  foundation,  1-inch  sand  cushion;  blocks  laid  at 
an  angle  of  45°  with  the  axis  of  the  street;  no  provision  for  expan- 
sion; blocks  driven  close  together  with  a  sledge;  joints  filled  as  far 
as  possible  with  paving-pitch. 

Extent  of  wood-block  pavement  in  1899,  209,094  square  yards. 

TORONTO,  CAN. — In  1898, 41.1  per  cent  of  all  the  pavements  in 
the  city  was  cedar  block.  Mr.  Bust,  City  Engineer,  explains  the 
preference  for  this  pavement  as  follows : 

"A  cedar-block  pavement  is  cheap,  easily  laid  and  repaired, 
noiseless,  and — dependent  upon  the  extent  of  the  traffic — will 
remain  in  good  repair  for  from  six  to  eight  years,  and  at  the  end 
of  that  period  it  can  be  renewed  at  a  cost  of  from  45  to  50  cents 
per  square  yard,  making  it  the  cheapest  pavement  that  can 
be  laid." 

216c.  Karri  (Australian)  Block  Pavement.— NEW  YORK,  N.  Y. — 
The  experimental  block  of  Karri  or  Australian  redwood  pavement 
laid  in  1895  on  Twentieth  Street  is  not  considered  a  success,  on 
account  of  its  excessive  slipperiness  in  wet  weather. 

LONDON,  ENG. — The  Australian  hard-wood  blocks  laid  in  1896 
or  earlier  are  reported  as  either  in  "  fair  condition  "  or  "  showing 
signs  of  wear."  "  Outside  the  city  proper  hard-wood  blocks  laid  in 
Tottenham  Court  Road  in  December,  1892,  had  worn  very  unevenly 
by  June,  1899,  besides  which  the  noise  caused  by  the  traffic  was 
very  great,  and  the  pavement  was  being  extensively  repaired." 
(Mr.  J.  D.  Ross,  Engineer  to  the  City  of  London.) 


WOOD    PAVEMENTS.  155 


216d.  Creosoted  Pine  Blocks.— INDIANAPOLIS,  IND.— Material: 
Long-leaf  Southern  pine  treated  with  10  pounds  of  creosote  per 
•cubic  foot. 

Size  of  Hocks :  4  inches  by  4  inches,  and  from  6  to  10  inches 
long. 

Foundation:  Concrete. 

Cushion  coat :  1  inch  of  sand. 

Width  of  joints :  Blocks  laid  close. 

Joint-filling :  Fine  sand  or  paving-pitch. 

Ramming :  Blocks  compacted  by  rolling. 

Expansion-joint :  1  to  2  inches  at  curb  (according  to  width  of 
street),  filled  with  sand  and  covered  with  paving-pitch. 

Surface  of  blocks  covered  with  J  inch  of  clean  coarse  sand  or 
granite  screenings. 

Composition  of  paving-pitch:  10$  of  refined  Trinidad  asphalt 
and  90$  of  coal-tar  distillate. 

Cost  of  construction :  $2.10  to  $2.50,  with  guaranty  for  five  to 
nine  years. 

GALVESTON,  TEX. — Material :  Yellow  pine  impregnated  by  the 
vacuum  process  with  12  pounds  creosote  per  cubic  foot. 

Size  of  blocks :  5  inches  wide,  5  inches  deep,  10  inches  long. 

Foundation :  The  natural  sandy  soil,  compacted  by  saturating 
with  water  and  shaped  to  the  required  form. 

Joint-filling :  Sand. 

Width  of  joints :  Close. 

Ramming :  By  hand-rammers. 

Surface  is  flooded  with  coal-tar  sufficiently  fluid  to  permeate 
the  joints,  followed  by  a  coating  composed  of  asphaltic  paving- 
oement  or  asphtiltum  and  dead-oil,  after  which  the  surface  is  cov- 
ered with  a  thin  layer  of  sand. 

216e.  Cottonwood  and  Gum  Blocks.— ST.  Louis,  Mo.— Gum 
and  cottonwood  blocks  impregnated  with  chloride  of  zinc;  concrete 
foundation  6  inches  thick;  joints  filled  with  bituminous  paving- 
cement.  Burnettized  cottonwood  used  on  Broadway  developed 
decay  in  the  third  year. 

216f.  Redwood  Block  Pavement.— OAKLAND,  CAL.— Rectangu- 
lar blocks  4  inches  by  6  inches  by  6  inches  cut  from  seasoned  butt- 
cut  redwood  and  boiled  in  asphalt;  foundation  6  inches  concrete, 


15G  HIGHWAY    CONSTRUCTION. 

surface  of  which  is  painted  with  hot  asphalt;  blocks  laid  close  in 
rows  at  right  angles  to  axis  of  street;  joints  filled  with  asphalt,  and 
surface  covered  with  a  coat  of  asphalt  T^-  inch  thick.  The  asphalt 
coat  is  designed  to  be  the  wearing  surface  and  to  be  renewed  as 
often  as  necessary. 

It  is  said  that  this  pavement  has  given  satisfaction  during  three 
years'  service  in  San  Francisco. 

21 6g.  Jetley's  Patent.* — The  wood  blocks  are  compressed  to- 
gether by  machinery  in  slabs  4  feet  6  inches  long  and  12  inches 
wide.  These  slabs  are  laid  directly  upon  the  compacted  earth  sur- 
face, and  when  the  surface  exposed  to  traffic  becomes  worn  they 
can  be  turned  over,  presenting  a  new  surface  to  the  traffic. 

The  Jetley  system  is  the  most  recent  contribution  to  the 
numerous  inventions  for  the  improvement  of  wood  pavements;  it 
has  been  tried  in  London  with,  it  is  said,  satisfactory  results;  but 
it  seems  strange,  in  view  of  past  experiences,  to  hear  any  one  advo- 
cating the  laying  of  a  pavement  directly  upon  the  earth. 

*  Engineering  News,  vol.  xliii.  p.  409. 


CHAPTER  V. 
ASPHALTUM  AND  COAL-TAR  PAVEMENTS. 

217.  Asphalt  was  first  employed  for  street-paving  in  Paris  in 
1838,  but  it  was  not  employed  to  any  great  extent  until  1'854.     In 
1869  it  was  introduced  into  London,  and  since  then  has  been  ex- 
tensively used  throughout  Europe. 

The  success  which  attended  this  pavement  led  to  its  introduc- 
tion into  America.  The  great  cost  of  importing  the  materials  from 
Europe  made  the  pavement  so  expensive  as  to  induce  American 
inventors  to  seek  to  manufacture  a  material  which  should  have 
similar  qualities.  The  result  was  the  introduction  of  many  sub- 
stitutes and  imitations,  the  majority  of  which  proved  defective. 

The  great  cost  of  the  imported  material  and  the  failure  of  the 
substitutes  directed  attention  to  the  deposits  of  natural  bitumen  on 
the  island  of  Trinidad,  which  could  be  brought  here  very  cheaply. 
Experiments  were  made  which  demonstrated  the  possibility  of  mak- 
ing a  mastic  with  Trinidad  bitumen  as  its  cementing  material,  as 
strong,  elastic,  and  durable  as  that  imported  from  Europe;  but  it 
was  only  after  some  years  that  this  process  was  introduced  and  made 
a  commercial  success. 

218.  The  difference  between  the  asphalt  pavements  of  Europe 
and  those  of  America  is  due  to  the  character  of  the  materials.     The 
former  are  composed  of  limestone  rock  naturally  impregnated  with 
bitumen,  while  the  latter  are  composed  of  an  artificial  mixture  v£ 
bitumen,   limestone,  and   sand.     The  limestone  in  the  European 
pavements  becomes  hard,  smooth,  and  slippery  under  traffic,  and 
is  thus  objectionable  for    general   use   in  frosty  latitudes.     The 
granular  nature  of  the  sand  used  in  preparing  the  Trinidad  asphal- 
tum  diminishes  the  tendency  to  wear  smooth  and  materially  lessens 
the  slipping  of  horses. 

219.  Although  many  deposits  of  bituminous  rock  are  found  in 
the  United  States,  they  have  been  used  only  to  a  limited  extent, 

157 


158 


HIGHWAY   CONSTRUCTION. 


and  the  island  of  Trinidad  continues  to  be  the  main  source  of  supply 
for  the  United  States.  This  is  due  entirely  to  its  advantage  in  cost 
of  transportation.  The  railroad  freight  rates  from  the  place  of  the- 
deposits  practically  shut  out  the  bituminous  rock  of  California  and. 
Kentucky  from  competition  in  the  Eastern  States,  and  a  similar 
condition  may  be  said  to  affect  the  sale  of  Trinidad  asphaltum  in 
the  cities  of  Europe,  since  the  bituminous  limestones  of  Val  de- 
Travers  and  Seyssel,  having  the  advantage  in  freights,  control  the- 
markets. 

220.  The  cost  of  preparing  the  different  varieties  of  asphaltum 
for  street  pavement  is  nearly  the  same;  and  as  all  appear  to  be  about 
equally  durable,  the  exclusive  use  of  any  one  of  them  is  due  merely 
to  the  advantage  in  freights. 

TYPE-SECTIONS  OF  ASPHALT  PAVEMENTS. 


H" ASPHALT  2" 
BINDER     //2 

COMCflCTE S 


FIG,  14.    HEAVY-TRAFFIC  PAVEMENT. 


ASPHALT 2~ 
CONCRETE** 


FIG,  15,    LIGHT-TRAFFIC  PAVEMENT, 


ASPHALTUM   AND    COAL-TAR    PAVEMENTS. 


139 


'  ASPHALT 2." 
3//VD£f1  I /a 
STONE  BLOCK 


FIG.  15A.  ASPHALT  ON  STONE  BLOCKS. 


x  '^M^^^w^  wwww't'ww  ^/w, 


>    f/"/'"  \\\W/  /7/.( 

FIG,  15s,    ASPHALT  ON    MACADAM. 

221.  The  Advantages  of  Asphalt  may  be  summed  up  as  follows: 

(1)  Ease  of  traction. 

(2)  It  is  comparatively  noiseless  under  traffic. 

(3)  It  is  impervious. 

(4)  It  is  easily  cleansed. 

(5)  It  produces  neither  mud  nor  dust. 

(6)  It  is  pleasing  to  the  eye. 

(7)  It  suits  all  classes  of  traffic. 

(8)  There  is  neither  vibration  nor  concussion  in  travelling  over  it. 

(9)  It  is  expeditiously  laid,  thereby  causing  little  inconvenience 
to  traffic. 

(10)  Openings  to  gain  access  to  underground  pipes  are  easily 
made. 

(11)  It  is  durable. 

(12)  It  is  easily  rapaired. 

222.  Defects  of  Asphalt  Pavement. 

(1)  It  is  slippery  under  certain  conditions  of  the  atmosphere. 


1GO  HIGHWAY    CONSTRUCTION. 

The  American  asphalts  are  much  less  so  than  the  European  on 
account  of  their  granular  texture,  derived  from  the  sand.  The 
difference  is  very  noticeable :  the  European  are  as  smooth  as  glass, 
while  the  American  resemble  fine  sand-paper. 

(2)  It  will  not  stand  constant  moisture,  and  will  disintegrate  if 
excessively  sprinkled. 

(3)  Under  extreme  heat  it  is  liable  to  become  so  soft  that  it 
will  roll  or  creep  under  traffic   and  present  a  wavy  surface,  and 
under  extreme  cold  there  is  a  danger  that  the  surface  will  crack 
and  become  friable.     (In  Washington,  D.  C.,  with  a  range  of  tem- 
perature from  5  to  150  degrees  Fahr.,  no  serious  trouble  has  been 
experienced  with  the  Trinidad  asphalts.) 

(4)  It  is  not  adapted  to  grades  steeper  than  2-J  per  cent.     In 
the  city  of   New  York  there  are  streets  paved  with   asphalt   on 
which   the   grade   varies   from    2  to  6  per  cent,   and  Mr.  North, 
C.E.,  states  that  the  traffic  has  deserted  Ninety-third  Street,  which 
is  paved  with  granite  on  a  grade  of  5.15  per  cent,  for  Ninety-fourth 
Street,  which  is  paved  with  asphalt  on  a  6  per  cent  grade.     (See 
also  Art.  261.)* 

(5)  Repairs  must  be  quickly  made,  for  the  material  has  little 
coherence,  and  if,  from  irregular  settlement  of  the  foundation  or 
local  violence,  a  break  occurs,  the  passing  wheels  rapidly  shear  off 
the  sides  of  the  hole,  and  it  soon  assumes   formidable  dimensions. 
In  London  this  is  prevented  by  constant  watchfulness.     Workmen 
are  employed  to  traverse  the  street  with  a  light  repairing  outfit, 
and  whenever  a  defect  is  observed  it  is  patched  at  once,  and   so 
effectually  that  the  spot  cannot  be  distinguished. 

223.  The  strewing  of  sand  upon  asphalt  renders  it  less  slippery; 
but  in  addition  to  the  interference  of  the  traffic  whilst  this  is  being 
done,  there  are  further  objections,  viz.,  the  possible  injury  by  the 
sand  cutting  into  the  asphalt,  the  expense  of  labor  and  materials, 
and  the  mud  caused  thereby  which  has  afterwards  to  be  removed. 

224.  Although  pure  asphaltum  is   absolutely  impervious   and 
insoluble  in  either  fresh  or  salt  water,  yet  asphalt  pavements  in  the 
continued  presence  of  water  are  quickly  disintegrated.     Ordinary 
rain  or  diiily  sprinkling  does  not  injure  them  when  they  are  allowed 

*  James  Street,  Syracuse,  N.  Y.,  is  paved  with  asphalt  on  a  7.30  per  cent 
grade. 


ASPHALTUM   AND    COAL-TAR   PAVEMENTS.  161 

to  become  perfectly  dry  again.  The  damage  is  most  apparent  in 
the  gutters  and  adjacent  to  overflowing  drinking-fountains.  This 
defect  has  long  been  recognized,  and  various  measures  have  been 
taken  to  overcome  it,  or  at  least  to  reduce  it  to  the  minimum.  In 
some  cities  ordinances  have  been  passed  seeking  to  regulate  the 
sprinkling  of  the  streets,  and  in  many  places  the  gutters  are  laid 
with  stone,  while  in  others  the  asphalt  is  laid  to  the  curb  and  a 
space  of  12  to  15  inches  along  the  curb  is  covered  with  a  thin  coat- 
ing of  asphalt  cement.  Vitrified  brick  has  been  used  for  the 
gutters  of  streets  paved  with  sheet  asphalt.  Regarding  the  use  of 
this  material  in  Washington,  D.  C.,  the  Report  of  the  Engineers* 
Department  for  1899  says: 

"  The  use  of  brick  gutters  for  sheet-asphalt  pavements  has  been 
continued,  and  the  experience  of  the  office  leads  to  the  conclusion 
that  this  -form  of  construction  is  decidedly  better  than  laying 
asphalt  to  the  curb.  The  first  gutters  of  this  material  were  laid 
with  the  brick  toothed  into  the  asphalt.  This  practice,  however, 
was  discontinued,  and  the  gutters  have  been  laid  since  with  con- 
tinuous joints.  The  latter  construction  has  been  found  to  be 
much  better  than  the  toothed  method,  as  it  has  been  demonstrated 
by  several  years'  experience  that  it  is  impossible  to  sufficiently 
compact  the  asphalt  between  the  teeth  to  prevent  water  entering, 
thus  producing  early  decay  or  breaking  up  of  the  asphalt.  With 
continuous  joints  it  is  possible  to  run  the  roller  up  to  and  along  the 
very  edge  of  the  brick,  producing  as  much  compaction  at  this  point 
as  on  other  portions  of  the  street.  It  has  been  observed  in  the 
cases  of  gutters  of  the  two  classes  laid  about  the  same  time  that  in 
the  toothed  gutter  the  asphalt  between  the  teeth  and  immediately 
adjacent  thereto  is,  in  a  number  of  cases,  already  beginning  to 
show  signs  of  breaking  up,  while  the  asphalt  adjacent  to  the  con- 
tinuous-joint gutter  is  apparently  as  good  as  ever." 

It  is  said  that  the  pavements  formed  of  asphalt  cement  in  whicli 
"maltha,"  or  liquid  asphalt,  is  used,  instead  of  the  residuum  of 
petroleum,  as  the  fluxing  agent,  are  not  affected  by  moisture. 

Investigations  *  made  to  ascertain  the  action  of  water  on  asphalts 

*  By  Messrs.  G.  C.  Wbipple  aud  D.  D.  Jacksou  at  Mt.  Prospect  Labora- 
tory, Brooklyn,  N.  Y.  Paper  read  before  Brooklyn  Engineers'  Club,  March 
8,  1900. 


162  HIGHWAY    CONSTRUCTION. 

show  that  some  asphalts  are  acted  upon  to  a  considerable  extent,, 
while  others  are  apparently  unaffected;  that  the  action  varies  with 
the  character  of  the  water.  Distilled  water  and  waters  containing 
the  smallest  amounts  of  mineral  matter  produced  the  greatest 
action.  Sea-water  gave  but  little  action,  and  a  concentrated  solu- 
tion of  brine  showed  no  action. 

The  action  of  the  water  was  exhibited  by  a  change  in  color 
from  black  to  brown,  and  in  condition  from  hard  to  soft  and 
punky,  with  the  surface  covered  with  cracks  and  pits. 

The  softening  action  penetrated  to  depths  ranging  from  00  to 
1.3  millimeters  with  distilled  water  and  00  to  1.1  millimeters  with 
surface  and  ground  water. 

The  amount  of  soluble  matter  extracted  from  the  asphalt  corre- 
sponded with  the  intensity  of  the  action  of  the  water;  distilled 
water  showed  the  greatest  action  and  took  up  the  largest  amount  of 
soluble  matter.  The  amount  ranged  from  2.83  to  21.42  per  cent. 
The  mineral  constituents  given  up  were  sodium  chloride,  carbon- 
ates and  sulphates  of  calcium  and  magnesium,  and  oxide  of  iron. 
Some  of.  the  samples  yielded  both  mineral  and  organic  soluble 
matter. 

All  the  samples  showed  an  increase  in  weight  which  varied  with 
the  condition  of  exposure. 

The  greatest  increase  was  observed  in  the  case  of  Trinidad 
asphalt.  The  sample  exposed  in  Mt.  Prospect  reservoir  gained 
3.92  grams  per  square  metre  in  one  day;  after  two  months  it  had 
gained  31.24  grams;  in  the  conduit  at  Freeport  the  gain  during 
two  months  was  84.41  grams;  in  Mt.  Prospect  stand-pipe,  where- 
the  pressure  was  great,  the  gain  was  137.09  grams,  equivalent  to- 
4028  per  square  yard  of  exposed  surface.  The  gain  in  weight  of 
the  other  samples  was  less,  but  corresponded  in  a  general  way  with 
the  amount  of  action  observed. 

"  The  cause  of  the  action  of  water  upon  asphalt  appears  to  be 
in  part  chemical  and  in  part  physical. 

"  The  action  of  water  upon  asphalt  is  due  to  the  unsaturated  na- 
ture of  the  hydrocarbons  present,  and  is  attended  by  a  partial  solu- 
tion of  the  asphalt  in  the  water.  There  is  also  a  loss  of  sulphur  as 
hydrogen  sulphide,  and  an  increase  in  weight  of  the  asphalt  itself,, 
due  to  oxidation  and  to  the  mechanical  admixture  of  water.  By 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS. 


163 


far  the  most  important  action  which  occurs  is  that  produced  by 
this  oxidation  of  the  asphalt  by  means  of  the  dissolved  oxygen  in 
the  water." 

"  The  following  asphalts  and  fluxes  are  arranged  in  the  order 
of  least  to  greatest  action  by  water:  Petroleum  residuum;  Assyrian 
asphalt;  Asphaltina;  Cuban  asphalt;  Alcatraz  maltha  No.  2;  Alca- 
traz  maltha  No.  1;  Alcatraz  asphalt  D;  Alcatraz  asphalt  XX;  Ber- 
muda asphalt;  Trinidad  asphalt. 


FIG.  15c, 


ASPHALT 


BRICK   GUTTER 


FIG.  15D. -ASPHALT  WITH    BRICK  GUTTER. 


225.  Asphalt  laid  adjoining  centre-bearing  street-car  rails  is 
quickly  broken  down  and  destroyed.  This  defect  is  not  peculiar 
to  asphalt.  All  other  materials  when  placed  in  similar  positions 
are  quickly  worn.  Granite  blocks  laid  along  such  tracks  have  been 
cut  into  at  a  rate  of  more  than  half  an  inch  a  year.  The  frequent 
entering  and  turning  off  of  vehicles  from  car-tracks  is  one  of  the 
severest  tests  that  can  be  applied  to  any  paving  material;  moreover, 
the  gauge  of  trucks  and  vehicles  is  frequently  greater  than  that  of 


164  HIGHWAY    CONSTRUCTION. 

the  rails,  so  one  wheel  runs  on  the  rail  and  the  other  outside.  The 
number  of  wheels  thus  travelling  in  one  line  must  quickly  wear  a 
rut  in  any  material  adjoining  the  centre-bearing  rail. 

To  obviate  the  destruction  of  asphalt  in  such  situations  it  is 
usual  to  lay  a  strip  of  granite  block  or  brick  paving  alongside  the 
rail.  This  pavement  should  be  of  sufficient  width  to  support  the 
wheels  of  the  widest  gauge  using  the  street. 

The  burning  of  leaves  or  making  of  fires  on  asphalt  pavements 
should  not  be  permitted,  as  it  injures  the  asphalt,  and  the  paving 
companies  cannot  be  compelled  to  repair  the  damaged  places  with- 
out compensation. 

226.  Asphalt  Pavement  Injured  by  Illuminating-gas. — The 
asphalt  pavements  on  some  of  the  streets  of  Frankfort,  Germany, 
became  friable  and  porous.  City  Engineer  Dehnhardt  attributed 
this  to  the  escape  of  illuminating-gas.  This  view  was  ridiculed  by 
several  German  authorities  on  this  material.  The  pavements  were 
taken  up,  and  it  was  found  that  the  gas-pipes  had  several  leaks 
under  the  worst  parts  of  the  street.  Some  of  the  injured  pavement 
and  pieces  of  sound  pavement  were  tested.  The  sound  fragments 
were  placed  in  a  tube  through  which  gas  was  allowed  to  flow. 
After  a  week  the  samples  were  reduced  to  the  same  friable  condition 
in  which  parts  of  the  pavement  had  been  found.  The  samples 
after  several  weeks'  exposure  to  the  atmosphere  regained  their 
original  good  condition.  The  explanation  offered  is  that  a  portion 
of  the  carburetted  hydrogen  of  the  gas  is  absorbed  by  the  asphalt, 
thus  destroying  its  cohesion. 

Regarding  the  destruction  of  asphalt  pavements  by  illuminating- 
gas,  Mr.  A.  W.  Dow,  Inspector  of  Asphalts  and  Cements,  District 
of  Columbia,  in  his  report  for  1898,  says: 

"  As  it  has  been  doubted  by  some  that  this  disintegration  is 
really  due  to  illuminating-gas,  I  have  made  a  most  thorough  investi- 
gation of  the  subject,  and  believe  have  positively  proven  that  gas 
is  the  cause.  Samples  of  pavements  were  obtained  from  several 
affected  spots,  and  in  all  cases  I  have  been  able  to  obtain  from 
them  a  gas  that  exploded  by  passing  an  electric  spark  after  mixing 
with  air.  The  method  employed  to  obtain  the  gas  from  samples  of 
the  surface  mixture  was  by  heating  them  under  boiling  water  and 
collecting  the  gas  given  off  in  an  inverted  funnel.  .  .  .  Two  sam- 


ASPHALTUM   AND    COAL-TAR   PAVEMENTS.  165 

pies  of  a  pavement  were  taken,  one  from  an  affected  spot,  and  the 
other  from  a  good  portion  of  the  pavement  about  ten  feet  away. 
These  samples  were  treated  under  boiling  water  until  they  ceased 
to  evolve  gas.  The  affected  sample  gave  several  times  more  gas 
than  did  the  other.  On  testing,  the  gas  from  the  good  sample  was 
found  to  consist  of  oxygen  and  nitrogen,  which  was  evidently  just 
the  air  from  the  voids  in  the  pavement.  The  gas  from  the  affected 
piece  gave  on  analysis  the  results  shown  in  column  I  of  the  follow- 
ing table."  For  comparison  the  composition  of  illuminating-gas  is 
given  in  column  II. 

i.  H. 

Gas  from  Pavement.    Illuminating-gas. 
Per  Cent.  Per  Cent. 

Carbon  dioxide 8.4  0.2 

Oxygen 10.8  0.0 

Heavy  hydrocarbons 13.4  12.1 

Carbon  monoxide 0.7  25.5 

Hydrogen 6.6  39.2 

Methane 2.0  23.0 

Nitrogen 58.1  0.0 

The  composition  of  the  gas  obtained  from  the  disintegrating 
pavement  does  not  correspond  to  that  of  a  natural  or  marsh  gas, 
sewer-gas,  or  air;  hence  the  only  gas  it  can  be  compared  with  is 
illuminating-gas,  the  analysis  of  which  is  given  in  column  II  of 
the  preceding  table. 

"  On  comparing  the  composition  of  the  gas  given  off  from  the 
disintegrating  pavement  with  the  illuminating-gas,  it  is  seen  that 
they  are  not  at  all  similar  in  composition.  At  first  glance  it  would 
not  seem  possible  that  the  former  gas  could  originate  from  the 
latter,  but  when  the  properties  of  asphalt  are  considered  it  is  easily 
explained. 

"Heavy  hydrocarbons,  to  which  class  asphalts  belong,  are  known 
to  absorb  other  gaseous  hydrocarbons:  the  heavier  the  gas  the  more 
affinity  between  it  and  the  heavy  hydrocarbons.  Knowing  this, 
the  ingredients  of  the  illuminating-gas  that  asphalt  would  have  the 
greatest  affinity  for  would  be  the  heavy  hydrocarbon  gases,  a  slight 
affinity  for  the  marsh-gas  or  methane,  and  no  affinity  for  any  of  the 
other  ingredients.  If  we  examine  the  ingredients  of  the  gas  from 
the  affected  pavement,  it  will  be  found  to  consist  of  some  carbon 


166  HIGHWAY   CONSTRUCTION. 

dioxide,  air  that  was  in  the  voids  and  cracks  of  the  pavement,  and 
the  constituents  of  illuminating-gas  with  the  heavy  hydrocarbon 
gases  very  much  in  excess,  which  is  what  we  would  expect.  To 
practically  demonstrate  that  the  above  takes  place  when  asphalt  is 
in  contact  with  illuminating-gas,  I  took  two  samples  of  gas  from  a 
tap  in  the  laboratory.  One  was  analyzed,  while  the  other  was  kept 
for  several  weeks  in  a  tube  the  interior  of  which  was  coated  with 
asphalt  cement,  such  as  is  used  in  pavements,  after  which  it  was 
analyzed.  The  results  of  the  two  analyses  are  given  in  the  follow- 
ing table : 

Original  Gas.        Gas  after  Asphalt 
Per  Cent.  Absorption. 

Per  Cent. 

.  Carbon  dioxide 0.2  0.1 

Oxygen 0.0  0.0 

Heavy  hydrocarbons 12.1  7.2 

Carbon  monoxjde 25.5  27.3 

Hydrogen 39.2  42.2 

Methane 23.0               .       23.2 

Nitrogen 0.0  0.0 

"  It  is  evident  from  this  that  the  asphalt  cement  has  absorbed 
over  5  per  cent  of  the  heavy  hydrocarbon  gases,  a  little  methane, 
and  practically  nothing  else. 

"  I  have  ascertained  by  experiment  that  one  part  by  volume  of 
asphalt  cement  will  absorb  forty-two  parts  of  illuminating-gas  in 
somewhat  over  a  month.  I  have  also  practically  shown  that 
asphalt  is  much  softened  by  absorbing  gas,  the  ordinary  asphalt 
cement  becoming  as  soft  as  a  thick  maltha  after  being  in  an  atmos- 
phere of  illuminating-gas  for  several  months.  As  to  the  quantity 
of  gas  contained  in  the  affected  pavements,  this  of  course  varies, 
but  in  one  instance  1000  c.c.  of  pavement  gave  off  500  c.c.  of  gas." 

There  is  but  one  remedy  for  the  disintegration  caused  by  gas 
and  that  is  to  stop  the  leak  of  gas. 

227.  Durability. — The  systems  adopted  for  the  maintenance  of 
asphalt  pavements  render  it  difficult  to  ascertain  their  actual  life 
under  traffic.  They  are  repaired  immediately  they  need  it,  and  as 
each  repair  is  so  much  new  material  laid,  the  whole  surface  is 
really  relaid  in  the  course  of  years.  Col.  Haywood  states  that  in 
his  opinion  asphalt  will  last  without  extensive  repairs  from  four 


ASPHALTUM   AND    COAL-TAR   PAVEMENTS.  167 

to  six  years,  and  that  in  the  course  of  ten  years  the  entire  surface 
will  have  been  renewed. 

228.  That  asphalt  successfully  sustains  an  enormous  traffic  is 
shown  by  the  following  figures:   From  London,  Cheapside  has  a 
traffic   of   13,772  vehicles   in   24   hours;    Mansion   House   Street, 
23,332   vehicles   in   24   hours.      Oornhill,   Holborn   Viaduct,   and 
many  others  have  a  daily  traffic  of  upwards  of  12,000  vehicles. 
These  streets  are  paved  with  asphalt. 

229.  There  are  no  streets  in  America  or  elsewhere  in  the  world 
that  have  so  much  traffic  as  the  above-mentioned  London  streets. 
Among  the  vehicles  that  travel  on  them  are  omnibuses  loaded  with 
passengers  inside  and  out,  light  vehicles  of  all  descriptions,  carts, 
carriages,  and  brewery  trucks  loaded  with  tons  of  ale  and  porter. 

The  first  asphalt  pavement  was  laid  in  the  city  of  London  in 
1869,  on  Threadneedle  Street,  adjacent  to  the  Bank  of  England, 
and  was  renewed  at  the  end  of  17  years.  Asphalt  has  lasted  on 
Holborn  Viaduct  17  years,  on  London  Wall  20  years,  in  Loth- 
bury  23  years,  and  in  Princess  Street  22  years;  in  many  of  the 
minor  streets  it  has  lasted  30  years. 

Cheapside  was  paved  in  1870,  and  the  pavement  remained  in 
•constant  tise  for  19  years,  with  of  course  extensive  repairs;  but  up 
to  1889  the  carriageway  was  never  closed  entirely  for  a  general 
relaying  of  the  pavement.  In  1889,  the  contract  for  maintenance 
of  the  asphalt  having  expired,  a  new  contract  was  made  and  a  new 
surface  of  asphalt  was  laid. 

Most  of  the  main  thoroughfares  of  the  old  city  of  London  are 
paved  with  asphalt,  under  17-year  maintenance  contracts. 

230.  St.  Louis,  Mo.—"  The  asphalt  laid  on  Pine  Street  in  1883 
is  now  in  good  condition  after  a  test  of  eight  years  under  a  mixed 
traffic  of  3000  vehicles  in  12  hours  from  7  A.M.  to  7  P.M.     The  work 
was  carefully  executed,  and  consists  of  a  6-inch  hydraulic-cement 
concrete  base,  |-inch  cushion-coat   and   2-inch   surface  or    wear- 
ing   coat;    cross-section    camber  0.50;    width    between    curbs    36 
feet.     Traffic  is  what  may  be  termed  building  materials,  residence 
supplies,  and  suburban.     While  it  has  been  subjected  to  the  heavi- 
est loads  hauled  in  the  city  with  fair  results,  it  must  stand  below 
granite  for  wear/7     (Report  of  Mr.  T.  H.  Macklind,  District  En- 
gineer.) 


168  HIGHWAY    CONSTRUCTION. 

231.  Wear. — Asphalt  is  to  a  certain  extent  elastic  and  does  not 
begin  to  wear  until  this  elasticity  is  overcome  by  thorough  com- 
pression.    This  is  the  case  with  no  other  paving  material.     Stone 
and  wood  begin  wearing  from  the  day  traffic  commences.     Under 
ordinary  traffic  it  may  be  estimated  that  it  will  take  two  years  to 
complete  the  compression  of  asphalt,  and  the  weight  of  a  square 
foot  of  this  pavement  will  at  the  expiration  of  that  time  be  nearly 
the  same  as  on  the  day  it  was  laid,  though  the  thickness  is  reduced 
during  the  first  two  years  as  much  as  it  will  be  in  the  following 
eight.     The  extent  to  which  the  thickness  has  been  reduced  is  said 
to  be  as  much  as  one  fourth  the  original  thickness. 

A  pavement  in  Paris  which  had  lost  more  than  one  fourth  of 
its  thickness  was  found  to  have  Lost  only  5$  of  its  weight  after  IS 
years'  use. 

The  pavement  in  Cheapside,  London,  after  fourteen  years'  use, 
shows  a  reduction,  where  not  repaired,  from  its  original  thickness 
of  2J  to  If  inches. 

232.  Cost  of  Construction. — The  cost   of  construction   varies 
with  the  locality,  thickness  of  wearing  surface,  and  kind  of  founda- 
tion. 

Table  XXXV  shows  the  extent  and  cost  in  several  cities  in 
America. 

In  London  the  first  cost  is  from  $3.75  to  $4.50  per  square  yard, 
including  maintenance.  The  total  annual  expense  varies  from  33. 
to  57  cents  per  square  yard. 

In  Omaha,  Neb.,  the  first  cost  per  square  yard,  including  main- 
tenance for  five  years,  is  about  $2.98. 

The  prices  per  square  yard  given  in  Table  XXXV  for  American 
cities  includes  in  nearly  all  cases  the  maintenance  of  the  pavement 
for  a  period  of  five  years. 

The  extent  of  the  asphalt  pavement  in  use  in  1890  was:  United 
States,  6,803,054  square  yards,  equal  to  446  miles  of  roadway  26  feet 
wide;  Europe,  1,698,846,  equal  to  111.3  miles. 

233.  Cost  of  Maintenance. — Asphalt  pavements   are  generally 
maintained  by  the  companies  that  construct  them.     The  systems 
adopted  are  as  follows: 

The  company  constructing  the  pavement  undertake  to  maintain 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS. 


169 


TABLE  XXXV. 

EXTENT  AND  COST  OF  ASPHALT  PAVEMENT  IN  THE  PRINCIPAL  CITIES  OP 
THE  UNITED  STATES,  1898-99. 


Square 
Yards. 

Cost  of  Con- 
struction 
per  Sq.  Yd. 

Kind  of 
Asphalt. 

Guaranty 
Period 
Years. 

Akron   O          ...          

8,800 
164,133 

555,559 

105,842 
35,728 
1,000 

51,398 
638,135 

117,290 

210,388 
35,000 

3,900,631 

16,424 
96,546 
17,130 
78.890 
1,335,000 

406,700 

130,240 

335,577 
74,567 

349,106 
371,684 

470,925 
100 
17,596 

199,974 

46,933 
2,142 

117,201 
89,566 
90,516 

$3.08 
2.75  ) 
'      1.67  f 
2.58 
2.08 

I     2.63  ) 
1     2.58  f 
(     2.70  I 
1     2.25   [ 
j     2.69   I 
1     1.69  f 
3.00 
2.18 
j    2.67  ) 

i  sis  j: 

3.00 
1.95 
2.56 

f     2.78  ) 
)     2.89   f 
(     2.95   I 
\     1.66  t 
2.25 
3.09 
j     2.07  I 
1     2.30   J 
2.62   ) 
'{     2.30   f 
j     2.48  1 
1     1.90  f 

j     2.69  ) 
1     2.29  [ 
j     2.45   ) 
i     1.80  f 

1.60   { 
1.40   f 
2.40  ) 
1.77  f 
2.65   ) 
2.35   J 

T* 

T,  B,  &  S 

T 
T 

T 
T&A 

T&A 

T&S 

T,K,G,&S 

T 

Block 
T 

T,TX,B&A 

T 

T,  K,  &U 
T 

T 
T,  T',  &  A 
T,  A,  B 

T 

T,  A 
T,  C,  U 
T,  Block 

5  and  7 
10 

5 

5  and  10 
5 

5  and  10 
5 

5 
5 

5  and  10 
10 

10 
5 

Albany   N  Y  

Auburn   N  Y  

Binghamton,  N.  Y  

Buffalo,  N.  Y  

Cambridge  Mass  .  . 

Cleveland,  O  

Dayton,  O  

Elmira  N.  Y  

Erie   Pa  

Fall  River  Mass        

Fort  "\Vayne  Ind              

*  For  explanation  of  symbols,  see  p.  172. 

170 


HIGHWAY   CONSTRUCTION. 


TABLE  XXXV.— Continued. 

EXTENT  AND  COST  OF  ASPHALT  PAVEMENT  IN  THE  PRINCIPAL  CITIES  OP 
THE  UNITED  STATES,  1898-99. 


Square 
Yards. 

Cost  of  Con- 
struction 
per  Sq.  Yd. 

Kind  of 
Asphalt. 

Guaranty 
Period. 
Years. 

Hartford,  Coim  

m*77 

(   $2.55  ) 

TA 

Hoboken   N  J  

Q^  000 

\     2.70  f 

1     ^1 

>   » 

TM    A 

1  Q  fifi(i 

o  7* 

Rlnrk 

Houston,  Tex  

10  Q1A 

Indianapolis,  Ind  ,  

GOfi  795 

j     1.75 

TT5 

1  7Q  ^*>o 

|     3.0 
j    2.73 

>  ** 

TT'    C 

Joliet,  111  

9  695 

\     1.65 

Kansas  City,  Kans.  

64  000 

Kansas  City  Mo  

1  1  9Q  427 

(     2.54  ) 

TA  "R 

1ft 

21  728 

}     2.06  f 
2  50 

Lincoln,  Neb  

5  884 

Los  Angeles,  Cal  

142  850 

1  80 

c 

175  Q4o 

2  00 

T  K"  d  TT 

K  on/1  1ft 

18  442 

2  65 

Manchester,  N.  H  

50  356 

Milwaukee,  Wis  

153  856 

(     2.30  ) 

T 

R 

199  978 

"j     2.12 
\     2.49 

T   TJ   C 

1ft 

Newark,  N.  J  

593  683 

I     2.18 
j     2.68 

New  Bedford,  Mass  

1  088 

(     2.35 

New  Haven,  Conn  

75  018 

j     3.80   ) 

g 

10 

New  Orleans,  La  

290  848 

\     3.36   j 
2  85 

T  Block 

Newport,  Ky.  .  .  

3  150 

T 

New  York,  N.  Y  

3  990  448 

5    a.»5  I 

Norfolk,  Va  

20,000 

\     2.72 
200 

Block 

Oakland,  Cal  

1,500 

Omaha,  Neb  

680  836 

j     2.17   ) 

T  A 

5 

Paterson,  N.  J  

26  400 

(     1.45  1 

Pawtucket,  R.  I  

2,576 

3  15 

a 

Peoria,  111  

160  233 

(     1.97   ) 

TT' 

Philadelphia,  Pa  

3,298,902 

j     1.85   C 
1     2.30   ) 

i  A 
TEAS 

Pittsburg,  Pa  

1  570  061 

(     2.05  [ 

Portland,  Oregon  

106  928 

Providence,  R.  I  

57  232 

0   f)K 

Re.iding,  Pa  

1  00  299 

Richmond,  Va  

6  400 

ASPHALTUM  AND   COAL-TAE   PAVEMENTS. 


171 


TABLE  XXXV.— Continued. 

EXTENT  AND   COST  OF  ASPHALT  PAVEMENT  IN  THE  PRINCIPAL  CITIES  OF 
THE  UNITED  STATES,  1898-99. 


Square 
Yards. 

Cost  of  Con- 
struction 
per  Sq.  Yd. 

Kind  of 
Asphalt. 

Guaranty 
Period. 
Years. 

Rochester  N  Y  

579  480 

(  $2.77   ) 

Ts  a 

Rockford,  111  

26  268 

\     2.33    j 
1  65 

T 

6  372 

Saginaw    Midi    •• 

54  7°6 

(     2.39   I 

TA 

St   Joseph  Mo    .    .               

143  064 

I     1-54  J 
2  15 

T 

St  Louis,  Mo    

232  108 

2  25 

TAR 

1  and  3 

St.  Paul,  Minn  

279  516 

j     2.46   { 

T  B 

10 

Salern    Muss        .             

3  042 

(     2.08  J 

Salt  Lake  City   Utah  

64  144 

2  74 

TT   P 

3  000  000  ± 

C   R 

140  813 

V-',    -1* 

Scranton   Pa  ••  

234  756 

5     2.47   ) 

Sioux  City,  Iowa  

68  570 

1     2.^6    f 
238 

T 

South  Bend,  Ind  

47,245 

Spokane   ^V^ash  

33  975 

4976 

5     2.50  ) 

T-R  T? 

10 

Springfield   Mo  

3,200 

(     3.07  J 

430,944 

(     2.00   } 

5  and  10 

Tacorna    W^ash  ............... 

58,000 

}     2.20.   i 
2.00 

r» 

Terre  Haute    lud  

66,000 

j     2.14  ) 

T 

5 

Toledo,  O  

316,204 

[     1.95  f 
j     2.50  1 

)      1  ory  i 

T  T' 

5 

Topeka  Kans 

194  000 

(     1-97  J 

T 

Trenton,  N.  J  

46,659 

Troy,  N.  Y  

105,600 

2.50 

T.  S 

Utica  N  Y  

503,236 

2.26 

TEA 

Washington   D   C       

3,027,788 

I     2.19   ) 

•<        -    ryn     r 

T  B 

2,600 

(     1.^8   f 

Wilkesbarre  Pa  

206,114 

Williamsport   Pa  .         

44,464 

\Vilroinffton    Del 

844 

Block 

9,124 

2.50 

Asphaltina 

5 

Yonkers  NY    

129,182 

2.89 

T 

60,336 

2.48 

T 

172 


HIGHWAY    CONSTRUCTION. 


TABLE   XXXV.— Continued. 
EXTENT  AND  COST  OF  ASPHALT  PAVEMENTS  IN  SOME  FOREIGN  CITIES. 


Square 
Yards. 

Cost  of  Con- 
struction 
per  Sq.  Yd. 

Kind  of 
Asphalt. 

Guaranty 
Period. 
Years. 

60,000 

j     3  60   ) 

s 

Toronto        "      

400,000 

1     3.10  C 

\    2.20  ) 

T 

10 

1,000,000 

(    1.80  J 
3.50 

ER 

London   Eufirluiid             •  

500  000 

j     4.50  ) 

E  R 

2  000  000 

\     3.75  f 

4  00 

ER 

T  =  Trinidad  Lake. 
T'=        "        Land. 
A  =  Alcatraz. 
B  =  Bermudez. 
C  =  California. 
G  =  German. 
K  =  Kentucky. 


M      =  Mexican. 

A  R  =  American  Rock. 

I  T    =  Indian  Territory. 

U      =  Utah. 

S       =  Sicilian. 

E  R  =  European  Rock. 


it  in  good  condition  for  a  fixed  number  of  years.  In  America  the 
cost  of  maintenance  is  included  in  the  price  paid  for  the  construc- 
tion, and  the  period  varies  from  five  to  fifteen  years. 

In  Europe  a  fixed  price  is  paid  for  construction,  and  the  com- 
pany  maintain  the  surface  free  for  two  years,  after  which  period 
they  are  paid  a  certain  amount  annually  per  square  yard,  depending 
upon  the  amount  of  the  traffic  over  the  pavement,  for  maintaining 
it  in  good  condition  (usually  fifteen  years) ;  in  case  of  any  disturb- 
ance of  the  pavement  by  a  corporation  or  by  a  private  citizen,  the 
company  replaces  the  pavement  at  the  expense  of  such  corporation 
or  citizen,  and  is  responsible  for  the  maintenance  thereafter. 

A  force  of  men  is  kept  constantly  at  work  making  repairs,  and 
any  defect,  however  slight,  is  repaired  immediately. 

It  is  not  considered  that  the  necessity  for  continual  repairs  is 
an  evidence  of  poor  workmanship  in  the  original  construction  or  of 
defective  materials  used,  but  rather  that  an  earnest  endeavor  is 
being  made  to  keep  the  pavement,  even  under  heavy  traffic,  at  all 
times  in  perfect  order.  This  prompt  and  constant  repairing 
explains  the  superior  condition  of  the  pavements  in  the  cities  of 
Europe. 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS. 


173 


234.  In  Table  XXXV#  is  given  the  cost  of  maintaining  asphalt 
pavements  per  square  yard  per  annum  in  several  American  cities 
and  London,  Paris,  and  Berlin. 

TABLE  XXXVa. 
COST  OF  MAINTAINING  ASPHALT  PAVEMENTS. 


Locality. 

Cost  per 
Square  Yard 
per  Annum. 

Remarks. 

Cents. 
4£  to  9 

10-year  contract 

Buffalo,  N.  Y.: 

.047 

With  railroad  tracks. 

.048 

Without  "           " 

Business         "     

.148 

With 

.112 

Without  "          " 

$1.05 

1898. 

.64 

Painting  gutters  

.02 

Per  lineal  foot. 

Cleaning  and  pouring  cracks 

.01 

.08 

i  <       i.         «  < 
10-  year  contract. 

1897. 

Highest  

.7620 

.0017 

.1297 

Washington    DC         

li  to  2 

Cincinnati  ...   

.075 

By  contract  for  the  second  5  years, 

London  : 
Val  de  Travers  

.24 

the  first  5  years  being  0. 
Average  of  15  years. 

.19 

(i         «   «       <« 

Societe  Francaise         .    .  . 

.22 

K        «  «       it 

.40 

Including  renewal  of  TV  part  of 

Berlin  

$1.50 

the  surface  every  year. 
For  20  years  by  contract. 

174  HIGHWAY   CONSTRUCTION. 

238.  Mr.  Elliot  C.  Clarke  gives  the  following  as  the  cost  per 
square  yard   per   annum   of  Val   de  Travers   compressed   asphalt 
under  an  annual  traffic  tonnage  of  100,000  tons  per  yard  of  width: 

Interest  on  original  cost 19.4  cents 

Maintenance  per  square  yard 7.2     ** 

Scavenging  per  square  yard 0.8     " 

Total 27.4  cents 

Nothing  is  charged  for  renewal,  as  the  annual  sum  for  mainte- 
nance provides  for  the  asphalt  in  perpetuity. 

239.  The  items  composing  the  cost  of  an  asphalt  pavement  are: 

Cost  per  sq.  yd. 

Removal  of  old  pavement  and  grading $0.10 

6"  concrete  foundation  (1:2:5) 48 

400  Ibs.  asphalt  cement $8.00 

200  Ibs.  stone-dust 20 

1  cubic  yard  sand. 1.25 

$9.45 

This  will  lay  13  yards  = 73 

Labor  mixing 04 

Hauling 10 

Labor  laying 06 

Superintendence 025 .225 


$1.535 
To  which  are  to  be  added  profits,  risks,  etc. 

240.  Foundation. — A  solid  unyielding  foundation  is  indispen- 
sable with  all  asphaltic  pavements,  because  asphalt  of  itself  has  no 
power  of  offering  resistance  to  traffic;  consequently,  if  the  founda- 
tion is  not  thoroughly  solid  and  unyielding  the  weight  of  the  traffic 
will  crush  it,  and  the  asphalt  will  give  way  in  all  directions  and  go 
to  pieces.  Two  classes  of  foundation  are  used :  (1)  Hydraulic- 
cement  concrete;  (2)  Bituminous  concrete. 

Recently,  with  the  object  of  reducing  the  cost  of  construction, 
the  asphaltic  paving  composition  has  been  laid  upon  the  surface  of 
old  macadam,  cobble,  and  stone-block  pavements,  and  the  results 
seem  to  be  equally  as  satisfactory  as  with  the  concrete  foundations. 

Old  brick  pavements  have  been  used  at  Youngstown,  Ohio,  as 
a  foundation  for  asphalt.  The  brick  pavement  is  thoroughly 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  175 

swept  and  washed  clean,  and,  after  it  is  dry,  it  is  heated  with  sur- 
face heaters,  which  destroys  all  combustible  matter  and  completely 
dries  the  brick.  While  they  are  still  warm  the  surface  of  the 
bricks  is  painted  with  a  thin  coat  of  asphalt  applied  with  brushes; 
If  the  holes  and  depressions  are  deep,  they  are  filled  with  broken 
stone  mixed  with  asphaltic  cement;  and  if  shallow,  they  are  filled 
with  the  same  material  as  the  surface  coat  and  thoroughly  tamped. 
On  this  the  surface  coat  is  placed  in  the  usual  manner. 

241.  Each  class  of  concrete  has  its  advantages  and  disadvan- 
tages: with  cement  concrete,  the  bond  between  the  foundation  and 
the  wearing  surface  is  not  very  great,  hence  it  is  very  easy  to  strip 
off  the  surface  in  case  repairs  are  necessary;  but,  on  the  other  hand, 
the  surface  sometimes  slips  on  the  foundation,  and  under  traffic 
rolls  into  waves  and  irregular  surfaces,  and  sometimes  cracks  with 
sudden  and  great  changes  of  temperature.     A   cement   concrete 
foundation  must  be  set  and  thoroughly  dry  before  the  asphalt  is 
laid;  the  best  asphalt  laid  in  the  most  skilful  manner  on  first-class 
but  damp  concrete  will  rapidly  go  to  pieces.     When  the  hot  asphalt 
is  applied  to  a  damp  surface  the  water  is  immediately  sucked  up 
and  turned  into  steam,  which  tries  to  escape  through  the  heated 
material;  the  result  is  that  coherence  is  prevented,  and,  although 
the  surface  of  the  asphalt  is  smooth,  the  mass  is  really  disintegrated 
from  underneath  by  its  bitter  enemy,  "water."     As  soon  as  the 
pavement  is  subjected  to  the  action  of  traffic,  the  fissures  formed  by 
the  steam  appear  on  the  surface,  and  the  whole  pavement  quickly 
falls  to  pieces.     For  the  same  reason  asphalt  should  be  laid  only  in 
dry  weather. 

242.  With  bituminous  concrete  the   foundation  and  wearing 
surface  are  united  into  one  mass  and  cannot  be  easily  separated. 
Repairs  are  difficult,  but  waving  and  cracking  are  less  frequent,  and 
the  bituminous  concrete  is  less  expensive. 

243.  Asphalt  Cement  Pavements  are  composed  of  two  essential 
parts,  the  matrix  and  the  aggregate,  and  the  success  or  failure  of 
the  pavement  will  depend  upon  the  care  exercised  in  selecting  the 
materials  and  the  skill  displayed  in  combining  them  and  laying  the 
pavement. 

244.  The  matrix  consists  of  cement  prepared  from  some  selected 
asphaltum   in   the  manner   described    in   Art.    96.      Its    proper- 


176  HIGHWAY    CONSTRUCTION. 

tion  varies  from  10  to  15  per  cent,  according  to  the  character  of 
the  aggregate,  climate  of  the  locality  where  used,  amount  and  char- 
acter of  the  traffic.  In  cold  climates  more  cement  is  required  than 
in  warm  ones;  pavements  subject  to  constant  and  heavy  traffic  re- 
quire less  cement  than  those  used  by  light  traffic. 

245.  The  aggregate  consists  of  sand  and  stone-dust. 

246.  In  quality  the  sand  should  be  equal  to  that  used  for  the 
best  quality  of  hydraulic  cement  mortar;  it  must  be  free  from  loam 
and  vegetable  impurities;  its  character  should  be  angular  grains 
ranging  from  coarse  to  fine.     (See  also  Art.  252.)     All  of  it  should 
pass  a  10-mesh  screen  ;  20  per  cent  an  80-mesh  screen;  and  10  per 
cent,  a  lOO-mesh  screen. 

247.  The   stone-dust  is  used  to  aid  in  filling  the  voids  in  the 
sand  and  thus  reduce  the  amount  of  cement  required  for  this  pur- 
pose (the  voids  in  sand  range  from  0.30  to  0.50  per  cent).     The 
amount  used  will  vary  with  the  coarseness  of  the  sand  and  quality 
of  the  cement.     The  proportion  used  ranges  from  5  to  15  per  cent. 
All  of  it  should  pass  through  a  30-mesh  screen,  and  75  per  cent 
should  pass  a  lOO-mesh  screen. 

248.  As  to  the  quality  of  the  stone-dust;  that  from  any  durable 
stone  is  equally  suitable.     Limestone-dust  was  originally  used  and 
lias  never  been  entirely  discarded,  although  it  may  be  one  of  the 
weak  elements  in  the  composition;   for  carbonate  of  lime,  though 
practically  insoluble  in   pure  water,  is  decidedly  soluble  in  water 
containing  carbonic  acid  gas.     As  rain-water  contains  this  gas  in 
absorption,  its  action  upon  the  lime  in  the  pavement  is  to  slowly 
dissolve  it,  and  thus  expose  the  cement  to  the  oxidizing  action  of 
the  atmosphere.     Organic  and  weak  acids   such  as  are  found  on 
streets  also  decompose  the  lime. 

249.  The  paving  composition  is  prepared  by  heating  the  mixed 
sand  and  stone-dust  and  the  asphalt  cement  separately  to  a  tem- 
perature of  about  300°  F.     The  heated  ingredients  are  measured 
into  a  pug-mill  and  thoroughly  incorporated;  when  this  is  accom- 
plished, the  mixture  is  ready  for  use.     It  is  hauled  to  the  street  in 
iron  carts,  the  interior  surface  of  which  is  previously  painted  with 
petroleum  oil  to  prevent  it  from  sticking;  it  is  spread  with  iron 
rakes  to  such  depth  as  will  give  the  required  thickness  when  com- 
pacted (the  finished  thickness  varies  from  1^  to  2|  inches  ;    the  re- 
duction of  thickness  by  compression  is  generally  about  40  per  cent). 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  177 


250.  The  compression  is  accomplished  by  means  of  rollers  and 
tamping-irons,  the  latter  being  heated  in  a  fire  contained  in  an  iron 
basket  mounted  on  wheels  ;  these  irons  are  used  for  tamping  such 
portions  as  are  inaccessible  to  the  roller,  viz.,  gutters  and  around 
manhole  heads,  etc.  Two  rollers  are  generally  employed — one  a 
hand-roller  weighing  about  800  pounds,  the  other  a  steam-roller 
of  the  form  shown  in  Chap.  XXIII,  ranging  in  weight  from 
5  to  10  tons.  The  surface  of  the  hand-roller  is  painted  with 
kerosene  to  prevent  the  mixture  from  sticking  to  it,  and  is 
generally  propelled  by  four  or  more  men  walking  on  the  surface 
of  the  heated  paving  mixture.  The  hand-roller  is  being  super- 
seded by  heating  the  front  roll  of  the  steam-roller;  the  heating  is 
effected  either  by  fire  carried  in  an  iron  basket  suspended  from  the 
axle  inside  the  roller,  or  by  an  attachment  for  using  steam  from  the 
boiler.  Two  steam-rollers  are  sometimes  employed,  one  weighing 
from  5  to  6  tons  and  of  narrow  tread— this  is  used  to  give  the  first  com- 
pression; and  the  other,  weighing  about  10  tons  and  of  broad  tread, 
is  used  for  finishing.  The  amount  of  rolling  varies;  the  average  ap- 
pears to  bo  about  one  hour  per  one  thousand  square  yards  of  pave- 
ment. After  the  primary  compression  by  either  the  hand  or 
heated  roller  natural  hydraulic  cement  or  any  impalpable  mineral 
matter  is  sprinkled  over  the  surface  to  prevent  the  adhesion  of  the 
material  to  the  cold  roller  and  to  give  the  surface  a  more  pleasing 
color.  To  prevent  rotting  of  the  paving  material  in  the  gutters 
they  are  formed  of  either  hydraulic  cement,  granite  blocks,  vitri- 
1  fied  brick,  etc.,  or  when  the  asphaltic  material  is  laid  up  to  the 
curb  the  surface  of  the  portion  forming  the  gutter  is  painted  with 
a  coat  of  hot  asphaltic  cement. 

251.  The  paving  composition  is  usually  spread  upon  the  foun- 
dation in  two  layers;  the  first  is  called  the  "binder"  or  "cushion 
<x>at";  it  contains  from  2  to  5  per  cent  more  cement  than  the  sur- 
face layer;  its  finished  thickness  varies  from  one  half  to  one  and  one- 
lialf  inches.  The  object  of  the  binder  is  to  unite  the  surface  mixture 
with  the  foundation,  which  it  does  through  the  larger  percentage 
of  cement  that  it  contains,  and  which  if  put  in  the  surface  mixture 
would  render  it  too  soft.  When  the  "  binder  "  has  been  compressed, 
it  is  ready  to  receive  the  surface  coat,  which  is  laid  and  compressed 
as  above  described.  When  bituminous  concrete  is  used  as  the  foun- 
dation, the  "  binder"  is  omitted.'  When  the  pavement  is  to  be  laid 


178  HIGHWAY    CONSTRUCTION. 

upon  the  surface  of  an  old  pavement,  the  binder  or  cushion  coat  i.; 
used  to  fill  up  the  inequalities  and  bring  its  surface  to  the  uniform 
grade  and  contour. 

252.  Failure  of  Asphaltic  Cement  Pavements. — The  failure  of 
this  class  of  pavement  may  be  attributed  to  any  one  or  all  of  the 
following  causes: 

(1)  Unsuitable  asphaltum.     (That  is,  asphaltum  which  has  been 
so  changed  by  natural  causes  as  to  possess  little  or  no  cementing^ 
power.) 

(2)  Too  high  temperature  in  refining  the  crude  asphaltum.  (That 
is,  a  temperature  which  converts  the  petroleue  or  cementing  me- 
dium of  the  asphaltum  into  asphaltene  and  thus  reduces  or  entirely 
destroys  its  cementing  qualities.) 

(3)  Too  loiu  a  temperature  continued  for  a  considerable  length  of 
time.     (This  has  the  same  effect  as  a  high  temperature  for  a  short 
time,  and  is  analogous  to  the  action  of  solar  heat,  which  through- 
ages  has  been  changing  the  liquid  bitumen  wherever  exposed  into, 
asphaltum.) 

(4)  Unsuitable  fluxing  agents,     (Such'  as  those  which  are  not 
solvents  of  the  asphaltene  and  thus  form  a  mechanical  instead  of  a 
chemical  union,  or  fluxes  which,  contain  volatile  oils,  which  under 
the  action  of  solar  heat  evaporate  from  the  pavement  and  leave  it 
porous  and   in  a  condition    to   absorb   rain-water,   the   oxidizing 
action  of  which  is  to  gradually  convert  the  petrolene  or  cementing 
agent  of  the  bitumen  into  asphaltene,  thus  rendering,  the  pavement, 
brittle,  in  which  condition  it  is  easily  broken  up  under  the  action  of 
the  traffic.) 

(5)  Unsuitable  temperature  employed  during  the  process  of  flux- 
ing.    (That  is,  either  a  high  temperature  for  a  short  time  or  a  low 
one  for  a  long  time,  the  effects  of  which  are  similar  to  those  stated 
under  2  and  3.) 

(6)  Unsuitable  sand.    (That  is,  sand  either  too  coarse  or  too  fine,, 
or  a  sand  of  suitable  fineness,  but  containing  loam,  vegetable  matter 
or  clay.    The  sand  should  be  clean,  sharp,  large-grained,  and  not  too- 
uniform  in  size,  well  screened  and  if  necessary  washed.  The  presence 
of  clay  prevents  that  intimate  contact  between  the  cement  and  the 
grains  of  sand   so  essential  to  a  homogeneous   body,  because  the 
particles  of  clay  adhere  to  the  grains  of  sand  and  form  diaphragms 
between  it  and  the  cement.     The  sand  imparts  crushing  strength 


ASPHALTUM    AND    COAL-TAR   PAVEMENTS.  179 


and  fulfils  practically  the  same  offices' as  in  hydraulic  cement  mor- 
tar, therefore  its  quality  should  be  in  all  respects  equal  to  that 
used  in  the  best  mortar  for  important  structures.) 

(7)  Use  of  limestone-dust.     (This  material  is  speedily  dissolved 
by  rain-water  and  some  of  the  organic  acids  found  in  streets;  its 
dissolution  leaves  the  pavement  in  the  same  condition  and  exposed 
to  the  same  agent  of  destruction  as  described  under  cause  4.)* 

(8)  Insufficient  mixing  of  the  ingredients.     (Whereby  the  ce- 
ment and  the  particles  of  sand  are  not  brought   into   intimate 
contact ;  to  secure  a  strong  mortar  or  concrete  it  is  essential  that 
each  piece  of  the  aggregate  shall  be  entirely  surrounded  by  the 
cementing  material,  so  that  no  two  pieces  are  in  actual  contact.) 

(9)  Insufficient  quantity  of  cement.     (The  quantity  of  cement 
required  to  coat  each  particle  of  the  sand  will  vary  with  the  char- 
acter of  the  sand;  if  the  grains  in  a  given  volume  are  small,  the 
magnitude  of  the  total  surface  to  be  covered  is  greater  than  when 
the  grains  are  large;  hence  a  fine  sand  requires  more  cement  than  a 
coarse  one;  therefore  the  proportion  of  the  cement  must  be  varied 
to  suit  the  character  of  the  sand  to  be  used,  or  else  the  quality  of 
the  pavement  will  be  impaired.) 

(10)  Laying    the    paving   composition    on   a   wet  foundation. 
(When  hydraulic  concrete  is  used  as  the  foundation,  it  must  be  set 
and  thoroughly  dry  before  the  asphalt  is  laid  upon  it;  if  not,  the 
contained  water  will  be  sucked  up  and  converted  into  steam,  which 
tries  to  escape  through  the  heated  material ;  the  result  is  that  co- 
herence of  the  asphaltic  mixture  is  prevented,  and,  although  its 
surface  may  be  smooth,  the  mass  is  really  honeycombed,  and  as  soon 
as  the  pavement  is  subjected  to  the  action  of  traffic  t-he  voids  or 
fissures  formed  by  the  steam  appear  on  the  surface,  and  the  whole 
pavement  is  quickly  broken  up.)  f 

*  The  results  obtained  from  several  experiments  indicate  that  the  presence 
of  finely  divided  amorphous  calcium  carbonate,  calcium  oxide,  silicic  oxide, 
or  free  or  fixed  carbon  is  detrimental  to  nsphaltum.  The  action  of  these  sub^ 
stances  is  to  take  up  the  oily  constituent  and  pass  it  from  one  particle  to 
another  until  the  surface  of  the  mass  is  reached,  where  it  is  expelled  in  such  a 
metamorphosed  condition  that  the  oil  is  changed  from  a  partial  non-volatile 
to  a  slowly  or  even  a  rapidly  volatile  state  at  ordinary  temperatures,  and  in 
some  cases  a  portion  at  least  in  gaseous  form.  The  effect  of  this  action  is  to 
produce  a  porous  mass  easily  disintegrated. 

f  The  length  of  time  which  should  elapse  before  the  asphalt  is  laid  upon 


180  HIGHWAY    COXSTRUCTTOX. 

(11)  Weak  or  insufficient  foundation.     (A  weak  or  improperly 
prepared  foundation  will,  by  unequal  settlement  and  settlement  in 
spots,  cause  cracks  and  depressions  in  the  asphalt  surface  which 
under  traffic  will  be  speedily  enlarged,  and  the  pavement  will  there- 
fore be  broken  up.) 

(12)  Use   of  paving  mixture  which  has  become  chilled.     (Al- 
though asphaltum  is  a  bad  conductor  of  heat,  and  the  cement  re- 
tains its  plasticity  for  several   hours,  occasions  may  and  do  arise 
through  which  the  composition  before  it  is  spread  or  rolled  has 
cooled;  its  condition  when  this  happens  is  analogous  to  hydraulic 
cement  which  has  taken  a  "set,"  and  the  same  rules  which  apply 
to  hydraulic  cement  in  this  condition  should  be  respected  in  regard 
to  asphaltic  cement.) 

(13)  Insufficient  compression.     (To  prevent  the  admission  of  the 
rain  and  other  water  falling  upon  the  surface  of  the  pavement,  and 
its  destroying  effects,  it  is  necessary  that  the  paving  composition  be 
compacted  into  a  solid  homogeneous  mass;  if  not,  the  oxygen  con- 
tained in  the  water  will  have  the  effect  described  under  cause  4.) 

(14)  Lack  of  water-tight  connection  with  street  furniture,  curbs, 
and  crossings,  which  permits  the  entrance  of  water  under  the  as- 
phaltic surface. 

(15)  Destruction  by  natural  causes.  (All  materials  in  nature  are 
undergoing  changes  due  to  the  action  of  the  elements,  and  asphal- 
tum is  no  exception.  Under  the  action  of  solar  heat  and  water  all 
the  bitumens  undergo  a  change ;  this  change  is  due  to  evaporation, 
volatilization,  and  oxidation,  and  tends  at  first  to  greater  solidifi- 
cation or  hardness.  When  the  maximum  degree  of  hardness  is  at- 
tained, natural  decay  apparently  commences,  and  under  the  com- 
bined action  of  organic  acids,  rain-water,  and  frost  the  material 
seems,  so  to  speak,  to  rot  and  finally  disintegrate.  At  any  stage  of 
the  change  the  substance  is  still  asphaltum  and  the  process  is 
termed  "ageing,"  and  a  great  deal  of  the  controversy  regarding 
the  relative  qualities  of  different  asphaltums  is  due  to  ignoring  the 
changes  wrought  by  nature.  While  these  changes  are  slow  in 

the  concrete  depends  upon  two  conditions  ;  the  character  of  the  cement  and 
atmospheric  conditions.  It  is  desirable  that  ten  days  at  least  should  elapse 
before  surfacing,  accompanied  in  warm  weather  by  frequent  sprinkling.  There 
is  no  objection  to  lay  surface  in  cold  weather  if  proper  attention  is  paid  to  the 
temperature  of  the  mixture. 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  181 

nature,  some  or  all  of  them  may  be  hastened  by  the  unskilful 
application  of  artificial  heat  in  preparing  the  material,  and  by  the 
action  of  the  organic  acids  and  rain-water  falling  upon  the  pave- 
ment. 

The  failure  or  disintegration  of  an  asphalt  pavement  manifests 
itself  in  different  ways  according  to  the  cause  and  character  of  the 
pavement. 

Disintegration  caused  by  water  entering  the  pavement  either 
from  the  surface  or  through  the  base  manifests  itself  differently, 
depending  upon  the  character  of  the  pavement.  If  the  asphalt  sur- 
face is  soft,  or  the  surface  of  the  concrete  smooth,  the  first  defect 
noticed  will  be  the  tendency  of  the  pavement  to  become  wavy  in 
warm  weather.  This  is  due  to  the  under  portion  of  the  surface 
mixture  rotting,  so  to  speak,  thus  destroying  the  cementing 
properties  of  the  asphalt.  The  upper  portion,  although  good, 
being  deprived  of  the  support  of  the  affected  mixture  under 
it,  will  be  crowded  out  by  the  traffic.  This  crowding  is  assisted  by 
the  surface  of  the  base  being  smooth,  and  also  by  the  bond  between 
the  base  and  binder  being  destroyed  by  the  moisture. 

In  cases  where  the  surface  of  the  base  is  rough  and  the  surface 
mixture  hard  the  principal  disintegration  will  take  place  in  cold 
weather,  nothing  abnormal  being  noticed  until  the  pavement  begins 
a  rapid  crumbling  away  in  the  affected  spot  under  traffic. 

On  examining  a  section  of  asphalt  surface  disintegrating  from 
t'his  cause,  especially  where  it  has  not  been  going  on  for  too  long  a 
time,  there  will  be  found  a  layer  of  perfectly  sound  and  good 
material  at  the  surface  of  the  pavement,  while  underneath  the  mix- 
ture will  show  evidence  of  being  disintegrated  by  water;  that  is, 
the  sand  will  appear  clean  and  white  in  spots,  as  though  there  had 
been  a  deficiency  of  asphalt  cement  to  cover  it.  The  base  under 
the  affected  pavement  will  generally  be  found  damp  or  even  wet. 
In  Washington,  D.  C.,  the  destruction  of  several  pavements  from 
this  cause  has  been  prevented  by  the  use  of  blind  drains  put  in 
under  the  gutter  next  to  the  lawn  or  terrace,  and  in  some  cases 
having  bone  drains  placed  under  the  pavement. 

Disintegration  caused  by  unsuitable  oils  or  coal-tar  in  the 
binder  is  manifested  by  a  slight  depression  over  the  affected  spots. 
In  time  numbers  of  small  cracks  appear,  running  parallel  with  the 


182  HIGHWAY    CONSTRUCTION. 

street;  these  gradually  increase  in  importance,  accompanied  with 
transverse  cracks,  until  the  pavement  has  the  appearance  of  an  alli- 
gator-skin. On  examining  a  section  of  the  surface  mixture  cut 
from  the  affected  spot  it  will  be  found  to  be  quite  soft  near  the 
binder,  if  the  disintegration  has  not  proceeded  for  a  length  of  time; 
if  older,  the  soft  zone  will  be  nearer  the  surface,  while  the  bottom 
of  the  mixture  will  show  the  disintegrating  effect  of  the  water  that 
has  likely  entered  the  pavement  through  the  crack.  The  affected 
piece  of  mixture  will  smell  strongly  of  coal-tar  (if  coal-tar  was  used 
in  the  binder),  and  will,  in  all  cases,  give  a  greenish  fluorescence  to 
a  solution  in  carbon  disulphide.  The  portion  of  the  pavement  thus 
acted  on  will  be  crowded  or  worn  out  by  the  traffic  until  nothing  is 
left  of  it.  If  the  surface  mixture  is  soft,  the  pavement  will  roll  at 
this  place,  the  soft  affected  material  crowding  before  the  traffic. 
Binder  made  with  asphalt  cement,  in  some  few  cases,  affects  the 
surface  mixture  in  the  same  way,  due  probably  to  the  presence  of 
some  free  oil,  which  may  not  have  been  properly  incorporated  with 
the  asphalt  in  making  the  binder  cement. 

Disintegration  caused  by  the  absorption  of  illuminating-gas  be- 
comes apparent  in  very  much  the  same  way  as  when  coal-tar  is  the 
cause,  except  that  the  fine  cracks,  running  parallel  with  the  street, 
make  their  appearance  some  time  before  the  pavement  begins  to 
roll.  Pieces  of  the  surface  mixture  taken  up  smell  very  strongly  of 
illuminating-gas,  and  in  some  cases  the  gas  can  be  ignited  by  apply- 
ing a  match  to  the  under  surf  ace  when  it  has  just  been  taken  up.  In 
nearly  every  case  enough  gas  will  be  given  off  by  heating  a  small 
piece  of  the  affected  pavement  in  a  tube  to  have  it  flash  by  ignit- 
ing. (See  Art.  226.) 

Disintegration  caused  by  a  deficiency  of  asphalt  cement  will  be 
made  apparent  by  cracking  and  crumbling  during  cold  weather. 

Defective  bond  between  base  and  binder,  or  between  binder  and 
•wearing  surface,  is  shown  by  rolls  and  waves.  (See  also  Art.  303#.) 

253.  Trinidad  Asphalt  Pavements. — The  source  of  the  asphal- 
tum  used  in  this  class  of  pavement  is  described  in  Art.  100.  The 
characteristics  of  the  crude  asphaltum  are  given  in  Art.  100^7. 

The  method  of  refining  is  described  in  Art.  lOOe. 

The  characteristics  of  the  refined  asphaltum  are  given  in  Art. 


ASPHALTUM    AND    COAL-TAR   PAVEMENTS. 


183 


,  and  the  relative  qualities  of  "Like"  and  "land"  asphaltuni 
are  discussed  in  Art.  WOp. 

The  paving  material  consists  of  silicious  sand  and  stone-dust 
{usually  limestone)  cemented  together  with  asphaltic  cement,  man- 
ufactured as  described  in  Art.  96.  The  proportions  of  the  ingre- 
dients are  not  constant,  but  vary  with  the  climate  of  the  place 
where  the  pavement  is  to  be  used,  the  character  of  the  sand, 
«nd  the  amount  and  character  of  the  traffic  that  will  use  the  pave- 
ment; the  range  in  the  proportions  is  as  follows  : 

Asphalt  cement 12  to  15  per  cent. 

Sand 83to70    "      " 

Stone-dust 5  to  15    "      " 

100—100 

The  sand  and  asphaltic  cement  are  heated  separately  to  about 
300°  F.  The  stone-dust  (pulverized  carbonate  of  lime)  is  added  to 
the  hot  sand  in  the  required  proportions,  and  is  then  mixed  with 
the  hot  asphaltic  cement  in  a  suitable  mixing  machine  and  thor- 
oughly incorporated;  when  this  is  accomplished,  the  mixture  is 
ready  to  be  laid  on  the  street. 

Specifications  for  Trinidad  asphalt  pavements  are  given  in  Ar- 
ticles 262,  263,  and  264. 

254.  The  proportions  of  the  materials  for  the  Trinidad  asphalt 
pavements  at  Washington,  D.  0.,  average  as  follows: 


Cranford. 

Barber. 

Weight  of— 

Pounds. 

Per  cent. 

Pounds. 

Per  cent. 

Sand                   

584 
54 
80 
111 

75.0 
6.9 
3.8 
14.3 

637 
60 
35 
125 

74.3 

7.0 
4.1 
14.6 

•Stone  dust  

COMPOSITION    OF    PAVING    MIXTURES. 

255.  The  following  table  shows  the  maximum,  minimum,  and 
average  per  cent  of  the  bitumen,  and  the  mesh  composition  of.  the 
•sand,  in  the  paving  mixtures  used  at  Washington,  D.  0.,  during 
1899: 


184  HIGHWAY   CONSTRUCTION. 

Eastern  Crariford 

Bennudez        Paving  Co. 
Paving  Co. 

Number  of  samples 29  62 

Average  per  cent  bitumen 10.7  10.7 

Lowest      "      "          " 9.1  9.3 

Highest     "      "           "        12.0  12.3 

Sand — Per  cent  retained  on  sieve  having 

20  rnesli  per  inch 2.5  3.0 

40     "       "      " 20.0  25.5 

60     "       "      "    31.9  38.3 

80     "       "      "    8.3  7.0 

100     "       "      "    10.8  6.5 

Passed  100  mesh 26.0  18.5 

256.  Memoranda. — One  ton  of  refined  asphaltum  mixed  with 
the  flux  makes  about  2300  pounds  of  asphaltic  cement,  equal  to 
about  3.4  cubic  yards  of  paving  material. 

One  cubic  yard  of  paving  mixture  contains  one  cubic  yard  of 
sand,  675  Ibs.  ±  of  asphaltic  cement,  and  490  Ibs.  ±  stone-dust; 
weighs  about  4500  Ibs.,  depending  upon  the  character  of  the  sand; 
and  will  lay  the  following  amount  of  surface: 

2£  inches  thick 12  square  yards 

2        "         "     18      " 

H      "         "     27      " 

257.  Temperatures. 

Refining,  not  over 400°  F. 

Fluxing,  "  "  325°F. 

Sand— Lowest 250°  F. 

Highest         300°  F. 

In  cold  weather  not  lower  than 280°  F. 

Mixing  ingredients 275°  F. 

When  spreading not  lower  than  250°  in  summer  or  275°  F. 

in  winter.  Never  over 300°  F. 

Cold  or  chilled  mixture  should  not  be  used.  No  compaction 
can  be  secured  with  such  material. 

It  is  doubtful  if  surface  mixture  can  be  successfully  reheated. 

258.  Extracts    from    the   Reports   of   City   Civil  Engineers. — 
Washington,  D.  C.   (Capt.   Greene,  1885).— The  Trinidad  asphalt 
has  been  the  standard  pavement  for  the  last  seven  years,  about 
600,000  square  yards  having  been  laid  on  a  foundation  of  hydraulic 
concrete,  and  about  160,000  yards  more  on  the  stone  foundations  of 
the  worn-out  tar  pavements.      Its  cost  for  the  last  three  years 
has  been  about  $2.25  per  square  yard.     When  made  with  skilled 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  185 

labor  and  laid  under  proper  supervision  it  seems  to  answer  all  tho 
requirements  of  a  first-class  pavement  in  this  city.  It  is  almost 
noiseless,  not  slippery,  under  ordinary  conditions  offers  little  resist- 
ance to  traction,  is  easily  repaired  and  cleaned,  and  is  very  dur- 
able. Large  numbers  of  streets  have  been  laid  five,  six,  and  seven 
years,  and  are  in  perfect  order,  although  not  a  cent  has  been  ex- 
pended on  them  for  repairs.  On  other  streets  mistakes  have 
occasionally  been  made  in  the  mixture,  and  defects  have  appeared 
which  needed  repairs.  Nearly  all  these  repairs  have  been  made  at 
the  contractor's  expense  during  his  guarantee  period;  but  as  nearly 
as  it  can  be  ascertained  the  total  expense  both  to  contractors  and 
the  District  for  repairing  asphalt  pavements  during  the  eight  years 
since  they  were  first  laid  has  been  about  $30,000,  or  $3750  per  year, 
so  that  the  average  annual  expense  for  maintenance  up  to  date  has 
been  -fa  of  one  cent  per  yard  per  year.  This  is  certainly  a  small 
expense  for  the  luxury  of  smooth  pavements,  and  much  less  than 
for  any  other  pavement  having  the  combined  durability  and  smooth- 
ness of  the  asphalt. 

259.  The  French  Asphalt  Pavement,  made  from  the  natural 
bituminous  limestone  of  Switzerland,  and  similar  in  every  respect 
to  the  asphalt  pavements  as  laid  in  Paris,  was  tried  here  in  1873 
and  1876,  31,388  yards  having  been  laid  on  the  following  streets, 
viz. :  Pennsylvania  Avenue,  between  First  and  Sixth  streets;  I  Street, 
betwen  Thirteenth  and  Fifteenth  streets;  and  Grant  Place,  between 
Ninth  and  Tenth  streets.     Experience  has  shown  that  this  pavement 
is  more  slippery  than  the  pavement  of  sand  and  Trinidad  asphalt, 
and  that  it  is  not  quite  as  durable.     Its  cost  is  nearly  fifty  per  cent 
greater;  for  these  reasons  no  more  of  it  has  been  laid. 

260.  Buffalo,  N.  Y.— The  streets  paved  with  asphalt  have  stood 
the  extreme  changes  of  this  climate  without  any  serious  defect, 
are  giving  satisfaction  to  our  people,  being  healthful,  easily  kept 
clean,  smooth,  yet  not  slippery. 

261.  Omaha,  Neb.—"  Our  temperature  varies  as  much  as  150 
degrees  Fahr.,  between  the  extremes  of  summer  and  winter.  We  are 
subject  to  rapid  changes  of  temperature,  which  in  the  winter  season 
occasionally  are  as  high  as  60  degrees  in  twenty-four  hours.     Doug- 
lass Street,  which  was  paved  in  the  fall  of  1882  and  spring  of  1883, 
has  experienced  a  range  of  temperature  of  from  120  degrees  in  the 
summer  to  34  degrees  below  zero  in  the  winter Our  experience 


186  HIGHWAY   CONSTRUCTION. 

is  very  favorable  to  asphalt  pavements  on  all  grades  ranging  from 
6  inches  to  4  feet  rise  per  100  feet,  and  I  am  not  sure  but  that  as 
high  as  5  or  6  feet  per  100  feet  may  be  favorably  overcome.  The 
asphalt  pavement  is  not  as  cheap  as  wood,  but,  in  my  opinion,  a 
preferable  pavement  upon  permanently  established  and  well-im- 
proved streets.  It  is  not  quite  as  easy  for  horses  as  wood,  but  more 
comfortable  for  those  who  ride,  is  more  cleanly,  and  from  a  sanitary 
standpoint  far  superior." 

262.  Heads  of  Specifications  for  Standard  Trinidad  Asphaltum 
Pavements. 

(1)  Preparation  of  Roadbed. 

(2)  Foundation.     (Hydraulic-cement  or  bituminous  concrete.) 

(3)  The  Wearing  Surface  will  be  composed  of 

(a)  Refined  Trinidad  asphaltum. 

(b)  Heavy  petroleum  oil. 

(c)  Find  sand  containing  not  more  than  one  per  centum 

of  hydrosilicate  of  alumina. 

(d)  Fine  stone-dust. 

(e)  Fine  powder  of  carbonate  of  lime. 

(4)  Preparation  of  the  Asphalt. — The  Trinidad  asphaltum  shall 
be  refined,  and  as  far  as  possible  freed  from  foreign  organic  and 
animal  matter  and  volatile  oil,  and  brought  to  uniform  standard  of 
purity  and  gravity,  containing  not  less  than  60  per  cent  of  bitumi- 
nous matter  soluble  in  bisulphide  of  carbon.     The  asphaltum  must 
be  refined  under  the  direction  and  to  the  satisfaction  of  the  engineer, 
and  kettles  will  not  be  drawn  lower  than  may  be  ordered  by  him. 

The  heavy  petroleum  oil  shall  be  freed  from  all  impurities  and 
brought  to  a  specific  gravity  of  from  18  to  22  degrees  Beaume  and 
a  fire  test  of  250  degrees  Fahrenheit. 

From  these  two  hydro  carbons  shall  be  manufactured  an 
asphalt  cement  which  shall  have  a  fire  test  of  250  degrees  Fahr., 
and  at  a  temperature  of  60  degrees  Fahr.  shall  have  a  specific 
gravity  of  1.19,  said  cement  to  be  composed  of  100  parts  of  pure 
asphalt  and  from  15  to  20  parts  of  heavy  petroleum  oil. 

(5)  Manufacture  of  the  Paving  Material. — The  asphalt  being 
prepared  in  the  manner  above  described,  the  pavement  mixture 
will  be  formed  of  the  following  materials,  and  in  the  proportions 
stated. 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  18' 

Asphaltic  cement from  12  to  15 

Sand «    83  "  70 

Pulverized  carbonate  of  lime ««      5   «  15 


or 


Asphaltic  cement from  13  to  16 

Saud •«    63   ••'   58 

Stone-dust •«    28   "  23 

Pulverized  carbonate  of  lime ««      3   "     5 

The  proportion  of  the  materials  will  depend  upon  their  char- 
acter and  the  traffic  on  the  street,  and  will  be  determined  by  the 
engineer.  If  the  proportions  of  the  mixture  are  varied  in  any 
manner  from  those  directed  to  be  used,  the  mixture  will  be  con- 
demned ;  and  if  already  placed  on  the  street,  it  will  be  removed  and 
replaced  by  proper  material,  at  the  expense  of  the  contractor. 

The  sand,  stone-dust  and  asphaltic  cement  are  to  be  heated  sep- 
arately to  about  300  degrees  Fahr.  The  pulverized  carbonate  of 
lime  while  cold  shall  be  mixed  with  the  hot  sand  and  stone-dust  in 
the  required  proportions,  and  then  mixed  with  the  asphaltic  cement 
at  the  required  temperature,  and  in  the  proper  proportion,  in  a 
suitable  apparatus,  which  will  effect  a  perfect  mixture.  The  pro- 
portions will  be  gauged  daily  in  the  presence  of  the  inspectors. 

(6)  Quality  of  the  Materials. — All  the  materials  used,  as  well  as 
the  plant  and  method  of  manufacture,  will  be  subject  to  the  inspec- 
tion and  approval  of  the  engineer.    The  degree  of  fineness,  both  of 
the  sand,  stone-dust,  and  powdered  limestone,  will  be  determined 
by  testing  with  screens,  as  follows:   The  powdered  carbonate  of 
lime  will  be  of  such  degree  of  fineness  that  15  per  cent  by  weight 
shall  be  an  impalpable  powder  of  limestone,  and  the  whole  of  it 
shall  pass  a  No.  26  screen.     The  sand  will  be  of  such  size  that 
more  than  50  per  cent  of  it  will  pass  a  No.  80  screen,  and  the 
whole  of  it  shall  pass  a  No.  20  screen.     The  stone-dust  shall  be  the 
residue  of  granite  or  other  approved  stone,  and  shall  pass  a  sieve  of 
not  more  than  6  meshes  to  the  inch. 

(7)  Laying  the  Asphalt.     (Two-coat  Pavements.)— The  pave- 
ment mixture,  prepared  in  the  manner  thus  indicated,  shall  be  laid 
on  the  foundation  in  two  coats.    The  first  coat,  called  cushion-coat, 
shall  contain  from  2  to  4  per  cent  more  asphaltic  cement  than 
given  above;  it  will  be  laid  to  such  depth  as  will  give  a  thickness 
of  J  inch  after  being  consolidated  by  a  roller.     The  second  coat, 


188  HIGHWAY   CONSTRUCTION. 

called  surface-coat,  prepared  as  above  specified,  shall  be  laid  on  the 
cushion-coat;  it  shall  be  brought  to  the  ground  in  carts  at  a  tem- 
perature of  about  250  degrees  Fahr.,  and  if  the  temperature  of  the- 
air  is  less  than  50  degrees  iron  carts  with  heating  apparatus  shall 
be  used  in  order  to  maintain  the  proper  temperature  of  the  mix- 
ture; it  shall  then  be  carefully  spread  by  means  of  hot  iron  rakes, 
in  such  manner  as  to  give  a  uniform  and  regular  grade,  and  to 
such  depth  that  after  having  received  its  ultimate  compression  it 
will  have  a  thickness  of  2  inches.  The  surface  then  shall  be  com- 
pressed by  hand  rollers,  after  which  a  small  amount  of  hydraulic 
cement  shall  be  swept  over  it,  and  it  then  shall  be  thoroughly  com- 
pressed by  a  steam  roller  weighing  not  less  than  250  pounds  to  the 
inch  run;  the  rolling  to  be  continued  for  not  less  than  five  hours, 
for  every  1000  yards  of  surface. 

(8)  Laying  the  Asphalt.    (One-coat  Pavement.) — The  pavement 
mixture,  prepared  in  a  manner  thus  indicated,  will  be  laid  on  tha 
foundation;  it  will  be  laid  to  such  depth  as  will  give  a  thickness  of 
2-|-  inches  after  being  consolidated  by  rollers.     It  will  be  brought 
to  the  ground  in  carts,  at  a  temperature  of  not  less  than  250  de- 
grees Fahr.  nor  more  than  310  degrees  Fahr.,  and  if  the  tempera- 
ture of  the  air  is  less  than  50  degrees  the  contractor  must  provide 
canvas  covers  for  use  in  transit.     It  will  then  be  carefully  spread 
by  means  of  hot  iron  rakes,  in  such  manner  as -to  give  uniform  and 
regular  grade  and  to  such  depth  that,  after  having  received  its. 
ultimate  compression  of  two  fifths,  it  will  have  a  net  thickness  of 
2J-  inches.      This   depth  will   be  constantly  tested  by  means  of 
gauges  furnished  by  the  engineer.     The  surface  will  then  be  com- 
pressed by  hand  rollers,  after  which  a  small  amount  of  hydraulic 
cement  will  be  swept  over  it,  and  it  will  then  be  compressed  by  a 
steam  roller  weighing  not  less  than  5  tons,  to  be  followed  by  another 
steam  roller  weighing  not  less  than  10  tons,  the  rolling  being  con- 
tinued for  not  less  than  10  hours  for  every  1000  yards  of  surface. 

(9)  In  order  to  make  the  gutters  entirely  impervious  to  water,. 
a  width  of  12  inches  next  the  curb  will  be  coated  with  hot  pure 
asphalt  and  smoothed  with  hot  smoothing-irons  in  order  to  saturate 
the  pavement  to  a  certain  depth  with  an  excess  of  asphalt;  or  if  so- 
directed  by  the  engineer,  the  gutters  will  be  formed  with  gutter- 
stones,  granite  blocks,  or  bricks,  in  accordance  with  the  specifica- 
tions for  such  work. 


ASPHALTUM    AND    COAL-TAR    PAYEMEXTS.  189 

(10)  Laying  Granite  Blocks  adjoining  Railway  Tracks. — 
When  asphalt  pavement  is  laid  in  a  street  containing  the  tracks  of 
•a  street  railrcad  one  row  of  selected  granite  paving-blocks  will  be 
laid  next  to  the  track,  alternating  as  headers  and  stretchers  tooth- 
ing into  the  pavement.  The  foundation  will  extend  to  the  depth 
of  the  bottom  of  the  cross-ties,  and  will  be  similar  in  all  respects  to 
the  foundation  of  the  carriageway  pavement,  except  as  to  the 
thickness  of  the  base.  If  the  foundation  consists  of  bituminous 
concrete,  the  blocks  will  be  laid  directly  upon  and  embedded  in  the 
binder  while  it  is  still  in  a  hot  and  plastic  condition.  If  the  foun- 
dation consists  of  hydraulic-cement  concrete,  the  base  will  be  cov- 
ered with  a  layer  of  fine  sharp  sand,  washed  and  dried,  2  inches  in 
thickness,  and  the  blocks  will  be  laid  directly  upon  and  embedded 
in  the  sand  with  close  joints. 

The  top  of  the  blocks  will  be  even  with  the  surface  of  the  tread 
of  the  rail,  which  shall  conform  with  the  grade  of  the  street.  The 
blocks  will  be  laid  before  the  asphaltic  wearing  surface  is  laid  upon 
the  carriageway,  and  carefully  rammed  to  a  firm  bed.  Care  will 
~be  taken  to  fit  them  well  up  against  the  stringers  or  web  of  the  rail 
of  the  railroad.  The  space  back  of  the  blocks  will  be  filled  to  the 
surface  of  the  base  for  the  carriageway  pavement  with  the  same 
material  as  is  used  for  said  base,  well  rammed. 

Immediately  after  the  wearing  surface  shall  have  been  laid, 
clean,  fine,  hot  gravel,  not  larger  than  one-half  inch  in  any 
direction,  will  be  poured  into  the  joints  of  the  blocks  until  they 
become  nearly  filled.  There  will  then  be  poured  into  the  joints,  at 
a  temperature  of  300  degrees  Fahr.,  paving  cement  made  of  No.  6 
coal-tar  distillate,  until  the  joints  are  completely  filled  flush  with 
the  surface  of  the  pavement.  Additional  fine  hot  gravel  will  then 
be  poured  along  the  joints,  and  will  be  consolidated  by  tapping 
with  a  light  rammer.  If  found  necessary  additional  paving  cement 
will  be  poured  between  the  blocks  until  the  joints  are  thoroughly 
filled. 

In  measuring  this  work  for  payment,  when  standard  size  gran- 
ite blocks  are  used,  the  area  included  between  the  outer  edge  of 
the  rail  and  a  line  parallel  to  and  six  inches  from  rail  will  be  taken 
as  the  area  of  granite-block  pavement  laid.  Bids  will  be  based  on 
this  rule.  When  so  ordered,  the  block  pavements  will  be  extended 
to  cover  the  entire  area  included  between  the  rail  and  parallel  to 


190  HIGHWAY    CONSTRUCTION. 

and  2  feet  distant  from  said  rail.  In  case  the  tracks  are  laid  with, 
a  grooved  girder  rail,  these  headers  and  stretchers  may  be  omitted 
•if  so  ordered  by  the  engineer,  and  the  asphalt  pavement  laid  close 
to  the  rail. 

(11)  The  work  of  laying  the  asphalt  shall  not  begin  until  the 
curbstones,  crosswalks,  catch-basins,  manhole  heads,  etc.,  have  been 
properly  adjusted  to  the  finished  grade  of  the  street,  and  permis- 
sion to  proceed  has  been  received  from  the  engineer. 

(12)  Interpretation  of  specifications. 

(13)  Omissions  in  specifications. 

(14)  Engineer  defined. 

(15)  Contractor  defined. 

(16)  Notice  to  contractors,  how  served. 

(17)  Preservation  of  engineer's  marks,  etc. 

(18)  Dismissal  of  incompetent  persons. 

(19)  Quality  of  materials. 

(20)  Samples. 

(21)  Inspectors.* 

(22)  Defective  work,  responsibility  for. 

(23)  Measurements. 

(24)  Partial  payments. 

(25)  Commencement  of  work. 

(26)  Time  of  completion. 

(27)  Forfeiture  of  contract. 

(28)  Damages  for  non-completion. 

(29)  Evidence  of  the  payment  of  claims. 

(30)  Protection  of  persons  and  property.  ,  ;: 

(31)  Indemnification  for  patent  claims. 

(32)  Indemnity  bond. 

(33)  Bond  for  faithful  performance  of  work. 

(34)  Power  to  suspend  work. 

(35)  Right  to  construct  sewers,  etc. 

(36)  Loss  and  damage. 

(37)  Old  materials,  disposal  of. 

(38)  Cleaning  up. 

(39)  Personal  attention  of  contractor. 

(40)  Payment  of  workmen. 

*  An  inspector  should  be  placed  at  the  plant  of  the  contractor,  to  know 
what  course  is  pursued  ;  otherwise  the  municipality  has  no  data  for  studying 
the  various  mixtures  nor  does  it  know  that  the  contractor  is  carrying  out  the 
specifications. 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  191 

(41)  Prices. 

(42)  Security  retained  for  repairs. 

(43)  Payment  when  made,  final  acceptance. 

263.  Specifications  for  Asphalt  Pavement  on  Bituminous  Base.— 
Combination  asphalt  pavement  on  bituminous  base  will  consist  of 
a  base  4  inches,  a  binder  of  1|  inches,  and  a  wearing  surface  of  1£ 
inches  in  thickness,  when  compacted. 

The  space  over  which  the  pavement  is  to  be  laid  will  be  ex- 
cavated to  the  depth  of  7  inches  below  the  top  of  the  surface  of  the 
pavement  when  completed.  Any  objectionable  or  unsuitable  ma- 
terial below  the  bed  must  be  removed,  and  the  space  filled  exactly 
parallel  to  the  surface  of  the  new  pavement  when  completed;  and 
the  entire  roadbed  will  be  thoroughly  rolled  with  a  heavy  steam- 
roller weighing  not  less  than  5  tons.  Upon  the  foundation  will 
be  laid  the  base  and  binder,  5^  inches  in  thickness,  in  the  following 
manner : 

Base.— The  base  will  be  composed  of  clean  broken  stone  that 
will  pass  through  a  3-inch  ring,  well  rammed  and  rolled  with  a 
steam-roller  weighing  not  less  than  5  tons,  to  a  depth  of  4  inches* 
The  rolling  will  be  continued  until  the  stone  ceases  to  creep  before 
the  roller,  and  until  it  is  evident  that  the  final  compression  has. 
been  reached.  It  will  be  thoroughly  coated  with  No.  4£  coal-tar 
paving  cement  in  the  proportion  of  about  one  gallon  to  the  square 
yard  of  base. 

Binder. — The  second  or  binder  course  will  be  composed  of 
clean  broken  stone,  thoroughly  screened,  not  exceeding  1  inch  in 
the  largest  dimension,  and  No.  4  coal-tar  paving-cement.  The 
stone  will  be  heated  to  a  temperature  between  230  and  250  degrees 
Fahr.,  by  passing  through  revolving  heaters,  and  thoroughly  mixed 
by  machinery  with  the  paving-cement  in  about  the  proportion  of 
one  gallon  of  No.  4  tar  to  one  cubic  foot  of  stone.  It  will  be 
hauled  upon  the  work,  spread  upon  the  base  course  to  such  thick- 
ness that  when  compacted  it  will  be  1J  inches  thick,  and  immedi- 
ately rammed  and  rolled  with  hand  and  steam  rollers  while  m  a 
hot  plastic  condition. 

Wearing  Surface.— The  wearing  surface  will  be  H  inches  thick 
when  compacted,  and  will  conform  in  all  other  respects  to  the 
wearing  surfaces  as  prescribed  for  the  standard  asphalt  pavement, 
as  described  in  these  specifications. 


192  HIGHWAY    CONSTRUCTION. 

The  pavement  so  constructed  must  be  a  solid  mass,  7  inches 
thick,  and  must  be  thoroughly  rolled  and  cross-rolled  until  it  has 
become  hard  and  solid. 

Gutters,  wherever  directed,  will  be  formed  of  granite-block  or 
brick,  of  such  width  as  may  be  directed,  laid  upon  a  hydraulic  base 
of  not  less  than  4  inches  in  thickness,  in  accordance  with  the  speci- 
fications for  granite-block  pavement  and  for  brick  gutters. 

264.  Specifications  for  Asphalt  Pavement  on  Hydraulic  Base. — 
The  asphalt  pavement  on  hydraulic  base  will  be  7  inches  in  thick- 
ness, consisting  of  a  base  composed  of  4  inches  of  hydraulic  con- 
crete and  2  inches  of  binder,  1J  inches  when  compacted,  and  a 
wearing  surface  of  standard  asphalt',  2J  inches  in  thickness,  or  1| 
inches  when  compacted. 

Binder  Course. — The  binder  course  will  conform  in  all  respects 
to  the  binder  course  for  the  asphalt  pavement  on  bituminious  base, 
and  will  be  1J  inches  in  thickness  when  compacted. 

Wearing  Surface.— The  wearing  surface  will  be  1J  inches  thick 
when  compacted,  and  will  conform  in  all  other  respects  to  the  wear- 
ing surfaces  as  prescribed  for  the  standard  asphalt-pavement. 

264a.  Specifications  for  Asphalt  Pavement  on  the  Surface  of  an 
Old  Pavement. — The  surface  of  the  old  pavement  shall  be  thor- 
oughly cleansed  by  sweeping  with  stiff  brooms  until  all  the  dirt,  etc., 
has  been  removed  from  the  surface  and  from  the •  joints  to  a  depth 
of  about  one  inch. 

The  surface  shall  then  be  brought  to  a  uniform  grade  and  cross- 
section  by  excavating  where  necessary,  and  by  filling  and  repairing 
all  depressions  with  bituminous  concrete  or  binder,  this  binder  to 
be  composed  of  clean  broken  stone,  the  fragments  of  which  shall 
not  exceed  one  and  one  quarter  inches  in  their  largest  dimensions, 
and  asphaltic  pavement  cement  (or  coal-tar  paving-pitch). 

The  stone  shall  be  heated  in  suitable  heating  apparatus,  and 
shall  be  thoroughly  mixed  with  the  paving  cement  in  the  propor- 
tion of  12  to  15  per  cent  of  asphalt  paving  cement  (or  one  gallon 
of  paving-pitch)  to  one  cubic  foot  of  stone. 

This  binder  shall  be  spread  to  such  thickness  that,  after  being 
thoroughly  compacted  by  tamping  and  rolling,  its  thickness  shall 
be  not  less  than  one  inch,  and  its  surface  shall  be  exactly  parallel 
with  the  surface  of  the  pavement  to  be  laid  upon  it. 

Upon  this  foundation  the  wearing  surface  or  pavement  proper 
of  asphaltic  cement  shall  be  laid.  (See  also  Articles  262,  263,264.) 


ASPHALTUM   AND   COAL-TAB   PAVEMENTS.  193 

264b.  Specifications  for  Asphalt  Pavement,  Washington,  D.  C., 
1899. — Binder, — The  binder  course  shall  be  composed  of  clean, 
sound  stone  broken  into  fragments  of  such  size  that  85  per  cent  of 
the  whole  amount  will  pass  through  a  screen  having  1^-inch 
meshes,  and  of  the  remaining  15  per  cent  no  piece  shall  have  a 
larger  dimension  than  2  inches,  and  the  stone  after  passing  the 
heating-drums  shall  not  contain  less  than  5  nor  more  than  10  per 
cent  of  material  passing  a  No.  10  screen. 

The  stone  shall  be  heated  not  higher  than  -350°  F.  in  suitable 
apparatus.  It  shall  then  be  mixed  thoroughly  by  machinery  with 
the  asphaltic  cement,  which  shall  be  of  the  same  quality  as  that 
used  for  the  wearing  surface,  and  having  a  penetration  on  Bowen's 
scale  of  100°  to  200°,  in  such  proportions  that  the  mixture  will 
have  life  and  gloss  without  an  excess  of  cement.  Should  it  appear 
dull  from  overheating  or  lack  of  cement,  it  will  be  rejected. 
While  hot  it  will  be  hauled  upon  the  work,  spread  upon  the  base 
to  such  depth  that  when  compacted  it  will  be  at  least  1^  inches  in 
thickness,  and  immediately  rammed  and  rolled  until  it  is  cold. 
Should  the  resulting  course  not  show  a  proper  bond,  it  shall  be 
immediately  removed  and  replaced  by  the  contractor. 

Asphaltum. — The  crude  asphaltum  shall  be  refined  to  the  satis- 
faction of  the  engineer. 

Flux. — Petroleum  residuum,  Pittsburg  flux,  maltha,  or  any 
other  softening  agent  complying  with  the  required  tests  may  be 
used.  (See  Art.  97 'd  for  specifications  of  petroleum  residuum.) 

Asphaltic  Cement. — When  the  refined  asphaltum  is  not  already 
of  the  proper  consistency  the  cement  shall  be  prepared  by  temper- 
ing refined  asphaltum  with  petroleum  residuum  or  other  approved 
softening  agent,  at  a  temperature  between  250°  and  350°  F. 
The  asphalt  cement  must  not  be  inferior  in  quality  to  a  cement 
made  of  the  best  quality  Trinidad  asphalt  and  petroleum  re- 
siduum. Its  penetration  must  be  within  the  range  of  60°  and  120° 
on  Bowen's  scale,  and  will  be  fixed  by  the  engineer.  A  variation 
of  10°  from  the  degree  decided  upon  will  be  sufficient  for  rejecting 
the  mixture.  .  ^ 

Samples  of  the  asphalt,  flux,  and  asphaltic  cement  must  be: 
furnished  the  engineer  as  required. 

Sand. — The  sand  used  shall  be  hard  and  moderately  sharp. 


194  HIGHWAY    CONSTRUCTION. 

On  sifting,,  at  least  15  per  cent  should  be  retained  in  a  40-mesh-per- 
inch  sieve,  25  per  cent  that  will  pass  80-mesh-to-the-inch  sieve,  10 
per  cent  of  which  at  least  must  pass  a  100-mesh-to-the-inch  sieve. 
If  the  sand  does  not  contain  the  desired  fine  material,  limestone 
dust  or  other  suitable  material  can  be  added  to  make  up  the 
deficiency. 

Inorganic  Dust. — This  shall  be  any  inorganic  dust  not  acted 
upon  by  water,  the  whole  of  which  shall  pass  a  30-mesh  screen  and 
at  least  75  per  cent  pass  a  100-mesh  screen. 

Manufacture  of  the  Paving  Mixture. — The  materials  comply- 
ing with  the  above  specifications  shall  be  mixed  in  proportions  by 
weight,  depending  upon  their  character  and  the  traffic  on  the 
street  and  upon  the  character  of  the  asphalt,  determined  by  the 
engineer,  but  the  percentage  of  bitumen  in  any  mixture  soluble  in 
carbon  bisulphide  shall  not  exceed  the  limits,  9  to  13  per  cent. 
If  the  proportions  of  the  mixtures  are  varied  in  any  manner  from 
those  decided  upon,  the  mixture  will  be  condemned,  its  use  will 
not  be  permitted,  and  if  already  placed  on  the  street  it  will  be 
removed  and  replaced  by  proper  materials  at  the  expense  of  the 
contractor. 

The  sand  or  the  mixture  of  sand  and  stone  dust  and  the 
asphaltic  cement  will  be  heated  separately  to  about  300°  F.  The 
dust,  while  cold,  will  be  mixed  with  the  hot  sand  in  the  required 
proportion  and  then  mixed  with  the  asphaltic  cement  at  the 
required  temperature  and  in  the  proper  proportion,  in  a  suitable 
apparatus,  so  as  to  effect  a  thoroughly  homogeneous  mixture. 
Sand-boxes  and  asphalt-gauges  will  be  weighed  in  presence  of 
inspectors  as  often  as  may  be  desired. 

Samples  as  desired  shall  be  furnished  the  inspector  in  suitable 
boxes,  and  he  shall  .have  access  to  all  branches  of  the  works  at  all 
times. 

265.  Maintenance  of  Asphalt  Pavements  under  Contract. — The 
contractors  will  furnish  all  the  labor  and  materials  necessary  to 
make  repairs  and  renewals  required  to  preserve  the  surface  in  a 
perfect  state,  true  to  the  profile,  without  humps  or  depressions, 
even  if  the  dilapidations  are  the  result  of  accidental  causes>  as  sink- 
ing of  the  subsoil,  etc.,  except  only  the  digging  of  trenches.  The 
contractor  must  renew  all  places  where  the  surface  is  cracked,  split, 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  195 

depressed,  swelled,  or  in  any  way  perforated,  where  it  matches  un- 
evenly with  manhole  heads  and  other  street  fixtures,  etc.,  and 
especially  where  sunken  near  trenches. 

Where  the  foundation  is  defective,  it  shall  be  removed  and  re- 
placed with  good  material.  Defective  spots  must  be  carefully  cut 
out  with  a  sharp  tool,  and  at  least  2  feet  larger  in  every  direction 
than  the  defective  place;  the  sides  must  be  cut  on  straight  lines  ; 
there  must  be  a  perfect  union  of  the  old  and  new  material,  and  the 
surface  must  show  no  irregularities. 

On  September  1st,  or  sooner  in  case  of  bad  weather,  a  general 
examination  will  be  made  with  the  contractor,  who  must  immedi- 
ately begin  repairs  on  doubtful  surfaces,  not  likely  to  endure 
through  the  winter.  In  rainy  weather  the  bottoms  of  patches 
must  be  sponged  and  dried  as  carefully  as  possible  with  fine  hot 
ashes,  and  then  be  well  brushed.  Special  care  must  be  taken  to 
clean  all  sand,  powder,  etc.,  from  the  bottom  of  patches. 

During  bad  weather  no  repairs  shall  be  made  to  the  asphalt, 
unless  expressly  authorized  by  the  engineer.  Patches  made  during 
winter  are  to  be  considered  as  only  temporary,  and  must  be  replaced 
by  the  15th  of  May. 

The  contractor  is  absolutely  forbidden  to  use  pebbles  for  filling 
holes  in  the  asphalt.  When  the  contractor  fails  to  make  the  neces- 
sary repairs,  and  the  administration,  exceptionally  and  in  default 
of  other  available  means,  fills  the  holes  with  broken  stone  or  other 
material,  the  contractor  must  pay  for  the  work  and  materials,  and 
cannot  claim  damages  for  injury  to  the  pavement  caused  by  such 
materials. 

In  winter,  holes  in  the  foundation  may  be  filled  with  a  mixture 
of  3  parts  by  volume  of  pebbles  to  1  part  of  hot  asphalt;  but  this, 
provisional  filling  must  be  removed  as  soon  as  possible  and  replaced 
in  the  standard  manner. 

The  contractor  will  be  paid  for  repairs  to  all  trenches  opened  in 
the  street.  He  can,  however,  make  no  claim  for  settlement  or  any 
other  injury  at  these  places,  and  must  maintain  the  pavement  there 
in  the  same  condition  as  elsewhere. 

To  secure  a  perfect  welding  at  the  edges  of  the  asphalt,  a  width, 
of  2  inches  greater  in  every  direction  than  the  trench  will  be 
paid  for. 

To  provide  for  settlement  of  the  earth  in  the  trenches,  the  con- 
tractor may  maintain  the  area  occupied  by  the  trench,  during  a 


196  HIGHWAY    CONSTRUCTION. 

period  of  eight  days,  with  broken  stone  or  gravel,  well  rammed, 
sprinkled,  swept,  and  maintained,  so  as  to  prevent  injury  to  horses. 
If  after  eight  days  final  repairs  are  still  impossible,  the  contractor 
must  at  his  own  expense  make  a  provisional  surface  of  bituminous 
concrete,  which  will  be  removed  for  final  repairs. 

If  for  any  reason  it  becomes  necessary  to  tear  up  asphalt  pave- 
ments, it  shall  be  done  as  follows :  It  will  be  cut  in  as  straight  lines 
as  possible  with  sharp  chisels,  and  when  torn  up  must  on  no  ac- 
count pull  up  with  it  any  of  the  adjacent  material. 

Then  the  concrete  is  to  be  cut  by  sharp  chisels  in  lines  about  3 
inches  from  the  edge  of  the  asphalt,  which  may  be  broken  into 
pieces  and  laid  aside. 

In  removing  the  earth  from  the  excavation,  care  must  be  taken 
that  no  portion  of  the  concrete  is  undermined. 

265a.  The  "  Bermudez  "  Asphalt,  recently  introduced  for  paving 
purposes,  is  obtained  from  a  lake  or  deposit  which  covers  an  area 
of  several  hundred  acres  in  the  state  of  Bermudez,  Venezuela, 
.S.  A.  (See  also  Art.  101.) 

The  purity  and  quality  are  said  to  be  exceedingly  high;  the  fol- 
lowing analysis  is  given  by  Prof.  E.  J.  De  Smedt : 

Bitumen  soluble  in  CS2 97.86  per  cent 

Organic  and  inorganic  matter  (impurities) 2.14        " 

100.00  per  cent 

The  following  are  some  of  the  characteristics  of  this  asphalt : 

At  60°  F.  compressible;  at  70°  F.  viscous  and  malleable;  at 
100°  F.  flowing,  and  can  be  stretched  in  hair-like  threads;  at 
189°  F.  melts;  at  400°  F.  gives  no  flash. 

The  paving-cement  is  manufactured  by  adding  15  Ibs.  of  re- 
siduum oil,  20  Baume  at  60°  F.,  to  each  100  Ibs.  of  refined  asphalt. 
This  100  Ibs.  of  refined  asphalt  yields  97. 06  Ibs.  of  pure  bitumen; 
consequently  13T3<j-  per  cent  of  oil  is  added  to  the  pure  bitumen. 

The  asphalt  is  melted  at  from  250°  to  300°  F.  The  oil  is  then 
added  and  thoroughly  mixed  with  the  melted  asphalt. 

The  pavement  mixture  is  composed  of  the  following  materials 
and  in  the  proportions  stated : 

Aspbaltic  cement 9  to    10  parts 

Pulverized  carbonate  of  lime 20"    30     " 

Fine  clean  sand 71"    60    " 

100     100 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  197 

The  sand  and  carbonate  of  lime  are  mixed  and  heated  to 
from  250°  to  300°  F.  The  asphaltic  cement  is  heated  separately 
to  from  225°  to  250°  F.  The  materials  so  heated  are  mixed  in  a 
suitable  mixing  apparatus,  and  the  mixture  while  at  a  temperature 
not  below  200°  F.  is  spread  upon  the  foundation  in  two  coats,  the 
lower  or  cushion  coat  being  one-half  inch  thick  after  compression, 
and  the  second  or  wearing  coat  being  two  inches  thick  after  final 
compression  with  a  roller  weighing  not  less  than  250  Ibs.  per  inch 
run.  A  small  amount  of  hydraulic  cement  is  swept  over  the  surface 
before  the  application  of  the  roller. 

It  is  claimed  that  pavements  made  from  this  asphalt  do  not  rot 
in  contact  with  water. 

One  square  yard  of  pavement  2 J  inches  thick  weighs  250  Ibs. 

266.  European  Asphalt  Pavements. — In  Paris  two  kinds  of  as- 
phalt pavement  are   employed.     First,  asphalt  coule,  made  from 
natural  rock  asphalt  to  which  is  added  sufficient  bitumen  to  make 
the  total  15  to  18  per  cent  of  bitumen.    The  mass  is  heated  for  about 
six  hours  so  as  to  make  a  thorough  mixture.     The  ground  having 
been  graded,  sprinkled  and  thoroughly  rammed  or  rolled,  a  bed  of 
hydraulic-cement  concrete  from  4  to  6  inches  thick  is  laid,  and  after 
this  is  set  and  well  dried  the  asphalt  mixture  is  spread  and  surfaced 
by  a  wooden  float.     The  thickness  of  the  asphalt  is  about  \\  inches, 
and  it  is  usually  applied  in  two  layers.     This  covering  will  not 
soften  at  a  temperature  of  140  degrees  Fahr. 

267.  The  second  kind  of  asphalt  covering  is  asphalt  comprime, 
or  compressed  asphalt.     In  this  the  natural  rock  alone  is  used.  It 
comes  from  Val  de  Travers  in  Switzerland,  Seyssel  in  France,  and 
other  localities,  and  consists  of  carbonate  of  lime  impregnated  with 
bitumen.     The  color  is   a  dark    (almost  black)  chocolate-brown. 
When  cold  the  rock  breaks  easily,  with  an  irregular  fracture  and 
without  definite  cleavage.     Its  grain  should  be  regular  and  homo- 
geneous; the  finer  the  grain  the  better.   When  exposed  to  the  atmos- 
phere the  bituminous  rock  gradually  assumes  a  gray  tint,  by  reason 
of  the  bitumen  evaporating  from  the  surface,  leaving  a  thin  film  of 
limestone  behind. 

268.  The   following  is  a   test    for  bituminous  rock   given  by 
Mr.  Delano  in  a  paper  he  read  before  the  Institution  of  Civil  En- 
gineers in  the  year  1880.     "  A  specimen  of  the  rock,  freed  from  all 


198  HIGHWAY    CONSTRUCTION. 

extraneous  matter,  having  been  pulverized  as  finely  as  possible, 
should  be  dissolved  in  sulphurate  of  carbon,  turpentine,  ether,  or 
benzine,  placed  in  a  glass  vessel  and  stirred  with  a  glass  rod.  A  dark 
solution  will  result  from  which  will  be  precipitated  the  limestone. 
The  solution  of  bitumen  should  then  be  poured  off.  The  dissolvent 
speedily  evaporates,  leaving  the  constituent  parts  of  the  bitumen, 
each  of  which  should  be  weighed  so  as  to  determine  the  exact 
proportion.  The  bitumen  should  be  heated  in  a  lead  bath  and 
tested  with  a  porcelain  or  Baume  thermometer  to  42 8  degrees  Fahr. 
There  will  be  little  loss  by  evaporation  if  the  bitumen  is  good,  but 
if  bituminous  oil  is  present  the  loss  will  be  considerable.  Gritted 
mastic  should  be  heated  to  450  degrees  Fahr.  The  limestone  should 
be  next  examined.  If  the  powder  is  white  and  soft  to  the  touch,  it 
is  a  good  component  part  of  asphalt;  but  if  rough  and  dirty, on 
being  tested  with  reagents  it  will  be  found  to  contain  iron  pyrites, 
silicates,  clay,  etc.  Some  bituminous  rocks  are  of  a  spongy  or  hygro- 
metrical  nature;  thus,  as  an  analysis  which  merely  gives  so  much 
bitumen  and  so  much  limestone  may  mislead,  it  is  necessary  to 
know  the  quality  of  the  limestone  and  of  the  bitumen." 

The  European  bituminous  limestone  appears  like  a  fine-grained 
rook,  friable  in  summer,  hard  in  winter.  When  heated  to  50  or  CO 
degrees  (centigrade)  it  can  be  crushed  between  the  fingers,  and  if 
exposed  for  several  hours  to  a  fierce  sun  it  crumbles  into  unctuous 
brown  powder.  Examined  under  the  microscope  it  is  found  to 
consist  of  minute  calcareous  grains,  each  covered  with  a  thin  film 
of  bitumen  which  causes  them  to  adhere  together.  If  a  small  por- 
tion is  heated,  the  cementing  bitumen  is  melted  and  releases  the 
solid  particles  from  a  loose  heap  of  a  deep  chocolate  color.  If 
this  powder  is  raised  to  175  or  212  degrees  Fahr.  and  rapidly  com- 
pressed in  a  mould,  it  will  regain,  in  cooling,  its  original  consistency 
in  the  new  form.  And  the  process  may  be  indefinitely  repeated, 
no  change  being  produced  by  melting,  followed  by  compression 
and  cooling. 

269.  The  best  material  used  by  the  "  Compagnie  Generale  des 
Asphaltes  de  France "  comes  from  the  Pyrimont  mines  of  the 
Seyssel  region  in  the  Department  of  Haute  Savoie  and  Litin, 
France.  The  workings  are  in  great  part  subterranean  and  the 
deposit  lies  in  eight  superimposed  beds  separated  by  beds  of  white 
limestone.  One  of  these  bituminous  beds  lies  about  100  feet  above 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  199 

the  level  of  the  Ehone  and  has  a  thickness  of  23  feet;  it  is  the 
largest  of  all  known  beds  of  this  material.  The  galleries  noi» 
driven  aggregate  about  seven  miles  in  length. 

270.  The  rock  is  extracted  in  a  temperature  ranging  from  53  to 
55  degrees  Fahr.,  and  it  is  relatively  hard.     This  desirable  quality 
can  be  increased  by  taking  it  outside  during  the  winter,  but  it  should 
not  even  then  be  exposed  to  the  sun.     Dynamite  or  gunpowder  is 
used  in  extracting  it,  the  latter  being  used  when  the  mass  is  com- 
pact, dry,  and  without  fissures.     As  the  rock  is  to  a  certain  degree 
plastic,  it  compresses  easily  and  does  not  work  well  with  the  more 
violent  and   quick  explosives.     On  the  other   hand,  dynamite  is 
effectively  used  in  the  wetter  parts   of  the  mine  and   in  places 
where  fissures  would  permit  the  slower-acting  gases  from  gunpow- 
der to  escape  without  efficient  work. 

The  blocks  of  bituminous  rock  are  removed  outside  by  rail  and 
as  few  blocks  as  possible  are  piled  upon  one  car,  to  avoid  crushing 
under  the  effect  of  the  heat  of  the  sun.  This  crushing  is  undesir- 
able for. two  reasons:  first,  there  is  more  waste  in  the  transport  and 
handling;  and  secondly,  if  rain  falls  upon  a  pulverized  mass,  it  ab- 
sorbs water  rapidly  and  becomes  exceedingly  difficult  to  treat. 

271.  The  operations  preliminary  to  the  application  of  the  bitu- 
minous rock  to  the  street  surface  are:  (1)  The  extraction  and  (2) 
the  crushing  of  the  rock.     (3)  The  heating  of  the  powder.     (4) 
Transporting  the  heated  powder  to  the  street.     (5)  Spreading  it 
while  warm.     (6)  Ramming.     (7)  Rolling. 

272.  The   quarried    blocks   of    mineral   are   crushed   between 
toothed  cylinders,  revolving  at  unequal  speeds,  which  reduce  it  to 
pieces  of  the  average  size  of  eggs.     These  are  pulverized  in  "  Carr  " 
machines,  which  run  about  600  revolutions  per  minute,  and  deliver 
it  as  powder,  which  is  sifted  to  uniform  extreme  fineness.     This 
powder  is  heated  in  an  apparatus  resembling  a  "coffee-roaster;" 
the  revolving  cylinder  is  about  6J  feet  in  diameter  and  the  same  in 
length;  the  exterior  envelope  carries  a  chimney,  disposed  in  such 
fashion  that  the  heated  air  from  the  furnace  passes  all  around  the 
cylinder.     The  furnace  itself  is  movable  and  placed  immediately 
below  the  cylinder,  and  rests  on  a  railway  so  that  it  may  be  run  out 
of  the  way.     The  moving  cylinder  is  mounted  upon  an  axle  and 
supported  on  journals  in  the  enveloping  cylinder,  which  rests  upon 
four  stout  legs. 


200  HIGHWAY   CONSTRUCTION. 

273.  The  powder  is  put  into  the  roaster  by  means  of  a  hopper 
placed  opposite  a  central  hole  forming  an  annular  space  around 
the  axle.    The  powder  falls  into  the  cylinder,  which  is  moving  very 
slowly;  the  cylinder  is  provided  with  interior  blades  arranged  in  a 
spiral,  by  which  the  contents  are  lifted  up  to  the  top  and  fall  in  a 
shower  through  the  hot  air  in  the  cylinder,  until  it  is  thoroughly 
warmed  both  by  this  action  and  by  contact  with  the  hot  sides  of 
the  cylinder.    As  the  movement  of  the  cylinder  is  perfectly  regular, 
the  powder  remains  on  the  blades  only  a  determinable  time,  and 
the  entire  mass  has  imparted  to  it  a  uniform  temperature.     The 
apparatus  used  on  the  work  of  the  city  of  Paris  heat,  to  a  tempera- 
ture of  about  300  degrees  Fahr.,  about  3960  pounds  of  powder 
in  15  minutes. 

When  the  powder  is  sufficiently  heated  the  furnace  is  run  out 
from  under  it,  and  is  replaced  by  the  special  wagon  used  for  trans- 
porting the  warm  powder  to  the  place  of  use,  into  which  the 
powder  falls  after  opening  a  gate  in  the  side  of  the  cylinder. 

274.  Asphaltum  is  a  bad  conductor  of  heat,  and  this  negative 
quality  much  simplifies  the  difficulties  of  its  preparation,  and  per- 
mits the  material  to  be  heated  at  central  stations  and  conveyed  a 
considerable  distance  before  it  will  fall  appreciably  in  temperature ; 
in  fact,  the  powder  loaded  into  sheet-iron  carts  with  double  sides 
and  cover  may  be  carried  from  1J  to  9|  miles  from  the  place  of 
heating  to  the  place  of  use  without  losing  on  the  way  more  than 
35  or  40  degrees  Fahr.  of  its  mean  temperature. 

275.  The  hot  material  is  emptied  out  on  the  concrete  founda- 
tion, spread  by  hot  rakes  in  a  layer  of  sufficient  thickness  to  allow 
for  compression  to  the  exact  finished  surface  and  required  thick- 
ness, viz.,  about  3  inches  for  a  2-inch  coat. 

The  surface,  and  consequently  the  thickness,  is  regulated  by  a 
wooden  straight-edge  bearing  on  parallel  guides  set  at  the  required 
height  in  the  surface  of  the  concrete. 

276.  The   ramming  is  done  by  round  cast-iron  rams,  6  to  8- 
inches  in  diameter.,  which   are  used   by  fifteen    or  twenty  men, 
marching  side  by  side  and  vigorously  ramming  the  asphalt  while 
it  is  yet  hot.     After  a  few  minutes  a  roller  drawn  by  two  men  and 
heated  by  an  internal  furnace  gives  what  is  called  the  "  primary 
compression,"  the   normal  compression  being  effected  under  the- 
traffic  by  the  carriage-wheels.     During  the  rolling  a  small  quantity 


ASPHALTUM-AND    COAL-TAR   PAVEMENTS.  201 


of  hydraulic  cement  is  strewn  over  the  surface.     The  rolling  is  con- 
tinued until  the  asphalt  is  cold. 

The  bituminous  limestone  to  form  a  good  roadway  pavement 
should  contain  from  9  to  10  per  cent  of  bitumen,  and  be  non-evap- 
orative at  428°  Fahr.  Limestones  containing  much  more  than  10 
per  cent  of  bitumen  become  soft  and  wavy  in  summer;  those  Con- 
taining much  less  have  not  sufficient  binding  power  to  sustain 
heavy  traffic. 

277.  Bituminous  Limestone  Pavements  in  the   United  States. 
—About  55,000  square  yards  of  bituminous  limestone  pavement 
were  laid  in  Washington,  D.  C.,  during  1876  and  1887,  and  about 
3000  square  yards  in  New  York  in  1883  or  1884;  nearly  all  of  this 
was  subsequently  taken  up  and  replaced  by  Trinidad  asphalt.     In 

1887  about  10,000  square  yards  were  laid  in  Rochester,  N.  Y.;  in 

1888  about  20,000  square  yards  in  St.  Augustine,  Florida;  and  in 
1890  40,000  square  yards  in  New  York  City.     The  total  amount  of 
bituminous  limestone  pavements  now  in  use  in  the  United  States 
is  estimated  at  75,000  square  yards. 

These  pavements  are  composed  of  a  mixture  of  about  three 
parts  of  bituminous  limestone  rock  from  Ragusa,  Sicily,  and  one 
part  of  a  similar  rock  from  Vorwohle,  Germany;  the  latter  is  a 
harder  rock  and  contains  less  bitumen  than  the  Sicilian. 

The  paving  mixture  contains  from  10  to  12  per  cent  of  bi- 
tumen, and  is  prepared  by  pulverizing  the  mixed  rock  and  heating 
it  to  a  temperature  of  about  100°  Fahr.  The  heated  powder  is  laid 
and  compressed  in  the  manner  described  under  European  Asphalt 
Pavements. 

278.  Coal-tar  Pavements.* — The  wearing  surface  of  the  earlier 
pavements  was  made  in  various  ways,  according  to  the  patent,  but 
consisted  essentially  of  small  gravel,  sand,  and  stone-dust,  cemented 
by  a  product  of  coal-tar.     In  the  later  pavements  of  this  variety  a 
certain  proportion  of  bitumen  is  mixed  with  the  tar,  and   with 
beneficial  results. 

*The  Report  of  the  Engineer  Department  of  the  District  of  Columbia  for 
1898  says  regarding  tar  pavements:  "This  pavement  answers  the  purpose 
well  during  hot  weather,  but  as  soon  as  the  temperature  becomes  low  enough 
to  cause  the  tar  to  become  brittle,  it  goes  to  pieces  with  but  little  more  cohe- 
sion than  so  much  loose  gravel  or  broken  stone." 


202  HIGHWAY    CONSTRUCTION. 

Wherever  laid  in  the  United  States,  coal-tar  pavements,  as  a  rule, 
have  given  little  satisfaction,  their  failure  being  due  to  the  pres- 
ence of  volatile  oils  in  the  tar,  which  on  exposure  to  atmospheric 
influence  slowly  oxidize  and  become  inert,  thus  destroying  the 
cementing  qualities  of  the  tar.  If  these  oils  are  removed  before 
the  tar  is  used  the  resulting  material  is  brittle,  and  soon  crumbles 
to  pieces  after  being  laid.  Coal-tar  is  also  very  sensitive  to  heat :  in 
summer  it  is  soft,  in  winter  brittle.  On  account  of  these  defects, 
the  use  of  coal-tar  alone,  as  a  cementing  material  for  pavements, 
has  been  almost  entirely  abandoned. 

279.  Coal-tar  and  Asphalt. — To  overcome  the  defects  of  coal-tar 
when  used  alone,  the  practice  has  arisen  of  mixing  the  gas  tars  with 
bitumen,  and  this  has  been  successful  in  proportion  to  the  amount 
of  the  bitumen  used.     The  most  successful  pavement  of  this  char- 
acter is  that  known  as  the  "  Vulcanite/'    This  pavement  is  prepared 
as  follows : 

280.  Filbert  Vulcanite    Asphalt  Pavement   as    laid    by    the 
National  Vulcanite  Company  of  New  Jersey. — The  pavement  is  83- 
inches  in  thickness,  formed  as  follows :  The  wearing  surface   1£ 
inches  when  compacted,  and  a  bituminous  base  and  binder  7  inches 
in  depth. 

The  base  is  composed  of  stone  broken  to  pass  through  a  3-inch 
ring.  It  is  spread  on  the  earth  surface,  previously  graded  to  receive 
it,  to  a  depth  of  5  inches,  these  consolidated  with  a  steam  roller, 
after  which  it  is  covered  with  a  hot  paving-cement  composed  of  No. 
4  tar  distillate  in  the  proportion  of  about  one  gallon  to  the  square 
yard  of  pavement. 

The  second  or  binder  course  is  composed  of  stone  broken  to  pass 
through  a  1^-inch  ring, — the  stone  being  thoroughly  cleansed  and 
screened, — and  No.  4  tar  distillate.  The  stone  is  heated  by  passing 
through  revolving  heaters,  and  is  thoroughly  mixed  by  machinery 
with  the  distillate  in  the  proportion  of  one  gallon  of  distillate  to  one 
cubic  foot  of  stone. 

The  binder  is  spread  upon  the  base  to  a  depth  of  two  inches, 
and  is  immediately  rammed  and  rolled  with  hand  and  steam  rollers 
while  hot  and  in  a  plastic  condition.  "•'''. 

The  wearing  surface,  1  i  inches  thick,  is  made  of  paving-cement, 
composed  of  25  per  cent  of  asphalt  and  75  per  cent  of  tar  distillate, 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  203 

and  clean  sharp  sand  and  stone  pulverized  to  pass  through  a  ^-inch 
ring  in  the  proportion  of  two  parts  of  sand  to  one  part  of  stone. 

To  21  cubic  feet  of  the  above  ingredients  are  added  one  peck  of 
hydraulic  cement,  one  quart  of  flour  of  sulphur,  and  two  quarts  of 
air-slaked  lime.  To  this  mixture  is  added  320  pounds  of  paving- 
cement. 

The  materials  above  described  are  heated  to  about  250  degrees 
Fahr. — the  paving  cement  in  kettles,  the  sand,  stone,  etc.,  in  revolv- 
ing heaters — then  thoroughly  mixed  by  machinery,  carried  to  the 
street,  and  spread  on  the  binder  course  to  a  depth  of  two  inches. 
While  hot  and  plastic  it  is  rolled  with  a  steam  roller,  hydraulic 
cement  being  dusted  over  the  surface.  The  rolling  is  continued 
until  the  roller  ceases  to  leave  an  impression  on  the  surface. 

281.  Advantages  of  Coal-tar  and  Asphalt  or  Distillate  Pavement. 

(1)  It  is  cheap. 

(2)  Its  surface  is  more  granular  and  less  slippery  than  asphalt. 

(3)  The   binder  binds   the   base   and   wearing  surface   firmly 
together  and  eliminates  to  a  great  extent  the  faults,  of  weather 
cracks  and  wave-surfaces. 

(4)  It  can  be  laid  from  curb  to  curb,  as  it  will  not  "rot"  in  the 
gutters  as  does  the  asphalt. 

(5)  Pavements  constructed  of  carefully  selected  and  combined 
materials  and  properly  laid  will  cost  but  little,  if  any,  more  than 
the  asphalt  for  maintenance. 

282.  Defects  of  Coal-tar  and  Asphalt  Pavement. 

(1)  The  wearing  surface  consists  of   75  per  cent  of  coal-tar, 
which  material  can  rarely  be  obtained  of  uniform  quality. 

(2)  The  wearing  -surface,  being  only  1£  inches  thick,  requires 
renewal  at  frequent  intervals. 

(3)  The  pavement  is  not  so  pleasing  to  the  eye  as  asphalt  in 
color. 

(4)  The  use  of  the  bituminous  base  gives  rise  to  many  per- 
plexing problems  in  the  grade  of  the  streets  on  which  it  is  used,  due 
to  the  fact  that  the  base,  the  binder,  and  the  wearing  surface  co- 
alesce so  as  to  form  a  solid  mass.     The  wear  on  the  surface  is  never 
quite  uniform;  and  when  the  binder  or  base  becomes  exposed  on  the 
moat  travelled  part  of  the  street,  the  pavement  near  the  gutter  may 
be  worn  but  slightly.     To  resurface  properly,  the  remnants  of  the 
old  surface  should  be  removed,  and  the  new  surface  laid  directly 


204  HIGHWAY   CONSTBUCTIOK. 

upon  the  binder.  It  is,  however,  impracticable  to  strip  a  coal-tar 
surface.  It  may  be  broken  by  the  pick  and  bar,  but  it  breaks  as 
readily  in  the  base  or  binder  as  at  the  original  line  of  demarcation. 
In  fact,  there  is  no  such  line.  The  practice  is  to  cut  out  what  may 
be  necessary  near  the  curb  and  put  a  new  surface  on  the  roadway 
as  it  stands.  The  result  is  to  raise  the  level  of  the  roadway  at  every 
resurfacing,  or,  if  the  original  level  at  the  curb  be  maintained  by  the 
method  of  cutting  out  as  stated,  to  increase  the  crown  of  the  street; 
but  as  such  pavements  will  not,  as  a  rule,  require  resurfacing  at 
more  frequent  intervals  than  every  fifteen  years,  and  as  the  surfac- 
ing should  not  raise  the  level  more  than  one-half  inch,  the  upward 
growth  will  not  exceed  3i  inches  per  century. 

If   the   surface   is   tarred   over  every  year  with  a  brush  and 
sprinkled  with  sand,  the  life  is  lengthened. 

283.  Asphalt  and  Coal-tar  or  Distillate  Pavements  in  Washing- 
ton, D.  C.     (Extract  from  the  Keport  of  Capt.  E.  Griffin,  United 
States  Engineers,  Assistant  to  the  Engineer  Commissioners,  for  the 
year  ending  June  30,  1887.) — During  the  year  1886-1887  six  per 
cent  of  the  new  pavements  laid  was  sheet  coal-tar  distillate.     As 
this  is  the  first  year  since  the  organization  of  the  present  form  of 
District  government  that  coal-tar  distillate  pavements  have  been 
laid  in  the  streets  of  Washington,  a  few  words  in  this  connection 
will  not  be  inappropriate.     Previous  to  1878,  745,305  square  yards 
of  coal-tar  pavements  of  various  kinds  were  laid  at  prices  ranging 
from  $1.74  to  $3.70  per  square  yard.     Many  of  these  pavements 
proved  unreliable,  either  through  inherent  defects  in  the  materials 
used  or  faulty  methods  of  mixing  and  laying.     Some  went  to  pieces 
in  a  few  years,  and  others  deteriorated  so  rapidly  as  to  soon  place 
the  annual  cost  of  maintenance  at  excessively  high  figures.     Of  the 
so-called  Evans  pavement  190,663  square  yards  were  laid,  mostly  in 
1873.     When  only  two  years  old  nearly  all  these  pavements  were 
resurfaced  at  an  average  cost  of  $1.09  per  square  yard. 

284.  As  late  as  1877  Lieutenant  Hoxie  estimated  twenty  cents 
per  yard  per  annum  as  the  cost  of  maintaining  coal-tar  pavements. 

285.  The  average  annual  expenditure  for  maintenance  of  coal- 
tar  pavements  for  the  fifteen  years  ending  June  1, 1886,  has  been  7T2ff 
cents  per  square  yard.     Of  the  Evans  pavement,  157,324  square 
yards  were  resurfaced  by  Scharf  within  two  years  after  being  laid, 
and  virtually  became  Scharf  pavements.    Considering  them  as  such, 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  205 

the  mean  average  annual  expenditure  for  maintenance  was  5J  cents 
per  square  yard.  For  the  first  five  years  the  annual  average  was 
3T7y  cents;  for  the  second  five  years,  6  cents;  for  the  last  five  years, 
•6/0  cents. 

286.  "  That  a  durable  coal-tar  pavement  can  be  laid  is  proven 
by  the  fact  that  the  158,595  square  yards  of  vulcanite  pavements 
liave  only  averaged  2T9g-  cents  per  square  yard  per  annum  for  four- 
teen years'  maintenance,  the  average  being  y3F  cents  per  yard  for 
the  first  five  years,  4T2¥  cents  for  the  second  five  years,  and  4  cents 
for  the  last  four  years. 

287.  The  return  to  the  coal-tar  distillate  pavements  was  virtu- 
ally forced  upon  the  commissioners  by  the  clause  in  the  appropria- 
tion act  for  1886-7  which  "provided"  that   under  this  act  no 
contract  shall  be  made  for  making  or  repairing  concrete  or  asphalt 
pavements  at  a  higher  price  than  $2.00  per  square  yard  for  a  quality 
equal  to  the  best  laid  in  the  District  prior  to  July  1, 1886,  and  with 
same  depth  of  base. 

288.  No  bids  were  received  for  asphalt  pavements  in  response 
to  proposals  advertised  for  under  this  act,  so  a  return  to  distillate 
pavements  was  made. 

289.  In  1888  bids  for  a  modified  asphalt  pavement  were  received, 
and  contracts  have  been  made  to  lay  a  large  proportion  of  the 
streets  with  it  during  the  present  year.     This  modified   asphalt 
pavement    consists  of  a  4-inch  bituminous  base,  1£  inch   binder 
course,  with  a  wearing  surface  of  1^  inches  of  Trinidad  asphalt 
instead  of  1^  inches  of  coal-tar  distillate  composition. 

290.  "Another  modification  of  the  standard  asphalt  pavement 
was  laid  in  Washington  last  year.     This  consists  of  a  base  of  4 
inches  of  hydraulic  concrete,  1|  inches  of  bituminous  binder,  and 
1J  inches  of  asphalt  wearing  surface-coat.     This  is  in  every  respect 
a  most  excellent  pavement,  and  more  ol  it  would  be  laid,  only  the 
contractors  refuse  to  lay  it  for  less  than  $2.10  per  square  ya:?i,  and 
as  the  law  prohibits  the  payment  of  more  than  $2.00  its  use  had 
to  be  discontinued."  (Report  of  Capt.  T.  W.  Symons,  United  States 
Engineers,  Assistant  to  the  Engineer  Commissioners  of  the  District 
af  Columbia  in  1889.) 

291.  Specifications  for  Coal-tar  Distillate  Pavement.— Coal-tar 
distillate  pavement  will  consist  of  a  base  and  binder  of  4£  inches 
in  depth  when  compacted,  and  a  wearing  surface  of  1J  inches  in 


206  HIGHWAY    CONSTRUCTION. 

thickness  when  compacted.  The  space  over  which  the  pavement 
is  to  be  laid  will  be  excavated  to  the  depth  of  6  inches  below  the 
top  of  the  surface  of  the  pavement  when  completed.  Any  objec- 
tionable or  unsuitable  material  below  the  bed  must  be  removed  and 
the  spaces  filled  with  clean  gravel  or  sand  well  rammed.  The  bed 
will  then  be  trimmed  so  as  to  be  exactly  parallel  to  the  surface  of 
the  new  pavement  when  completed,  and  the  entire  roadbed  will  be 
thoroughly  rolled  with  a  heavy  steam  roller.  Upon  this  foundation 
will  be  laid  the  base  and  binder,  4^  inches  in  thickness,  in  the 
following  manner : 

Base. — The  base  will  be  composed  of  clean  broken  stone  that 
will  pass  through  a  3-inch  ring,  well  rammed  and  rolled  with  a 
steam  roller  to  a  depth  of  4  inches,  and  thoroughly  coated  with 
No.  1-J  coal-tar  paving-cement  in  the  proportion  of  about  1  gallon 
to  the  square  yard  of  base. 

Binder. — The  second  or  binder  course  will  be  composed  of  clean 
broken  stone,  thoroughly  screened,  not  exceeding  H  inches  in-  the 
largest  dimension,  and  No.  4  coal-tar  paving-cement.  The  stone 
will  be  heated  to  a  temperature  between  230  and  250  degrees  Fahr., 
by  passing  through  revolving  heaters  and  thoroughly  mixed  by 
machinery,  with  the  paving-cement  in  about  the  proportion  of  1 
gallon  of  No.  4  tar  to  1  cubic  foot  of  stone.  It  will  be  hauled  upon  the 
work,  spread  upon  the  base  course  at  least  2  inches  thick,  and  im- 
mediately rammed  and  rolled  with  hand  and  steam  rollers  while  in 
a  hot  plastic  condition. 

Wearing  Surface. — The  wearing  surface  will  be  composed  of  the 
following  materials  in  the  given  proportions : 

Per  cent. 

Clean  sharp  sand 63  to  58 

Broken  stone  or  rock-dust 28  to  23 

Paving-cement , 13  to  15 

Hydraulic  cement 0.9 

Slaked  lime 0.15 

Flour  of  sulphur 0. 1 

The  sand  shall  be  clean,  sharp  river  sand,  free  from  clay,  and 
of  such  size  that  not  more  than  20  per  cent  shall  be  retained  upon 
a  sieve  of  twenty  meshes  to  the  inch  and  not  more  than  five  per 
cent  shall  pass  through  a  sieve  of  70  meshes  to  the  inch,  about  60 
per  cent  to  be  coarser  than  40  meshes  to  the  inch.  The  broken 


ASPHALTUM    AND    COAL-TAK   PAVEMENTS.  207 

stone  or  stone-dust  shall  be  the  residue  from  the  crushing  of  stone 
from  the  base  and  binder  which  passes  a  sieve  of  not  more  than  6 
meshes  to  the  inch. 

The  paving-cement  shall  be  composed  of  fine  Trinidad  asphalt, 
twenty-five  to  thirty  parts ;  No.  4  coal-tar  paving-cement,  seventy- 
five  to  seventy  parts.  The  refined  asphalt  must  contain  at  least  60 
per  cent  of  pure  bituminous  matter,  soluble  in  carbon  bisulphide. 
The  No.  4  coal-tar  paving-cement  must  correspond  to  a  standard  to 
be  furnished  by  the  engineer,  and  be  free  from  excess  of  sooty  mat- 
ter, naphthaline  and  creosote  oils.  The  hydraulic  cement,  lime,  and 
sulphur  must  be  of  the  best  commercial  quality. 

The  materials  for  the  wearing  surface  will  be  heated  to  not  over 
26  degrees  Fahr.,  the  paving-cement  in  kettles,  the  sand  and  stone- 
dust  in  revolving  heaters.  To  the  latter  the  hydraulic  cement,  lime, 
and  sulphur  will  be  added  cold  in  the  sand-box  before  going  to  the 
mixer.  They  will  be  thoroughly  mixed  by  approved  machinery, 
and  the  mixture  carried  upon  the  work,  where  it  will  be  spread  upon 
the  binder  course  2  inches  thick  with  hot  iron  rakes  and  other 
suitable  appliances,  and  immediately  compacted  with  hot  tamping- 
irons  and  hand  and  steam  rollers,  while  in  a  hot  and  plastic  state. 
In  spreading  the  material  the  joints  are  to  be  diagonal  to  the  line 
of  the  street.  The  surface  will  be  finished  with  a  dusting  of  dry 
hydraulic  cement  rolled  in.  In  cool  weather  or  when  ordered  the 
carts  carrying  the  mixture  are  to  be  protected  with  canvas  covers. 

The  pavement  so  constructed  must  be  a  solid  mass  6  inches 
thick,  and  must  be  thoroughly  rolled  and  cross-rolled  until  it  has 
become  hard  and  solid.  The  relative  proportions  of  the  component 
materials  will  be  changed  upon  the  order  of  the  engineer,  as  occa- 
sion shall  require. 

All  materials,  as  well  as  the  plant  and  methods  of  manufacture, 
will  be  subject  to  the  inspection  and  approval  of  the  engineer. 

The  degree  of  fineness,  both  of  sand,  stone-dust,  and  powdered 
limestone,  will  be  determined  by  testing  with  screens  as  follows: 
The  powdered  carbonate  of  lime  will  be  of  such  degree  of  fineness 
that  16  per  cent  of  weight  shall  be  an  impalpable  powder  of  limestone, 
and  the  whole  of  it  shall  pass  a  No.  26  screen.  The  sand  will  be 
of  such  size  that  no  more  than  50  per  cent  of  it  will  pass  a  No.  80 
screen,  and  the  whole  of  it  shall  pass  a  No.  20  screen.  The  broken 
stone  or  stone-dust  shall  be  the  residue  from  the  crushing  of  stone 


208  HIGHWAY    CONSTRUCTION. 

from  the  base  and  binder  which  passes  a  sieve  of  not  more  than  6 
meshes  to  the  inch. 

Gutters,  wherever  directed,  will  be  granite-block  or  brick,  of  such 
width  as  may  be  directed,  laid  upon  a  hydraulic  base  of  not  less  than 
4  inches  in  thickness,  in  accordance  with  the  specifications  for 
granite-block  pavement  or  brick  gutters. 

292.  Asphalt  Block  Pavements. — The  manufacture  of  paving- 
blocks  from  crushed  stone  and  asphaltic  cement  was  begun  in  San 
Francisco  in  18"69,  but,  in  consequence  of  imperfectly  prepared 
materials  and  crude  appliances,  the  blocks  were  weak  and  friablo 
and  the  results  were  unsatisfactory  ;  since  that  time  to  the  present 
improvements  have  been  made  in  the  processes  and  machinery, 
resulting  in  the  production  of  a  tougher  and  more  enduring  block, 
A  large  amount  of  which  has  been  laid,  particularly  in  Washington 
and  Baltimore. 

Composition. — The  blocks  are  composed  of  crushed  stone  and 
asphaltic  cement  in  the  proportion  of  87  to  90  per  cent  of  stone 
and  13  to  10  per  cent  of  cement. 

The  stone  employed  is  trap,  gneiss,  limestone,  etc. ;  the  stone  is 
broken  and  partially  pulverized  under  crushers  and  rollers  ;  the 
asphaltic  cement  is  prepared  from  any  selected  asphaltum  (usually 
Trinidad  and  California)  in  the  manner  described  in  Art.  96. 

The  composition  of  the  blocks  now  used  in  Washington, 
B.C.,  is: 

Asphaltic  cement 13  per  cent. 

Limestone-dust 10    "      " 

Crushed  gneiss 77    "      " 


100  per  cent. 

(Sand  is  not  used, because  it  has  been  found  to  cut  the  moulds.) 
Manufacture. — The  materials  are  heated  to  a  temperature  of 
300°  F.,  then  thoroughly  combined  in  mechanical  mixers.  As  the 
mixture  leaves  the  mixing  apparatus  it  passes  into  a  pressing 
machine  very  similar  to  that  used  for  pressing  bricks,  and  is 
moulded  and  compressed  while  hot  into  blocks  measuring 
4  X  5  X  12  inches;  the  blocks  are  then  cooled  under  water  and  are 
ready  for  use.  The  blocks  weigh  from  twenty-two  and  a  half  to 
twenty-four  pounds  each,  according  to  the  specific  gravity  of  the 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  209 

stone  employed,  and  about  twenty-six  blocks  are  required  per 
square  yard.  The  dimensions  of  blocks  from  different  factories 
vary  slightly. 

The  blocks  are  laid  on  the  street  in  close  contact,  in  the  same 
manner  as  stone  paving-blocks,  either  with  or  without  an  artificial 
foundation;  the  foundation  usually  employed  is  gravel  or  gravel  and 
sand  or  sand  alone. 

293.  Advantages   and   Defects. — The    advantages  and    defects 
stated  under  Asphalt  Pavement  in  Articles  221  and  222  are  equally 
applicable  to  asphalt  block   pavements.      The   special   advantage 
which  they  possess  over  "  Sheet "  asphalt  is  that  they  can  be  made 
at  a  factory  located  near  the  materials,  whence  they  can  be  trans- 
ported to  the  place  where  they  are  to  be  used,  and  laid  by  ordinary 
pavers  without  the  aid  of  skilled  labor  ;  whereas  sheet  pavements 
require  special  machinery  and  skilled  labor  in  each  city  where  they 
iire  laid. 

Compared  with  stone  blocks  they  are  much  smoother  and  less 
noisy,  and  they  form  a  practically  impervious  pavement,  because 
tinder  the  action  of  the  sun  and  traffic  the  asphalt  cements  the 
blocks  together. 

For  narrow  well-travelled  streets  they  do  not  make  a  suitable 
pavement,  but  where  the  traffic  is  of  such  a  character  (such  as  resi- 
dence streets  where  the  traffic  is  light)  to  warrant  their  use  they 
make  when  laid  upon  a  concrete  foundation  an  excellent  pavement, 
smooth,  durable,  and  easily  cleaned,  healthy  and  pleasant  to  the 
eye. 

294.  Cost.— The  blocks  cost  abouc  $60.00  per  1000  or  $1.56  per 
square  yard  f.  o.  b.  at  the  factory. 

The  cost  of  construction  will  vary  with  the  locality,  cost  of 
transportation,  character  of  foundation,  etc.  Table  XXXVI  shows 
the  extent  and  cost  of  construction  in  some  of  the  principal  cities  in 
1890. 

In  Washington,  D.  0.,  the  contract  price  for  1900  was  $1.77  per 
square  yard. 


210 


HIGHWAY    CONSTRUCTION. 


TABLE  XXXVI. 

EXTENT  AND  COST  OP  ASPHALT-BLOCK    PAVEMENTS  IN  SOME  OF  THE 
PRINCIPAL  CITIES  OP  THE  UNITED  STATES  IN  1890. 


Cities. 

Extent. 
Miles. 

Cost  of  Construction 
per  square  yard. 

Philadelphia  Pa  

1880 

Washington,  D.  C  

10  10 

$2  00 

Camden    N  J                 ... 

5  86 

o  f)() 

Chicago    111  

4  11 

2  00 

Trenton,  N.  J.  .  .  

2  50 

2  50 

Schenectady,  N.  Y  

0  75 

295.  Cost  of  Maintenance. — No  statistics  are  available  as  to  the 
cost  of  maintenance.    Some  of  the  cities  using  them  report  that  no 
repairs  have  been  made  in  five  years,  and  that,  as  the  traffic  is  very 
light,  it  does  not  appear  likely  that  repairs  will  have  to  be  made; 
others  report  that  no  repairs  have  been  made  and  that  the  blocks 
are  badly  worn.     (See  also  Art.  782,  et  seq.)* 

296.  Specifications    for    Laying    Compressed-asphalt   Blocks.— 
Upon  the  soil-bed,  previously  compacted  by  rolling  and  ramming,, 
a  layer  of  bank  gravel,  screened  from  all  pebbles  measuring  more 
than  one  and  one-half  (1J)  inches  in  their  largest  dimensions,  will 
be  laid  of  such  depth  as  to  give  five  (5)  inches  in  thickness  when 
compacted  by  rolling  and  ramming.      Upon  the   gravel  will  be 
spread  a  layer  of  fine  sharp  sand  two  (2)  inches  in  thickness,  to 
serve  as  a  bed  for  the  blocks,  which  will  be  laid  directly  upon  and 
embedded  in  it  with  close  joints.     Special  care  will  be  observed  to 
make  the  surface  of  the  sand  exactly  parallel  to  the  surface  of  the 
pavement    when    completed.     The  blocks  shall   be   laid   by   the 
pavers  standing  or  kneeling  upon  the  blocks  already  laid,  and  not 
upon  the  bed  of  sand. 

The  blocks  shall  be  laid  with  their  length  at  right  angles  to  the 
axis  of  the  street;  each  course  will  be  formed  with  blocks  of  a  uni- 
form width  and  depth.  The  blocks  shall  be  so  laid  that  all  longi- 
tudinal joints  shall  be  broken  by  a  lap  of  at  least  four  (4)  inches. 

*  Cost  of  maintaining  asphalt-block  pavements,  Baltimore,  Md.,  1897  : 

Cost  per  square  yard  :  Highest $0.1633 

Lowest 0.0013 

Average 0.0711 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  211 

Each  course  of  blocks  will  be  driven  against  the  course  preceding 
it  by  a  heavy  wooden  maul,  in  order  to  make  the  lateral  joints  as 
tight  as  possible.  The  longitudinal  joints  will  be  closed  by  pressing 
on  a  lever  inserted  at  the  end  of  the  course  adjoining  the  curb,  and 
keying  with  a  block  cut  to  the  required  size.  When  laid,  the 
blocks  will  be  immediately  c@vered  with  clean,  fine  sand  entirely 
free  from  loam  or  earthy  matter,  perfectly  dry,  and  screened 
through  a  screen  having  20  meshes  to  the  inch.  The  blocks  will 
then  be  rammed  by  placing  an  iron  plate,  24  inches  by  8  inches, 
and  |  inch  thick,  over  four  blocks,  and  striking  on  the  plate  with  a 
rammer  weighing  not  less  than  45  Ibs.  The  ramming  will  be  con- 
tinued until  the  blocks  reach  a  firm,  unyielding  bed  and  present  a 
uniform  surface,  with  the  required  grade  and  crown.  Any  lack  of 
uniformity  in  the  surface  must  be  corrected  by  taking  up  the 
blocks,  increasing  the  sand  bedding,  and  relaying  them.  When  the 
ramming  is  completed,  a  sufficient  amount  of  fine,  dry  sand,  as 
above  described,  will  be  spread  over  the  surface  and  swept  into  the 
joints. 

297.  American    Bituminous-rock    Pavements. — Beds    of    sand- 
stone rock  impregnated  with  bitumen  are  found  in  many  places 
in  the  United  States,  but  it  is  only  within  the  last  few  years 
that  it  has  come  into  use  as  a  paving  material.     San  Francisco, 
Los  Angeles,  and  other  cities  now  have  several  miles  of  this  pave- 
ment. 

298.  The  rock  is  quarried,  broken  into  fragments,  heated,  and 
while  hot  taken  to  the   street  and   compressed  by  rolling  and 
tamping. 

299.  The  reports  concerning  the  durability  of  these  pavements 
are  conflicting.     A  claim  is   made   that   pavements   made  of  this 
material  15  years  ago  and  used  under  heavy  traffic  have  recently 
been  removed  and  found  to  have  lost  very  little  either  in  weight 
or  thickness.     On  the  other  hand,  it  is  claimed  that  these  pave- 
ments  are   soft;    that  wheels   and   horses   sink   into   them   quite 
deeply,  but  these  marks  appear  to  be  more  or  less  obliterated  by 
the  next  passing  vehicle. 

The  granular  nature  of  these  pavements  renders  them  less 
slippery  than  the  ordinary  asphalt  pavements.  They  also  possess 
the  quality  of  resisting  disintegration  by  moisture.  It  is  also 
claimed  that  these  pavements  stand  equally  well  the  high  tern- 


212  HIGHWAY    CONSTRUCTION. 

perature  of  the  interior   cities  and  the  cold,  damp  atmosphere  of 
the  coast. 

300.  Cost  of  Construction. — The  cost  of   construction   in   the 
West  is  less  than  that  of  the  standard  asphalt,  the  average  being 
ftbout  $2.50  per  square  yard,  including  a  6-inch  concrete  base,     In 
the  Eastern  cities  there  is  but  little  difference  in  their  cost. 

301.  Cost  of  Maintenance. — As  none  of  these  pavements  has  been 
laid  on  a  large  scale  for  a  sufficient  length  of  time,  nothing  can  be 
said  as  to  the  cost  of  maintaining  them. 

302.  One  ton  of  the  bituminous  rock  will  form  10  square  yards 
of  pavement  2  inches  thick. 

303.  Specifications  for  Bituminous-rock  Pavements. — The  man- 
ner of  laying  the  bituminous  rock  is  left  to  the  contractor,  except 
in  the  following  particulars : 

The  bituminous  rock  used  for  the  paving  must  contain  not  less 
than  7  nor  more  than  13  per  cent  of  its  weight  of  bitumen. 

The  powdered  rock  shall  be  prepared  at  a  uniform  temperature 
in  suitable  boilers. 

Ten  days  before  the  award  of  contracts  bidders  must  deposit  in 
the  office  of  the  engineer  samples  of  the  bituminous  rock  which 
they  propose  to  use.  Each  sample  shall  bear  the  bidder's  name 
and  the  name  of  the  place  where  obtained.  All  materials  used 
must  conform  to  the  samples  so  deposited.  If  other  material  is 
wished  to  be  used,  samples  of  them  must  be  deposited  and  accepted 
by  the  engineer. 

The  asphalt  covering,  when  completed,  is  to  have  a  thickness 
of  at  least  2  inches,  everywhere  equally  firm  and  compact,  and 
jointing  closely  to  the  curb  of  the  sidewalks,  gutter-covers,  etc., 
and  the  surface  must  in  every  place  conform  to  the  prescribed 
longitudinal  transverse  profiles. 

Laying  the  Asphalt. — The  asphalt  is  to  be  laid  in  dry  weather. 
Work  must  not  be  carried  on  during  rains  or  snowstorms.  Only 
on  the  special  permission  of  the  engineer  may  the  asphalt  be  laid 
on  the  concrete,  which  is  to  be  thoroughly  cleaned  of  earth,  dirt, 
and  loose  substances  of  all  kinds.  If  the  cleaning  reveals  any  soft 
or  injured  places  in  the  concrete,  they  are  to  be  chiselled  out  and 
filled  with  new  concrete  containing  a  greater  proportion  of  cement. 
This  is  not  to  be  covered  over  until  it  has  set. 

All  possible  measures  must  bo  taken  to  prevent  the  cooling 
of  the  asphalt  powder  while  being  carried  to  the  place  where  it  is 


ASPHALTUM    AND    COAL-TAR    PAYEMENTS.  213 


to  be  laid.  While  the  hot  powder  is  being  spread  out  and  before 
the  commencement  of  the  tamping  and  rolling,  the  greatest  care 
must  be  exercised  in  removing  all,  even  the  smallest,  foreign 
bodies,  such  as  stones,  paper,  wood,  straw,  leaves,  cigar-stumps, 
etc.,  and  no  one  shall  be  allowed  to  throw  such  bodies  on  the 
work.  Moreover,  the  carts  in  which  the  asphalt  is  to  be  moved! 
must  be  carefully  cleaned  after  each  use.  The  engineer  has  the 
right  to  require  proofs  of  their  cleanliness,  and  to  require  a  second 
cleaning  under  supervision. 

303a.  Expansion  of  Asphalt. — The  coefficient  of  expansion  of 
asphalt  paving  material  has  not  been  definitely  determined,  but 
the  investigations  made  so  far  indicate  that  it  has  about  the  same- 
coefficient  as  steel,  which,  according  to  Kent,  is  .0000063811. 

303b.  Repairs  to  Asphalt  Pavements.— The  damages  which 
have  usually  to  be  repaired  in  the  surface  of  an  asphalt  pavement 
are  :  cracks,  rolls  or  waves,  and  disintegration,  breaking  down  or 
wearing  away  in  patches. 

Irregular  Cracks.— These  are  generally  attributed  to  contrac- 
tion of  the  asphalt  from  cold;  in  some  cases  they  are  due  to  the 
settlement  and  cracking  of  the  foundation.  They  usually  start 
near  the  gutter,  and  gradually  extend  in  an  irregular  course  across 
the  street.  They  are  also  found  radiating  from  manhole-heads  and 
other  street  furniture  set  in  the  pavement,  and  sometimes  at  the 
junction  of  a  new  with  an  old  pavement,  and  at  the  joint  between 
one  day's  work  and  another.  They  appear  sooner  and  increase 
more  rapidly  on  a  street  with  little  traffic.  (With  respect  to  this- 
peculiarity,  Mr.  A.  W.  Dow,  Inspector  of  Asphalts  and  Cements,. 
Washington,  D.  0.,  says  :  "This  appears  on  first  thought  para- 
doxical, but  it  is  simply  explained.  When  the  pavement  is  sub- 
jected to  a  continuous  traffic,  the  asphalt  surface,  which  is  more 
or  less  plastic  at  all  temperatures,  is  kept  from  cracking  by  the 
constant  kneading,  so  to  speak,  produced  by  the  traffic.  And 
again,  when  an  asphalt  surface  has  but  little  or  no  traffic,  it  be- 
comes more  porous,  owing  to  the  fact  that,  expanding  and  contract- 
ing from  heat  and  cold  without  the  compression  due  to  traffic,  it 
becomes  spongy  and,  as  a  consequence,  materially  weakened.  If 
such  cracking  occurs  at  all  on  a  street  with  a  fair  amount  of 
traffic,  it  is  evident  that  the  paving  mixture  used  is  at  fault,  either 


214  HIGHWAY   CONSTRUCTION. 

in  not  being  rich  enough  in  oitumen,  or  the  asphalt  cement  used 
was  too  hard.") 

In  order  to  lessen  the  tendency  to  crack,  and,  if  possible,  con- 
fine it  within  certain  limits,  expansion-joints  have  been  used  in 
several  places.  City  Engineer  Thompson  of  Peoria,  111.,  has  pro- 
vided expansion  spaces  at  intervals  of  50  feet.  These  were  made 
by  cutting  the  asphalt  surface  (after  it  had  been  compacted  with  a 
hand-roller),  with  an  ordinary  trowel,  down  to  the  concrete  ;  the 
crevice  thus  formed  was  filled  with  dry  cement,  and  the  compac- 
tion continued  with  a  steam-roller. 

The  employment  of  expansion- joints  seems  to  be  of  doubtful 
utility.  The  asphalt  mixture  being  more  or  less  plastic,  the  space 
will  be  closed  under  the  action  of  the  traffic.  If  the  mixture  be 
sufficiently  hard  to  resist  the  spreading  action  of  the  traffic,  and 
thus  keep  the  joint  open,  its  edges  will  be  broken  down  and  the 
pavement  will  be  speedily  disintegrated;  they  also  afford  an  en- 
trance to  water,  which,  finding  its  way  under  the  surface  material, 
will  quickly  rot  it;  hence  they  are  equally  objectionable  as  the 
cracks  which  they  are  intended  to  avoid.  The  tendency  to  crack 
may  be  lessened,  and  in  many  cases  eliminated,  by  the  use  of  a  ce- 
ment as  soft  as  is  practicable  to  put  into  the  mixture  without  having 
it  mark  too  badly  in  the  hottest  weather  to  which  the  ''pavement 
will  be  subjected. 

Cracks  are  repaired  by  first  cleaning  thoroughly,  then  filling, 
by  pouring  in  asphaltic  cement. 

Rolls  or  Waves.— This  condition  may  be  produced  by  (a)  un- 
equal thickness  ;  (b)  sliding  towards  the  gutter  under  the  action  of 
the  traffic  ;'  (c)  creeping  in  the  direction  of  the  heaviest  traffic;  (d) 
expansion  of  the  asphalt  or  the  concrete  or  both ;  (e)  too  soft  a  ce- 
ment; (/)  a  defective  bond  between  the  base  and  binder  (this 
occurs  when  the  surface  of  the  concrete  is  made  smooth  by  bring- 
ing an  excess  of  mortar  to  the  surface  through  too  much  ramming, 
or  by  the  use  of  an  inappropriate  aggregate)  ;  (g)  a  defective  bond 
between  the  binder  and  the  wearing  surface  (a  proper  union  is 
prevented  between  binder  and  wearing  surface  when  the  binder 
contains  an  excess  of  cement,  or  its  surface  is  dirty  when  the  wear- 
ing coat  is  put  on) ;  (h)  a  combination  of  two  or  more  of  the  fore- 
going. 


ASPHALTUM   AND   COAL-TAR   PAVEMENTS.  215 

The  above  causes  are  due  to  errors  in  the  preparation  of  the 
different  parts  of  the  pavement,  or  defects  in  its  laying,  and  their 
occurrence  may  be  prevented  by  the  exercise  of  proper  care. 

Disintegration. — This  usually  occurs  in  spots,  and  may  be  pro- 
duced by  any  one  or  a  combination  of  the  following  causes :  (a)  ex- 
cessive traffic;  (b)  action  of  water;  (c)  unsuitable  asphalt;  (d)  un- 
suitable flux;  (e)  Imperfect  mixture  and  improper  manipulation; 
(f)  deficiency  of  asphalt  cement;  (g)  soft  spots  due  to  an  excess  of 
cement;  (h)  improper  binder;  (i)  action  of  illuminating-gas. 
The  damage  due  to  disintegration  is  repaired  by  cutting  out  the 
surface  material  down  to  the  base  and  replacing  with  new  material. 

The  repairing  of  an  asphalt  surface  is  now  generally  effected  by 
the  "skimming  process/7  in  which  is  used  either  a  heater,  such  as 
the  "  Perkins  "  (Fig.  267),  having  a  tank  for  fuel-oil  and  hooded 
burners,  or  an  open  grate  on  low  wheels,  in  which  coke  is  burned. 
Either  of  these  appliances  is  placed  immediately  over  that  part  of 
the  pavement  to  be  repaired,  and  sufficient  heat  is  produced  to 
soften  the  asphalt  so  that  it  can  be  scraped  off  to  the  required 
depth.  To  protect  the  adjoining  pavement  from  injury,  the  por- 
tion to  be  removed  is  surrounded  with  asbestos  boards. 

It  is  claimed  that  by  the  "  skimming  process  "  a  perfect  union 
can  be  secured  between  the  new  material  and  the  old  pavement. 
It  is  not  advisable  to  take  this  statement  as  an  established  fact.  In 
many  cases  the  patches  have  scaled  or  peeled  off.  This  may  have 
been  due  to  careless  manipulation,  presence  of  moisture,  or  de- 
fective material. 

The  injury  to  gutters  is  usually  repaired  by  cutting  out  and 
replacing  the  surface  material  and  by  painting  with  liquid  cement. 

303c.  Specifications  for  the  Repairs  of  Asphalt  Pavements. 

Extent  of  Repairs. — The  repair  of  wearing  surface,  binder,  and 
concrete  base  shall  be  made  to  such  an  extent  as  is  directed  by 
the  city  engineer. 

In  every  case  the  defects,  such  as  ruts,  cracks,  depressions, 
holes,  etc.,  are  to  be  remedied  and  repaired.  Pavement  taken  up  to 
give  access  to  sewer-,  water-,  gas-,  or  other  underground  pipes  or 
structures  will  be  included  under  the  head  of  repairs. 

Concrete  Base.—When  it  is  necessary  to  replace  the  concrete 
base,  the  base  thus  replaced  shall  be  six  (6)  inches  in  thickness, 


210  HIGHWAY   CONST  RUCTION. 

and  composed  of  one  part  of  freshly  burned  hydraulic  (KoSf) 
cement  and  two  parts  of  clean,  sharp,  coarse  sand,  and  five  parts 
of  clean  broken  stone,  all  by  measure. 

The  material  from  the  old  concrete  shall  not  be  used  in  restor- 
ing the  base. 

Earth  Foundation. — Should  the  earth  under  the  concrete  to 
be  replaced  be  soft,  spongy,  or  otherwise  deficient  in  affording  a 
firm  foundation,  it  shall  be  dug  out  and  replaced  with  sand, 
gravel,  or  broken  stone  well  compacted  by  ramming. 

Binder. — The  binder  course  will  be  placed  on  the  concrete  base, 
and  shall  consist  of  a  concrete  made  of  clean  broken  stone  not  ex- 
ceeding one  and  one-half  (1J)  inches  in  the  largest  dimension,  and 
asphalt  paving-cement  (or  coal-tar  paving  composition  No.  4).  The 
stone  will  be  heated  to  the  required  temperature  in  revolving  heat- 
ers, and  shall  be  thoroughly  mixed  by  machinery  with  the  cement  in 
the  proportion  of  one  gallon  of  cement  to  one  cubic  foot  of  stone. 
The  binder  will  be  hauled  to  the  work  while  hot,  carefully  spread 
on  the  base  with  hot  iron  rakes  to  such  a  depth  that  the  least 
thickness  for  the  wearing  surface  will  be  1J  inches  when  the  sum 
of  the  wearing  surface  and  binder  is  not  over  2  inches.  As  ihis 
sum  increases  the  thickness  of  the  wearing  surface  will  be  increased 
until  it  attains  a  depth  of  2  inches.  Beyond  this  the  thickness 
of  the  binder  may  be  increased  when  the  wearing  surface  has  slid 
on  the  concrete.  The  surface  of  the  latter  must  be  roughened  by 
picks. 

Wearing  Surface. — Upon  the  binder  the  wearing  surface  shall 
be  laid.  This  shall  consist  of  the  same  kind  of  composition  or 
kind  of  asphalt  as  the  existing  pavement,  and  laid  so  as  to  bring 
the  surface  even  with  the  adjoining  pavement,  making  a  close, 
smooth  joint  therewith,  without  any  cracks,  depressions,  or  eleva- 
tions. The  edges  of  the  old  pavement  shall  be  cut  so  as  to  form 
a  bevelled  joint,  and  will  be  painted  with  hot  asphaltum  before 
the  new  material  is  laid. 

The  repairs  are  to  be  so  made  that  at  the  completion  of  each 
day's  work  no  holes  cut  out  for  repair  shall  be  left  unfilled  or  un- 
finished. The  holes  must  be  perfectly  dry  before  the  material  is 
laid,  and  no  material  shall  be  laid  during  a  rain. 

Old  Material — All  old  material,  dirt,  asphalt,  concrete,  etc., 


ASPHALTUM    AND    COAL-TAR    PAVEMENTS.  217 

broken  up  is  to  be  the  property  of  the  contractor,  and  must  be 
removed  promptly  from  the  street  by  him. 

303d.  Specifications  for  the  Condition  of  Asphalt  Pavements  at 
End  of  Guarantee  Period. — 1.  The  pavement  shall  not  be  reduced 
more  than  one-fourth  (^)  inch  from  the  original  thickness  at  the 
end  of  the  first  five  years,  nor  more  than  one-half  (J)  inch  from 
the  original  thickness  at  the  end  of  the  first  ten  years.  (This  re- 
quirement shall  not  apply  to  pavements  constructed  of  rock  as- 
phalt, as  this  material  does  not  receive  its  ultimate  compression  for 
a  considerable  period  after  being  laid.) 

2.  Places  which  show  a  disintegration  of  the  material  shall  be 
removed  to  the  binder  or  concrete  foundation,  as  found  necessary, 
and  replaced  with  new   material  having  the  same  thickness  and 
conforming  to  the  adjacent  pavement. 

3.  All  elevations  or  depressions  three-eighths  (J)  of  an  inch  or 
more  above  or  below  the  general  surface  of  the  street  shall  be 
brought  to  the  same  elevation  as  the  general  surface,  these  eleva- 
tions  and   depressions    to   be   determined   by  measuring   from    a 
straight-edge  four  (4)  feet  in  length,  placed  on  the  surface  of  the 
pavement  parallel  to  the  line  of  curbing.     (In  making  such  repairs 
the  process  known  as  "skimming"  may  be  employed.) 

4.  Where  elevations  or  depressions  are  due  to  the  failure  of  the 
concrete  foundation  from  any  cause,  the  asphalt  and  concrete  shall 
both  be  removed  a  length  and  width  to  include  the  entire  defect. 
If  the  failure  is  due  to  buckling  of  the  concrete,  the  new  founda- 
tion shall  consist  of  broken  stone  thoroughly  compacted,  and  of 
the  same  thickness  as  the  original  concrete.     In  all  other  cases  a 
new  foundation  of  concrete  shall  be  placed  of  the  same  quality  and 
thickness  as  the  original  construction.     Upon  the  foundation  shall 
be  placed  the  pavement,  of  the  same  thickness  as  the  adjacent  sur- 
faces. 

5.  Cracks   which    show   any   indication   of   disintegration,   or 
which  are  three-eighths  (f)  of  an  inch  or  more  in  width,  shall  be 
cut  out  to  the  binder  or  concrete  foundation,  as  found  necessary,  a 
length  and  width  sufficient  to  include  the  entire  portion  affected  : 
this  portion  to  be  replaced  with  new  material  of  the  same  quality 
and  thickness  as  shown  in  the  pavement  adjacent  thereto. 

6.  Should  it  be  found  necessary  to  replace  twenty-five  per  cent 


218  HIGHWAY   CONSTRUCTION. 

or  more  of  any  section  of  the  street  with  new  material,  the  entire 
section  shall  be  resurfaced. 

The  above  specifications  are  recommended  by  the  Committee 
on  Street  Paving  of  the  American  Society  of  Municipal  Improve- 
ments, with  the  following  comment : 

"  Your  committee  does  not  consider  it  possible  to  give  definite 
specifications  for  this  work  that  will  be  applicable  to  all  localities, 
but  after  a  careful  consideration  of  all  the  facts  obtainable,  and 
after  due  consideration  of  the  opinions  presented,  we  would  recom- 
mend that  the  following  [above]  clauses,  modified  as  found  neces- 
sary for  each  locality,  be  included  in  the  guarantee  contracts  of  the 
cities  belonging  to  the  association." 


CHAPTER  VI. 
BRICK  PAVEMENTS. 

304.  BRICK,  although   one   of  the  oldest   materials   used  for 
paving,  was  not  employed  for  this  purpose  in  the  United  States 
until  about  twenty  years  ago.     The  first  brick  pavement  laid  in  the 
United  States  was  in  Charleston,  W.  Va.,  in  1872.     Since  then  the 
use  of  brick  as  a  paving  material  has  extended  over  a  wide  section 
of  country;  and  in  localities  with  moderate  traffic  such  pavements 
appear  to  give  satisfaction. 

305.  The  advantages  of  brick  pavements  may  be  stated  as  fol- 
lows: 

(1)  Ease  of  traction. 

(2)  Good  foothold  for  horses. 

(3)  Not  disagreeably  noisy. 

(4)  Yields  but  little  dust  and  mud. 

(5)  Adapted  to  all  grades. 
{6)  Easily  repaired. 

(7)  Easily  cleaned. 

(8)  But  slightly  absorbent. 

(9)  Pleasing  to  the  eye. 

(10)  Expeditiously  laid. 

(11)  Durable  under  moderate  traffic. 

Brick  pavements  will  be  found  in  many  localities  to  be  superior 
to  wood  or  broken  stone,  and  in  many  cities  and  towns  will  be 
found  superior  to  stone  blocks. 

306.  The  Defects  of  Brick  Pavements.— The  principal  defects  of 
brick  pavements  arise  from  lack  of  uniformity  in  the  quality  of  the 
bricks  and  the  liability  of  incorporating  in  the  pavement  bricks  of 
too  soft  or  porous  structure,  which  crumble  under  the  action  of 
traffic  or  frost. 

The  employment  of  unsuitable  brick  is  liable  to  be  fostered  by 
a  popular  desire  to  help  a  local  industry  without  due  regard  to  the 

219 


220 


HIGHWAY    CONSTRUCTION. 


TYPES    OF   BRICK   PAVEMENTS. 


FIG.  1  6.— SECTION  OF  HALE  PAVEMENT. 


FIG,  17,— PLAN  OF  HALE  PAVEMENT, 


&^ 
FIG.  18.-SECTION  OF  BRICK  PAVEMENT  ON  CONCRETE. 


I      '      I    ~1 I 


I      I      I    =1 


i      i    rn  .1    .  i 


c:  =n  n=  n  .    i   .    • 


i       i       i 


FIG.  19.— PLAN  SHOWING  ARRANGEMENT  OF  JUNCTION, 


BRICK    PAVEMENTS.  221 


quality  of  the  local  clays  for  the  manufacture  of  good  paving  brick. 
This  circumstance,  together  with  the  comparative  ease  with  which 
contractors  who  have  little  experience  can  bid  on  this  class  of  work, 
and  the  difficulty  of  rejecting  the  lowest  bid  by  local  authorities, 
will  in  many  places  result  in  the  failure  of  the  brick  pavements,, 
Jf  cities,  however,  in  making  contracts  for  brick  pavements,  will 
keep  these  contingencies  in  mind,  and  as  far  as  possible  exercise 
discrimination  in  selecting  bricks  made  especially  for  this  purpose 
and  contractors  interested  in  making  these  pavements  popular, 
then  the  development  of  a  great  industry  may  be  anticipated. 

307.  Durability. — Brick  has  been  used  for  upwards  of  a  hun- 
dred years  in  the  Netherlands,  and  pavements  laid  half  a  century 
ago  are  still  in  good  condition.     There  are  several  brick  pavements 
in  the  United  States  from  ten  to  eighteen  years  old  which  are 
still  in  good  condition. 

308.  The  general  experience  with  pavements  formed  of  suitable 
brick,  laid  on  an  unyielding  foundation,  with  the  joints  filled  with 
bituminous  or  Portland-cement  grout,  is  that  they  furnish  a  smooth 
and  durable  surface,  well  adapted  to  moderate  traffic. 

309.  Failures  of  the  earlier  pavements  are  frequently  reported. 
These  pavements  were  generally  constructed  on  defective  founda- 
tions, and  with  the  ordinary  building  bricks  of  the  locality.     Such 
failures  are  the  result  of  overhaste  in  the  selection  of  the  material, 
and  poor  foundations. 

310.  The  durability  of  the  bricks  seems  to  depend  (1)  on  the 
clay  from  which  they  are  made  being  practically  free  from  lime; 
(2)  on  the  thorough  grinding  and  mixing  of  the  clay,  so  as  to  have 
no  lumps  in  the  bricks;  (3)  upon  the  bricks  being  thoroughly  an- 
nealed. 

311.  The  brick  pavements  at  The  Hague,  Holland,  are  made  of 
a  hard-burned  brick   8.668  inches  by  4.33  inches  wide  and  2.16 
inches  thick.     They  are  laid  on  a  sand  foundation  7.88  inches  deep, 
with  very  little  clay.     Joints  are  laid  as  close  as  possible. 

The  Hague  is  a  city  of  residences,  and  street  traffic  is  very  light. 
Amsterdam  is  paved  almost  entirely  with  brick.  The  road  from 
Utrecht  to  Connighem,  twenty-seven  miles,  is  paved  with  brick. 

312.  Bricks  are  successfully  used  in  Rotterdam,  which  is  a  com- 
mercial city.     Two  classes  of  brick  are  used — one  made  from  local 
clays,  anji  the  other  a  scoria  brick,  manufactured  by  the  Tees  Scoria 


222  HIGHWAY    CONSTRUCTION. 

Brick  Company,  of  England.     The  local  bricks  are  preferred  for 
light  traffic,  and  for  medium  traffic  the  scoria  bricks. 

313.  Size  and  Shape  of  Bricks. — Bricks  are  passing  through  an 
ordeal 'Similar  to  that  through  which  wood  for  paving  passed  many 
years  ago,  with  practically  the  same  results,  viz.,  that  with  a  proper 
foundation  neither  odd  shapes,  grooves,  lugs,  nor  other  devices  are 
necessary  or  beneficial.     Experience  shows  that  the  most  economi- 
cal and  desirable  size  for  paving  bricks  is  that  of  the  standard 
building  brick.     Bricks  of  this  size  can  be  made  more  cheaply,, 
burned  more  uniformly,  and  those  which  are  unsuitable  for  paving; 
can  be  utilized  for  building  purposes,  which  would  be  impracticable 
with  odd  shapes.     The  imperfect  ones  of  said  shapes  or  peculiar 
form  are  so  much  waste  material,  and  the  cost  of  their  manufacture 
must  be  added  to  the  price  of  the  good  ones  in  order  to  protect  th(i 
manufacturer  from  loss.     Moreover,  with  irregular  sizes  and  odd 
shapes  it  would  be  necessary  for  the  towns  employing  brick  pave- 
ments to  keep  a  large  stock  of  the  different  bricks  on  hand  to  make- 
repairs,  which  would  be  expensive  and  troublesome.* 

314.  duality  of    Bricks. — The   qualities    essential   to   a    good 
paving  brick  are  the  same  as  for  any  other  paving  material,  viz., 
hardness,  toughness,  and  ability  to  resist  the  disintegrating  effects 
of  water  and  frost.     As  with  other  materials,  porous  brick  are  unfit 
for  paving. 

These  qualities  are  not  obtained,  as  is  commonly  supposed,  by 
vitrifying  the  bricks :  in  fact  the  application  of  the  term  vitrified  to 
paving  bricks  is  a  misnomer.  The  process  of  vitrification  is  to  con- 
vert into  glass  by  fusion  or  the  action  of  heat.  Glass  is  a  smooth, 
impermeable,  brittle  substance,  easily  fractured ;  therefore  the  edges 
of  bricks  that  are  vitrified  or  turned  into  glass  will  be  quickly 
broken  off,  and  their  surface  will  be  slippery.  Vitrification  adds 
nothing  to  the  strength ;  in  fact  it  defeats  the  object  for  which  the 
bricks  are  made. 

315.  The  required  qualities  are  imparted  to  the  brick  by  a  pro- 
cess of  annealing.     The  bricks  should  be  burned  just  to  the  point 
of  fusion,  then  the  heat  gradually  reduced  until  the  kiln  is  cold. 
This  process  will  produce  a  brick  thoroughly  compact,  hard,  and 

*  Cleveland,  Philadelphia,  and  other  cities  require  that  the  bricks  shall 
have  projections  of  £  inch  on  the  vertical  sides,  to  insure  open  joints  for  re- 
ceiving the  filling  material.  • 


BRICK    PAVEMENTS.  223 


tough.     If  the  cooling  off  is  done  quickly,  it  will  produce  a  brittle 
brick,  that  will  speedily  go  to  pieces  under  traffic. 

316.  Foundation.— A  solid  unyielding  foundation  is  as  indis- 
pensable with  bricks  as  with  any  other  paving  material  :  the  fail- 
ure of  the  earlier  pavements  was  due,  in  many  cases,  more  to  de- 
fective foundations  than  to  defective  material.     The  use  of  plank 
laid  on  sand  is  objectionable  for  the  same  reasons  stated  under 
wood  pavements,  Articles  185,  186. 

317.  The  foundation  in  all  cases  should  be  formed  of  cement 
concrete,  the  aggregate    of   which,  in   localities   where   stone   or 
gravel  are  unobtainable,  may  be  of  broken  bricks. 

The  usual  proportions  for  the  concrete  are  :  hydraulic  cement 
1  part,  clean,  sharp  sand  2  parts,  broken  stone  5  parts. 

317a.  Sand  Cushion. — The  sand  cushion  is  a  layer  of  sand 
placed  on  top  of  the  concrete  to  form  a  bed  for  the  brick.  Prac- 
tice regarding  the  depth  of  this  layer  of  sand  varies  considerably. 
In  some  cases  it  is  only  half  an  inch  deep,  varying  from  this  up  to 
three  inches.  The  sand  cushion  is  very  desirable,  as  it  not  only 
forms  a  perfectly  true  and  even  surface  upon  which  to  place  the 
brick,  but  it  also  makes  the  pavement  less  hard  and  rigid  than 
would  be  the  case  were  the  brick  laid  directly  on  the  concrete. 

The  sand  is  spread  evenly,  sprinkled  with  water,  smoothed  and 
brought  to  the  proper  contour  by  screeds  or  wooden  templets,  prop- 
erly trussed,  mounted  on  wheels  or  shoes  which  bear  upon  the 
upper  surface  of  the  curb.  Moving  the  templet  forward  levels  and 
forms  the  sand  to  a  uniform  surface  and  proper  shape. 

The  sand  used  for  the  cushion-coat  should  be  clean  and  free 
from  loam,  moderately  coarse,  and  free  from  pebbles  exceeding 
one-quarter  inch  in  size. 

318.  Manner  of  Laying.— The  bricks  should  be  laid  on  edge,  as 
closely  and  compactly  as  possible,  in  straight  courses  across  the 
street,  with  the  length  of  the  bricks  at  right  angles  to  the  axis  of 
the  street.     Joints  should  be  broken  by  at  least  3  inches.     None 
but  whole  bricks  should  be  used   except  in  starting  a  course  or 
making  a  closure.     To  provide  for  the  expansion  of  the  pavement, 
both  longitudinal  and  transverse  expansion-joints  are  used;    the 
first  are  formed  by  placing  a  board  templet  seven-eighths  of  an 
inch  thick  against  the  curb  and  abutting  the  brick  thereto.     The 


HIGHWAY    CONSTRUCTION. 


transverse  joints  are  formed  at  intervals  varying  between  25  and 
50  feet,  by  placing  a  templet  or  building-lath  three-eighths  of  an 
inch  thick  between  two  or  .three  rows  of  brick.  After  the  bricks 
are  rammed  and  ready  for  grouting,  these  templets  are  removed, 
and  the  spaces  so  left  are  filled  with  coal-tar  pitch  or  asphaltic 
paving-cement.  The  amount  of  pitch  or  cement  required  will 
vary  between  one  and  one  and  a  half  pounds  per  square  yard  of 
pavement,  depending  upon  the  width  of  the  joints.  After  25  or 


FIG.  19A.— PLAN  OF  BRICK  PAVING  AT  STREET  INTERSECTIONS, 
30  feet  of  the  pavement  is  laid,  every  part  of  it  should  be  rammed 
with  a  rammer  weighing  not  less  than  50  pounds,  and  the  bricks 
which  sink  below  the  general  level  should  be  removed  and  replaced 
by  a  brick  of  greater  depth.  After  the  ramming  and  rectification 
Portland-cement  grout  should  be  poured  into  the  joints  until  it 
appears  on  the  surface  ;  then  the  whole  surface  should  be  covered 
with  a  layer  of  dry  sand  one-half  inch  deep.  At  street-intersec- 


BKICK    PAVEMENTS.  225 


the  course  should  be  laid  meeting  at  an  angle,  as  shown  in 
Pig.  19  or  19ff,  so  that  the  courses  may  not  run  parallel  to  the  traffic. 

319.  Joint-filling. — The  character  of  the  material  used  in  filling 
the  joints  between  the  brick  has  considerable  influence  on  the  suc- 
cess and  durability  of  the  pavement.  Various  materials  have  been 
used,  as  sand,  coal-tar  pitch,  asphalt,  mixtures  of  coal-tar  and 
asphalt,  Portland  cement,  and  various  patented  fillers,  as  "  Murphy's 
grout/'  made  from  ground  slag  and  cement;  each  material  has  its 
advocates,  and  there  is  much  difference  of  opinion  as  to  which 
gives  the  best  results. 

The  office  of  a  filler  is  to  prevent  water  from  reaching  the 
foundation,  and  to  protect  the  edges  of  the  brick  from  spalling 
under  traffic.  In  order  to  meet  both  of  these  requirements  every 
joint  must  be  filled  to  the  top  and  remain  so,  wearing  down  with 
the  brick.  Sand  does  not  meet  these  requirements,  although  at 
first  making  a  good  filler,  being  inexpensive,  and  reducing  the 
liability  of  the  pavement  to  be  noisy;  it  soon  washes  out  and 
leaves  the  edges  of  the  brick  unprotected  and  consequently  much 
more  liable  to  be  chipped.  Coal-tar  and  the  mixtures  of  coal-tar 
and  asphalt  have  an  advantage  in  rendering  the  pavement  less 
noisy  and  in  cementing  together  any  breaks  that  may  occur  by 
upheavals  from  frost  or  other  causes;  but  unless  made  very  hard 
they  have  the  disadvantage  of  becoming  very  soft  in  hot  weather 
and  flowing  to  the  gutters  and  low  places  in  the  pavement,  there 
forming  a  black  and  unsightly  scale,  leaving  the  high  parts  unpro- 
tected. The  joints  thus  deprived  of  their  filling  become  the  recep- 
tacle of  water,  mud,  and  ice  in  turn,  and  the  edges  of  the  brick  are 
quickly  broken  down.  Some  of  these  mixtures  become  so  brittle 
in  winter  that  they  crack  and  fly  out  of  the  joints  under  the  action 
of  the  traffic. 

The  Murphy  grout  works  well  in  places,  being  fairly  hard  and 
elastic,  but  is  said  to  be  uneven  in  its  results. 

The  best  results  seem  to  be  obtained  by  using  a  high  grade  of 
Portland  cement  containing  the  smallest  amount  of  lime  in  its 
composition,  the  presence  of  the  lime  increasing  the  tendency  of 
the  filler  to  swell  with  age  and  the  absorption  of  moisture,  causing 
the  pavement  to  rise  or  lift  away  from  the  foundation,  and  so  pro- 
ducing the  roaring  or  rumbling  noise  so  frequently  complained  of. 


226  HIGHWAY   CONSTRUCTION-. 

The  Portland-cement  grout,  when  uniformly  mixed  and  carefully 
placed,  resists  the  impact  of  traffic  and  wears  well  with  the  brick. 
When  a  failure  occurs  the  repairs  can  be  quickly  made;  and  if  made- 
early,  the  pavement  will  be  restored  to  a  good  condition;  but  if  neg- 
lected, the  brick  soon  loosens  and  the  pavement  fails. 

The  Portland-cement  filler  is  prepared  by  mixing  two  parts  of 
cement  and  one  part  of  fine  sand  with  sufficient  water  to  make  a 
thin  grout.  The  most  convenient  arrangement  for  preparing  and 
distributing  the  grout  is  a  water-tight  wooden  box  carried  on  four 
wooden  wheels  about  12  inches  in  diameter.  The  box  may  be 
about  4  feet  wide,  7  feet  long,  and  12  inches  deep,  furnished  with 
a  gate  about  8  inches  wide  in  the  rear  end.  The  box  should  be 
mounted  on  the  wheels  with  an  inclination,  so  that  the  rear  end  is 
about  4  inches  lower  than  the  front  end. 

The  operation  of  placing  the  filler  is  as  follows:  The  cement 
and  sand  are  placed  in  the  box  and  sufficient  water  is  added  to  make 
a  thin  grout.  The  box  is  located  about  12  feet  from  the  gutter, 
the  end  gate  opened  and  about  2  cubic  feet  of  the  grout  allowed  to- 
flow  out  and  run  over  the  top  of  the  brick  (care  being  taken  to  stir 
the  grout  while  it  is  discharging).  If  the  brick  are  very  dry,  the 
entire  surface  of  the  pavement  should  be  thoroughly  wet  with  a, 
hose  before  applying  the  grout;  if  not,  the  absorption  of  the  water 
from  the  grout  by  the  bricks  will  prevent  adhesion  between  the 
bricks  and  the  cement  grout.  The  grout  is  swept  into  the  joints  by 
ordinary  bass  brooms.  After  about  100  feet  in  length  of  the  pave- 
ment has  been  covered,  the  box  is  returned  to  the  starting-point 
and  the  operation  is  repeated  with  a  grout  somewhat  thicker  than 
the  first.  If  this  second  application  is  not  sufficient  to  fill  the 
joints,  the  operation  is  repeated  as  often  as  may  be  necessary  to  fill 
them.  If  the  grout  has  been  made  too  thin  or  the  grade  of  the 
street  is  so  great  that  the  grout  will  not  remain  long  enough  in 
place  to  set,  dry  cement  may  be  sprinkled  over  the  joints  and 
swept  in.  After  the  joints  are  completely  filled  and  inspected, 
allowing  three  or  four  hours  to  intervene,  the  completed  pavement 
should  be  covered  with  sand  to  a  depth  of  about  |  inch  and  the 
roadway  barricaded  and  no  traffic  allowed  on  it  for  at  least 
ten  days. 

If  coarse  sand  is  employed  in  the  grout,  it  will  separate  from 


BRICK    PAVEMENTS.  227 


the  cement  during  the  operation  of  filling  the  joints,  with  the 
result  that  many  joints  will  be  filled  with  sand  and  very  little 
cement,  while  others  will  be  filled  with  cement  and  little  or  no 
sand;  thus  there  will  be  many  spots  in  the  pavement  in  which  no 
bond  is  formed  between  the  bricks,  and  under  the  action  of  traffic 
these  portions  will  quickly  become  defective. 

The  object  of  covering  the  pavement  with  sand  is  to  prevent 
the  grout  from,  drying  or  setting  too  rapidly;  hence  in  dry  and 
windy  weather  it  should  be  sprinkled  from  time  to  time. 

The  coal-tar  filler  is  best  applied  by  pouring  the  material  from 
buckets  and  brooming  it  into  the  joints  with  wire  brooms.  To 
effectually  fill  the  joints  it  must  be  used  only  when  very  hot.  To 
secure  this  condition  a  heating-tank  on  wheels  is  necessary.  It 
should  have  a  capacity  of  at  least  five  barrels,  and  be  kept  at  a  uni- 
form temperature  all  day.  One  man  is  necessary  to  feed  the  fire 
and  draw  the  material  into  the  buckets,  another  to  carry  the  buck- 
ets from  the  heating-tank  to  a  third,  who  pours  the  material  over 
the  street.  The  latter  starts  to  pour  in  the  centre  of  the  street, 
working  backward  toward  the  curb,  and  pouring  a  strip  about  two 
feet  in  width.  A  fourth  man  with  a  wire  broom  follows  immedi- 
ately after  him,  sweeping  the  surplus  material  toward  the  pourer 
and  in  the  direction  of  the  curb.  This  method  leaves  the  entire 
surface  of  the  pavement  covered  with  a  thin  coating  of  the  pitch, 
which  should  be  immediately  covered  with  a  light  coating  of  sand; 
the  sand  becomes  imbedded  in  the  pitch.  Under  the  action  of  the 
traffic  this  thin  coating  is  quickly  worn  away,  leaving  the  surface 
of  the  bricks  clean  and  smooth. 

320.  Cost  of  Brick  Pavements. — The  cost  of  construction  of 
these  pavements  depends  largely  upon  the  facilities  for  obtaining 
the  requisite  material  and  the  character  of  the  foundation. 

The  cost  of  a  first-class  brick  pavement  per  square  yard  may  be 
estimated  as  follows: 


Excavation 

^tk  of  a  cubic  yard  of  concrete, 
Tyh  "       "         "      "  sand.... 

72  bricks  of  standard  size 

Labor  laying,  etc 

Freight 

2£  gallons  of  asphaltic  cement. , 


Total, 


228 


HIGHWAY    CONSTRUCTION". 


321.  Table  XXXVII  shows  the  cost  in  various  localities  in  the 
United  States. 

TABLE   XXXVII. 

EXTENT  AND  COST  OF  BRICK  PAVEMENT  IN  SEVERAL  LOCALITIES  IN  THE 
UNITED  STATES,  1898-99. 


Square  Yards. 

Cost  of  Construc- 
tion. 

Guaranty 
Period. 
Years. 

Akron  O        

252  267 

Albany  N   Y....  

228  777 

$1.79 

5,  7,  and  10 

260  591 

1.26 

5  160 

Altoona  Pa.  ...           

13  160 

1  60 

28  336 

1  85 

5  and  10 

Auburn,  N  Y  

30,000 

Baltimore   Md     .           

14  628 

2  50 

Bay  City  Mich       

36  243 

Bingbaraton   N  Y  

6  043 

5     1.72  ) 

5  and  10 

3926 

(     2.40  J 

Boston   Mass  

6  050 

Buffalo,  N  Y  

107  172 

j     1-37   ) 

Sand  10 

3  666 

(     2.40   f 
2  05 

260  480 

1.00 

1 

Cbattanooga   Tenn  

86  764 

44  000 

Chicago,  111  

330  000 

Cincinnati,  O  

432  200 

1  70 

Cleveland   O  

800  000 

1  12 

1  509  015 

j     1.25    ) 

11  600 

{     1.00    f 
1  10 

Dallas  Tex  

843 

467  684 

1  18 

Dayton,  O  

278  618 

5     1.87  ) 

5 

Des  Moiues,  Iowa  

1  509  195 

(     1.29  J 
1.40 

5 

Detroit,  Mich  

501  750 

1  25 

5 

113  568 

1  34 

Elinira,  N.  Y  

46,675 

j     2.17  ) 

5  and  7 

Erie  Pa  

119  796 

|     1.73  f 
1.50 

539  793 

1.51 

Fort  Wayne  Ind                  . 

133  566 

5 

Galveston,  Tex  

8,437 

Grand  Rapids,  Mich.  

62,075 

1.50 

Harrisbure,  Pa  

6,413 

Hartford,  Conn  

1,427 

BROKEN-STOXE    PAVEMENTS. 


229 


TABLE  XXXVII.— Continued. 

EXTENT  AND  COST  OP  BRICK  PAVEMENT  IN  SEVERAL  LOCALITIES  IN  THE 
UNITED  STATES,  1898-99. 


Square  Yards. 

Cost  of  Construc- 
tion. 

Guaranty 
Period. 
Years. 

31,933 

$2.04 

Houston   Tex                     •  .     ... 

133  430 

Indianapolis   Ind.  ...          

392,326 

j     1.50   ) 

9 

Jersey  City  N  J  

8,800 

(    2.00  y 

143,733 

Joliet    111  

77,775 

Kansas  City   Kans       

220,000 

502,247 

j     1.37  ) 

5  and  7 

96,000 

I     1.50  f 

Lancaster   Pa                   •    .  ..    . 

50,344 

1.40 

2 

Lincoln   Neb      .  .   ...    ........ 

338,488 

Little  Rock,  Ark  

39,100 

10,975 

2.52 

659,733 

1.35 

Lowell   Mass      

2,000 

2.10 

Ly  n  n  ,  Mass  

3,667 

295,730 

19,180 

2.08 

126,432 

1.97 

4,027 

1.75 

5 

Minneapolis,  Minn  , 

60,198 

1.60 

10 

Mobile,  Ala  

88,000 

Nashville,  Teun  

24,023 

1.73 

Newark,  N.  J  

79,411 

2.05 

35,677 

2.33 

5 

New  Orleans,  La  

30,682 

2.38 

Newport,  Ky  

81,000 

1.52 

New  York,  NY  

337,920 

Norfolk,  Va  

22,000 

1.54 

Omaha,  Neb  

229,124 

j     1.40  ) 
•j      1  78   f 

1  and  10 

Pawtucket,  R.  I  

1,965 

(      *»«o   ) 

2.50 

Peoria,  111  

473  194 

(     1.32   ) 

Philadelphia,  Pa  

1  777  123 

\     1-45  [ 
1  49 

Pittsburg,  Pa  

10  378 

Portland,  Oregon  

16  405 

Providence,  R   I  

8  096 

Quincy,  111  

742  855 

Rochester,  NY  

112  180 

50 

Rockford,  111  

45  830 

1  33 

Saginaw,  Mich  

81  357 

.35 

St.  Joseph,  Mo  

99428 

.65 

St.  Louis,  Mo  

222,605 

1.46 

1 

230 


HIGHWAY   CONSTRUCTION. 


TABLE  XXXVII.— Continued. 

EXTENT  AND   COST  OP  BRICK  PAVEMENT  IN  SEVERAL  LOCALITIES  IN  THE 
UNITED  STATES,  1898-99. 


Square  Yards. 

Cost  of  Construc- 
tion. 

Guaranty 
Period. 
Years. 

St  Paul,  Minn  

14  076 

$1  80 

11  808 

11  979 

1  50 

Seattle,  Wash  

50  430 

2  20 

Sioux  City,  Iowa  

90  844 

]  79 

South  Bend,  Ind  

264  618 

5  500 

Springfield   111  

407  922 

j     1.05   ) 

Springfield    Mass     

29  192 

(     1.24   f 
2  25 

1 

Springfield   Mo  

93  573 

1  80 

115  187 

.;....  1  59 

145  040 

(     1.85   l 

Ionrl   *» 

2,000 

(     1.91   f 

Terre  Haute,  Ind  

92,400 

1.20 

K 

Toledo   O  

468,988 

1.25 

94,000 

1.17 

Trenton,  N.  J..  

120,997 

1.57 

Troy,  N.  Y  

131,000 

1.81 

Utica,  N.  Y  

1  788 

Washington,  D.  C  

13,903 

Waterbury,  Conn  

9  224 

Wheeling,  W.  Va  

308,131 

0.74 

Wilkesbarre   Pa  

72,183 

Williamsport,  Pa  

65,684 

Wilmington,  Del  

191,488 

1  63 

3  675 

2  65 

3 

60,923 

322.  Variety  of  Systems. — Many  patented  systems  of  forming 
brick  pavements  have  been  introduced,  diifering  either  in  the  shape 
and  size  of  the  bricks  or  in  the  method  of  laying  them.  The  fol- 
lowing are  representative  systems : 

The  Hay  den  Paving-block  (Fig.  19 1). — The  shape  and  manner 
of  laying  these  blocks  is  patented.  The  blocks  are  square  in  plan, 
with  deep  hollows  underneath  to  facilitate  burning  and  save  mate- 
rial; the  top  surface  is  flat,  broken  by  indentations,  and  the  edges 
of  the  top  are  bevelled.  The  blocks  are  made  in  two  sizes,  the 
smaller  ones  5£  inches  deep  and  5f  inches  square. 

The  manner  of  laying  these  blocks  is  as  follows :  The  surface  of 
the  street,  being  brought  to  the  required  grade,  is  covered  with  8 
inches  of  broken  stone,  which  is  compacted  by  rolling  or  ramming; 
on  the  broken  stone  a  layer  of  2  or  3  inches  of  sand  is  spread,  on 
which  the  blocks  are  laid.  The  hollows  in  the  bottom  of  the 


BRICK    PAVEMENTS. 


231 


blocks  are  filled  with  moist  sand,  then  laid  in  position,  rammed  to 
.grade,  and  the  joints  filled,  with  hot  pitch. 


FIG.  19e. 

The  cost  of  this  pavement  is  about  $1.92  per  square  yard. 
The  clay  from  which  these  blocks  are  made  is  composed  of 

Silica 76.24  per  cent 

Alumina 16.87 

Iron 16 

Lime 50 

Magnesia , trace 

Alkalies 1.09 

Water 5.14 

100.00  per  cent 

323.  The  Halwood  Block. — These  blocks  are  composed  of  a 
mixture  of  mica  shale,  clay,  and  sand.  The  blocks  measure 
3x4x9  inches,  taking  48  to  a  square  yard.  They  are  laid  on  a 
foundation  of  either  6  inches  of  concrete  or  8  inches  of  broken 
-stone,  joints  filled  with  coal-tar.  The  cost  per  square  yard,  includ- 
ing foundation,  is  from  $2.50  to  $2.10. 


232  HIGHWAY    CONSTRUCTION. 

324.  The  McReynolds  Patent  Brick. — The  patent  consists  in 
the  bricks  having  lugs,  and  in  one  end  of  each  brick  a  recess.  The 
claim  is  that  this  arrangement  permits  the  joint-filling  to  flow 
around  the  brick,  and  that  these  projections  act  as  an  obstruction 
to  the  cement  running  during  hot  weather  to  the  gutter. 

325>  The  Hale  Pavement. — Introduced  in  1873  is  a  patent  pro- 
cess foi  laying  any  brick  for  paving  purposes,  the  novelty  being  in 
the  foundation,  which  consists  of  3  inches  of  sand,  on  which  are 
laid  1-inch  oak  boards  dipped  in  coal-tar.  The  boards  are  laid  either 
lengthwise  or  crosswise  of  the  street.  On  the  boards  a  layer  of  clean 
sand  from  an  inch  to  an  inch  and  a  half  thick  spread,  and  the  bricks 
laid  on  edge,  "  herring-bone  "  fashion,  with  the  joints  filled  with  tar 
or  sand  as  may  be  desired.  This  costs  in  West  Virginia  $1.35  per 
square  yard,  varying  of  course  with  the  cost  of  the  brick  used.  A 
royalty  of  10  cents  per  square  yard  is  charged  by  the  Hale  Com- 
pany for  the  use  of  this  method  (see  Figs.  16  and  17). 

326.  "  Charleston  Plan."— On  the  graded  surface  of  the  street, 
spread  3  inches  of  clean  coarse  sand;  on  this  place  1-inch  oak 
boards  dipped  in  hot  coal-tar;  on  the  boards  spread  a  cushion-coat 
of  clean  sand  l£  inches  deep;  on  this  lay  the  bricks  (common  red) 
on  edge,  "  Herring-bone  "  fashion ;  cover  the  bricks  with  dry  clean 
sand,  and  broom  well  to  fill  the  joints. 

327.  "  Wheeling  Plan/'— The  roadbed  is  first  graded  and  com- 
pacted by  rolling  with  a  5-ton  roller,  then  3  to  7  inches  of  coarse- 
gravel  and  sand  is  spread  and  rolled ;  on  this  the  bricks  are  laid 
with  their  length  at  right  angles  to  the  axis  of  the  street  and  then 
brought  to  a  solid  bearing  by  rolling;   the  joints  are   filled  with 
sand  and  coal-tar,  and  the  surface  covered  with  dry  sand.     Both 
the  common  red  and  special  bricks  are  used. 

328.  Paving-bricks  are  made  at  Kakos  near  Buda  Pesth  from, 
carefully  selected  clay  mixed  with  a  little  lime.     The  bricks  when 
moulded  are  subjected  to  a  pressure  of  about  3500  pounds  per 
square  inch,  and  then  burned  nearly  to  vitrification.     The  product 
is  regular  in  form,  homogeneous,  of  uniform  density,  and  of  great 
resistance  to  wear.     According  to  the  experiments  of  Prof.  Ign&z, 
they  have  supported  without  deformation  or  fissuring  a  maximum 
load  of  over  45,000  pounds  per  square  inch  and  a  mean  load  of 
31,426  pounds  per  square  inch.     A  square  meter(1.196  square  yards) 
of  this  pavement  costs  $3.80.     In  forming  the  paving,  the  soi)  is. 


BRICK   PAVEMENTS.  233 


first  consolidated  and  a  bed  of  ordinary  brick  masonry  is  laid  upon 
it;  the  paving-bricks  are  set  in  mortar,  leaving  a  joint  of  T\  of  an 
inch  between  them  to  be  filled  with  cement.  The  dimensions  of 
the  bricks  are  7.87  X  7.87  X  3.9  inches  and  they  weigh  24  pounds 
each.  It  takes  22  bricks  to  lay  1  square  yard  of  paving.  The  brick 
foundation  is  6  inches  deep.  The  pavement  made  with  these  bricks 
is  easy  to  clean,  does  not  become  slippery,  and  is  pleasant  to  drive 
over.  The  only  objection  is  that  it  is  somewhat  noisy  in  the  nar- 
row streets. 

329.  Iron  Bricks,  so  called,  are  said  to  be    used  satisfactorily 
for  paving  in  Germany.     These  bricks  are  made  by  mixing  equal 
parts  of  finely  ground  red  argillaceous  slate  and  finely  ground  clay, 
with  the  addition  of  95  per  cent  iron-ore.     The  ingredients  thus 
mixed  together  are  then  moistened  with  a  solution  of  25  per  cent  of 
sulphate  of  iron  to  which  fine  iron-ore  is  added;  after  this  the  com- 
pound is  shaped  in  a  press,  dried,  dipped  once  more  in  a  concen- 
trated solution  of  finely  ground  iron-ore,  and  then  baked  in  an  oven 
for  about  48  hours  in  a  reducing-flame. 

330.  Bricks  made  from  blast-furnace  slag  and  scoria  have  been 
tried;  they  are  durable,  but  soon  wear  slippery  and  afford  little  foot- 
hold for  horses.     Ordinary  building-bricks  saturated  with  gas-tar 
have'been  experimented  with  in  Nashville,  Tenn.     The  results  were 
not  satisfactory,  and  the  pieces  of  experimental  paving  have  been 
xemoved. 

331.  Heads  of  Specifications  for  Brick  Pavement. 

(1)  Preparation  of  roadbed. 

(2)  Foundation.     (Concrete.) 

(3)  Quality  of  the  Bricks. — The  bricks  shall  be  manufactured 
from  suitable  clay  containing  not  more  than  one  per  centum  of 
lime. 

They  must  be  burned  especially  for  paving  purposes.  They 
shall  have  a  resistance  to  crushing  of  not  less  than  8000  pounds,  per 
square  inch  on  the  flat,  and  must  not  absorb  more  than  -^J-g-  of 
their  weight  of  water  after  48  hours'  immersion.  They  must  possess 
such  a  degree  of  toughness  that  when  struck  a  quick  blow  with  a 
4-lb.  hand  hammer  on  the  edges,  the  edges  shall  not  spall  or  chip. 

(4)  Size  and  Shape. — They  shall  be  of  a  uniform  size  of  8J  X  4  X  2£ 
inches,  shall  be  square  on  the  edges,  straight,  and  free  from  fire- 
cracks  or  checks  ;  when  broken,  the  fracture  shall  be  smooth  and 


234  HIGHWAY    CONSTRUCTION. 

straight,  not  conchoidal;  and  the  texture  shall  be  uniform  through- 
out and  not  granular. 

(5)  Samples. — Not  less  than  three  bricks  of  the  quality,  size, 
and  shape  proposed  to  be  used  shall  be  furnished  with  each  pro- 
posal, each  brick  to  be  labelled  with  both  the  bidder's  and  maker's 
name  and  address;  these  samples  shall  be  deposited  in  the  office  of 

three  days  oefore  the  time  of  opening  the  bids.  They 
will  be  subjected  to  the  required  tests,  and  the  characteristics  of 
those  deposited  by  the  successful  bidder  will  become  the  standard 
by  which  will  be  tested  all  the  bricks  to  be  furnished  by  him,  and 
no  deviation  from  this  standard  greater  than  one  per  cent  in  any 
particular  will  be  permitted  in  the  bricks  placed  in  the  work. 

(6)  Inspection  and  Culling. — The  bricks  will  be  inspected  after 
they  are  brought  upon  the  ground,  and  all  bricks  which  are  soft, 
cracked,  checked,  overburned,  or  otherwise  defective  in  quality  or 
dimensions   will   be  rejected   and  must  be  immediately  removed 
from  the  line   of  the  work.     The  contractor  must  furnish  such 
laborers  as  may  be  necessary  to  aid  the  inspector  in  the  examination 
and  the  culling  of  the  bricks;  and  in  case  the  contractor  neglect  or 
refuse  to  furnish  said  laborers,  such  laborers  as  in  the  opinion  of 
the  may  be  necessary  will  be  employed  by  said 

,  and  the  expense  thus  incurred  by  will  be  de- 

ducted and  paid  out  of  any  money  then  due  or  which  may  there- 
after become  due  to  said  contractor  under  the  contract  to  which 
these  specifications  refer. 

(7)  Cusliion-coat. — On  the  concrete  foundation  a  layer  of  clean, 
sharp  sand,  free  from  loam  and  pebbles  exceeding  J  inch  in  size, 

will  be  evenly  spread  to  the  depth  of  inches.     A  template 

shall  be  used  for  striking  the  sand  cushion  to  the  exact  shape  of 
the  crown  of  the  street.    This  template  shall  be  made  in  accordance 
with  the  plans  and  directions  of  the  engineer;  it  shall  be  kept 
whole,  true  to  shape,  and  in  good  condition;  it  shall  rest  on  the 
curbs,  and  be  drawn  forward  immediately  before  the  bricks  are 
laid.     Particular  care  must  be  taken  that  the  sand  be  wet  at  the 
time  the  bricks  are  laid. 

(8)  Laying  the  Bricks. — The  bricks  shall  be  set  on  the  cushion- 
coat  in  close  contact  with  each  other,  both  on  sides  and  ends;  they 
will  be  laid  in  parallel  courses  across  the  street,  with  the  length  of 
the  bricks  at  right  angles  to  the  axis  of  the  street.     The  bricks  of 


BRICK    PAVEMENTS.  235 


adjoining  courses  shall  break  joints  by  at  least  3  inches.  At  street- 
intersections  the  bricks  will  be  laid  on  the  diagonal,  as  shown  on. 
the  plans.  .  .  .  Whole  bricks  only  shall  be  used,  except  in  starting 
a  course  or  making  a  closure  and  in  paving  around  manhole- 
heads,  etc. 

The  bricks  shall  be  laid  by  skilled  workmen,  who  shall  stand  on 
the  bricks  already  laid,  and  in  no  case  shall  the  sand  bed  in  front 
of  the  pavement  be  disturbed  or  walked  on  after  having  been 
smoothed  over  and  brought  to  the  required  crown. 

(9)  Ramming. — The  bricks  shall  be  rammed  to  a  solid  bearing, 
with  hand-rammers  weighing  not  less  than  50  pounds,  and  all 
bricks  which  sink  below  the  general  level  must  be  removed  and 
the  sand  bedding  increased  until  the  level  is  uniform. 

As  soon  as  practicable  after  the  ramming  and  rectification,  and 
not  to  exceed  three  days  after  the  bricks 'are  laid,  they  are  to  be 
rolled  with  a  roller  weighing  not  less  than  three  and  not  more  than 
five  tons,  the  surface  of  the  bricks  to  be  swept  clean  before  the 
rolling. 

(10)  Jointing. — After  the  bricks  have1  been  satisfactorily  rolled, 
the  joints  will  be  filled  with  (Portland-cement  grout  made  from 
two  parts  cement  and  one  part  fine,  sharp  sand)  or  (paving-cement 
of  straight-run  coal-tar  pitch  of  standard  quality,  such  as  is  ordi- 
narily numbered  6  at  the  factory). 

After  the  jointing  is  completed  and  inspected,  the  entire  sur- 
face of  the  pavement  shall  be  covered  with  a  layer  of  clean,  sharp 
sand  to  a  depth  of  about  -£  inch  and  the  roadway  barricaded  and 
no  traffic  allowed  on  it  for  ten  days.  At  the  end  of  this  period 
the  contractor  shall  thoroughly  sweep  the  street  and  remove  the 
sweepings. 

(11)  Interpretation  of  specifications. 

(12)  Omissions  in  specifications. 

(13)  Engineer  defined. 
<14)  Contractor  defined. 

(15)  Notice  to  contractors,  how  served. 

(16)  Preservation  of  engineer's  marks,  etc. 
•(17)  Dismissal  of  incompetent  persons. 

(18)  Quality  of  materials. 

(19)  Samples. 

(20)  Inspectors. 


236  HIGHWAY    CONSTRUCTION. 

(21)  Defective  work,  responsibility  for. 

(22)  Measurements. 

(23)  Partial  payments. 

(24)  Commencement  of  work. 

(25)  Time  of  completion. 

(26)  Forfeiture  of  contract. 

(27)  Damages  for  non-completion. 

(28)  Evidence  of  the  payment  of  claims. 

(29)  Protection  of  persons  and  property. 

(30)  Indemnification  for  patent  claims. 

(31)  Indemnity  bond. 

(32)  Bond  for  faithful  performance  of  work. 

(33)  Power  to  suspend  work. 

(34)  Eight  to  construct  sewers,  etc. 

(35)  Loss  and  damage. 

(36)  Old  materials,  disposal  of. 

(37)  Cleaning  up. 

(38)  Personal  attention  of  contractor. 

(39)  Payment  of  workmen. 

(40)  Prices. 

(41)  Security  retained  for  repairs. 

(42)  Payment,  when  made.     Final  acceptance. 

332.  Specifications  for  Brick  Pavements  in  Memphis,  Term. — The 
roadway  between  curb  lines  shall  be  taken  down  to  sub-grade,  care 
being  taken  not  to  plough  within  three  inches  (3)  of  the  sub-grade 
stokes,  which  last  shall  be  carefully  removed  with  pick  and  shovel, 
in  such  manner  as  to  leave  a  true  and  perfect  surface,  which  shall 
be  rolled  down  with  a  5-ton  roller  three  times  before  the  concrete 
foundation  is  laid.  Before  the  sub-grade  foundation  is  finally 
fixed,  all  water  and  gas  pipes  must  be  put  in  and  adjusted;  water- 
pipes  must  be  of  lead,  double  strength,  and  the  gas  of  the  best  gal- 
vanized pipe ;  the  trenches  shall  be  filled  in  layers  of  three  inches, 
and  carefully  rammed  to  within  six  inches  of  sub-grade  and  the 
balance  of  trench  concreted. 

Concrete. — Upon  the  sub-grade  thus  formed  shall  be  spread 
the  concrete  foundation,  composed  of  hard  limestone,  broken  or 
crusb.fid  to  pass  a  two-inch  ring, — the  same  to  be  free  of  all  dirt, 
trash,  etc.,— clean,  sharp  sand  mixed  with  fine  gravel,  and  the  best 
fresh  Louisville  cement,  in  the  following  proportions,  viz.,  one 


BRICK    PAVEMENTS.  237 


measure  of  cement  and  two  of  sand,  thoroughly  mixed,  and  then 
made  into  mortar,  with  the  least  possible  amount  of  water; 
into  this  will  be  put  the  macadam,  which  shall  first  be  well  wet, 
and  the  whole  worked  into  a  concrete  in-  such  quantities  as  will 
produce  a  surplus  of  free  mortar  when  well  rammed.  This  pro- 
portion, when  ascertained,  will  be  regulated  by  measure.  Each 
total  of  concrete  will  be  thoroughly  mixed,  in  suitable  boxes,  with 
hoes  and  shovels,  the  mortar  always  to  be  mixed  fresh  before  being 
applied  to  the  broken  stone.  It  will  then  be  spread  and  at  once 
thoroughly  compacted  by  ramming  with  heavy  cast-iron  rammers, 
until  free  mortar  appears  on  the  surface:  the  whole  operation 
shall  be  done  as  expeditiously  as  possible.  The  upper  surface  will 
be  made  exactly  parallel  with  the  surface  of  the  pavement  to  be 
laid,  by  floating  over  the  surface  with  cement  and  the  straight 
edge.  The  depth  of  concrete  consolidated  shall  not  be  less  than 
nine  (9)  inches.  No  walking  or  driving  shall  be  permitted  on  the 
concrete  when  it  is  setting,  and  it  shall  be  allowed  to  set  for  three 
(3)  days  before  any  pavement  is  laid  on  it. 

Pavement. — On  the  concrete  foundation  thus  prepared  a  bed 
of  clean,  sharp  sand,  free  from  moisture,  two  (2)  inches  deep,  shall 
be  laid.  The  paving  bricks  to  be  used  shall  be  such  as  shall  be 
satisfactory  and  acceptable  to  the  Engineer,  and  shall  conform 
strictly  to  the  samples  offered  by  the  contractor,  and  accepted  by 
the  Engineer  and  the  Council.  The  sand  must  be  brought  to  a 
true  and  perfect  surface,  and  made  to  conform  strictly  to  the  grade 
pegs  set  by  the  Engineer,  by  means  of  a  drag  straight-edge,  seven 
(7)  feet  long,  drawn  over  the  surface,  and  resting  on  two  pieces  of 
scantling  2x4x16  feet  long,  having  planed  surfaces,  the  top  of 
the  sand  bed  being  flush  with  the  grade  pegs.  Upon  this  bed  of 
sand  the  paving  bricks  are  to  be  laid  on  edge,  at  right  angles  to 
the  line  of  curbs,  in  parallel  lines,  in  as  close  contact  as  possible  on 
sides  and  ends;  the  joints  broken  one  with  another,  by  starting  at 
curb-lines  with  half-bricks,  in  alternate  rows,  so  as  to  break  the 
joints.  No  half  or  broken  brick  shall  be  laid  except  at  the  curb- 
lines,  in  order  to  make  closures,  but  the  brick  must  be  laid  whole 
throughout,  except  as  above  named. 

As  the  pavement  is  laid  over  thirty  or  more  feet  at  a  time,  it 
shall  be  thoroughly  rammed  over  three  times  with  a  flat  iron  ram- 
mer, about  one  foot  in  diameter,  weighing  thirty  or  forty  pounds, 


238  HIGHWAY   CONSTRUCTION. 

which,  must  be  done  by  lifting  and  dropping  the  rammer  verti- 
cally. When  the  bricks  have  been  rammed  to  a  solid  bearing  and 
brought  to  a  perfect  surface,  the  interstices  shall  then  be  thor- 
oughly and  completely  filled,  from  bottom  to  top,  with  distilled 
coal-tar  pitch  (known  as  No.  6)  heated  up  to  300  degrees.  All 
crevices  must  be  filled,  and  the  entire  top  surface  covered  to  a 
depth  of  not  less  than  one  fourth  inch,  and  upon  this  must  be 
spread  one  fourth  inch  of  clean,  sharp  sand,  which  must  be  com- 
paratively dry  and  free  from  moisture.  This  sand  must  be  thrown 
evenly  over  the  boiling  pitch  as  rapidly  as  the  pavement  is  filled 
in,  and  the  pitch  spread  over  the  surface  of  pavement,  the  aim  and 
object  being  to  make  the  pavement  one  solid  mass,  which,  when 
completed,  shall  be  practically  a  fixture  and  water-tight.  The 
bricks  shall  be  rigidly  inspected  before  being  laid  in  the  pavement,, 
and  all  objectionable  ones  removed.  The  sand  and  pitch  shall  be 
acceptable,  and  shall  also  be  applied  as  directed  by  the  Engineer,  or 
his  assistant,  and  to  his  entire  satisfaction  and  acceptance.  The 
pavement,  when  completed,  must  be  smooth,  and  conform  to  the 
grades  given  by  the  Engineer. 

Dimensions  of  Brick. — Square-edged,  to  wit:  Length,  8f- 
'inches;  thickness,  2f  inches;  width,  4  inches.  Halwood  block> 
patent  length,  9  inches;  width,  4  inches;  thickness,  3  inches. 

Bricks  thoroughly  burned  throughout  to  vitrification. 

333.  Extracts  from  Specifications  for  Laying  Brick  Pavements 
in  the  City  of  Bloomington,  111. 

Roadbed. — The  roadbed  shall  be  carefully  graded  and  shaped 
to  an  elevation  of  at  least  eleven  inches  below  the  established  grade 
line  given  by  the  City  Engineer,  and  intended  for  the  surface  of 
the  pavement  when  completed.  The  City  Engineer,  or  his  assist- 
ant, shall  set  all  grade  stakes,  and  thereafter  the  same  must  be 
protected  and  maintained  by  the  contractor  and  his  employees  un- 
til the  services  of  the  same  are  no  longer  needed.  The  contractor 
shall  do  all  necessary  grading  and  shall  provide  all  earth  necessary 
for  filling,  and  dispose  of  all  surplus  excavation  by  removing  the 
same  to  the  lawns  or  other  dirt  streets  as  the  City  Engineer  may 
direct.  In  order  to  bring  the  roadbed  to  the  proper  shape  and 
grade,  a  pattern  made  under  the  direction  of  the  City  Engineer, 
giving  the  street  proper  convexity,  shall  be  continuously  used  as  a 
guide  to  the  graders.  After  said  roadbed  is  properly  graded  and 


BRICK    PAVEMENTS.  239 


shaped  it  shall  be  thoroughly  rolled  and  compacted  by  the  steam 
roller,  wherever  it  is  practicable  to  use  said  roller;  and  wherever  the 
use  of  the  steam  roller  is  impracticable  the  foundation  shall  be  com- 
pacted either  by  the  use  of  the  smaller  roller  or  by  tamping.  The 
roadbed,  being  properly  rolled,  shall  then  be  covered  with  cinders 
of  a  uniform  depth  of  at  least  three  inches,  and  the  same  shall  be 
rolled  and  compacted  as  before;  and  there  shall  then  be  spread  a 
covering  of  sand  of  sufficient  thickness  to  grade  the  surface  of  said 
roadbed  to  a  uniform  shape,  regular  and  smooth  surface  for  receiv- 
ing the  bottom  course  of  brick.  Should  any  depressions  appear 
during  the  process  of  rolling,  such  as  the  settlement  of  sewer 
branches  or  otherwise,  the  same  must  at  once  be  filled  up  and 
again  rolled,  so  that,  when  the  process  of  rolling  shall  cease,  the 
entire  roadbed  shall  be  uniform  and  complete  in  its  settlement. 

Brick  Work. — There  shall  then  be  placed  a  course  of  brick 
upon  their  flat  surface,  long  dimensions  parallel  with  the  street, 
laid  as  closely  together  as  practicable  and  all  joints  broken.  Dry 
sand,  screened,  will  then  be  spread  over  the  entire  course  of  brick, 
and  well  brushed  in  so  as  to  completely  fill  all  crevices.  Sufficient 
screened  sand  will  then  be  placed  on  the  bottom  course  of  brick  to 
make  a  bed  of  one  inch  depth  upon  which  to  place  the  top  course 
of  brick.  The  top  course  of  brick  will  then  be  laid  on  their  longest 
two-inch  surface  across  the  street,  breaking  joints  and  laying  the 
brick  as  closely  together  as  possible.  Nothing  less  than  whole  bricks 
to  be  used  in  the  top  course  except  were  necessary  to  break  joints. 
The  courses  of  brick  in  the  top  course  must  be  kept  straight  across 
the  street,  at  right  angles  to  the  curbing  as  near  as  practicable.  Brick 
that  are  badly  swelled  and  irregular  will  not  be  permitted  in  the 
top  course.  They  must  constitute  a  good  quality  of  "  paving-brick," 
maintaining  uniformity  and  regularity  in  shape  to  such  a  degree  as 
will  be  consistent  with  a  first-class  pavement,  and  render  satisfac- 
tion to  the  Engineer  in  charge.  The  bottom  course  of  brick  must 
be  composed  of  a  good  quality  of  such  as  are  known  as  "sidewalk 
brick."  The  top  course  of  brick,  having  been  laid  a$  above  provid- 
ed, must  then  be  covered  with  screened  sand  and  rolled  with  a 
roller  weighing  at  least  two  tons.  During  this  final  process  of 
rolling  the  sand  must  continually  be  brushed  into  the  pavement 
so  as  to  effectually  fill  all  crevices.  All  such  work  shall  be  under 
the  supervision  and  subject  to  the  approval  of  the  Engineer. 


240  HIGHWAY   CONSTRUCTION. 


834.  Specifications  for  brick  pavements  differ  widely  in  their 
requirements.  As  yet  no  standard  method  of  construction  or  of 
testing  the  quality  of  the  brick  has  been  arrived  at. 

A  variety  of  methods  of  construction  are  in  vogue,  and  each  one 
has  its  advocates  and  opponents.  Thus  we  find  in  one  place  a  foun- 
dation of  sand,  in  another  sand  and  boards,  in  another  gravel,  in 
others  broken  stone  laid  in  the  form  of  a  Telford  foundation,  in 
others  broken-stone  concrete,  and  so  on. 

As  to  the  quality  of  the  brick  no  definite  requirements  have 
been  determined.  In  the  absence  of  determined  qualities  it  has  of 
course  been  impossible  to  adopt  a  uniform  system  of  tests,  and  the 
majority  of  tests  published  are  of  little  value  from  this  want  of 
uniformity. 

The  specifications  relating  to  the  quality  of  the  brick  to  be  used 
are  generally  vague;  the  majority  recite  that  "the  brick  used  shall 
be  hard,  free  from  defects  of  any  kind,  manufactured  and  burned 
especially  for  street-paving  purposes,  be  equal  in  all  respects  to  the 
sample  filed  with  the  proposal,  and  subject  to  inspection  and  ac- 
ceptance or  rejection  by  the  engineer  or  inspector."  This  state- 
ment of  the  qualities  required  defines  in  reality  but  very  little. 
The  term  hard  is  an  indefinite  one;  a  hard  brick  in  one  locality 
may  be  known  as  a  soft  one  in  another.  Without  a  definite  state- 
ment as  to  what  constitutes  defects  there  may  be  differences  of 
opinion  as  to  whether  or  not  they  exist  in  a  given  article,  as  well  as 
to  the  equality  of  goods  furnished  with  the  sample  deposited. 

The  characteristic  qualities  and  strength  of  the  material  are  not 
clearly  defined,  or  in  such  manner  as  will  enable  the  bidder  to  cor- 
rectly interpret  the  meaning.  The  power  to  accept  or  reject, 
although  nominally  in  the  hands  of  the  engineer,  is  indefinite  and 
unsupportable,  because  the  acceptance  or  rejection  cannot  be  made 
in  accordance  with  known  provisions  and  fixed  rules.  In  the 
absence  of  recognized  standards  two  courses  are  open  in  order  to 
secure  the  desired  qualities,  avoid  indefiniteness  and  controversy; 
namely,  (1)  to  reserve  the  right  to  make,  before  awarding  the  con- 
tract, any  test  that  the  engineer  may  see  fit  to  make,  and  award 
the  contract  in  accordance  with  the  results  of  such  tests;  or  (2) 
prescribe  in  the  specifications  the  definite  tests  to  which  the  mate- 
rial will  be  subjected,  with  such  reservations  as  to  time  and  placo 
as  the  exigencies  of  each  particular  place  seem  to  demand. 


BRICK    PAVEMENT',.  •  241 

334a.  Extract  from  Paving-brick  Specifications. — ST.  Louis, 
Mo. — "  The  bricks  shall  not  be  less  than  eight  inches  nor  more 
than  nine  inches  long,  not  less  than  two  and  one-half  inches  nor 
more  than  three  and  one-half  inches  wide,  not  less  than  four  inches 
nor  more  than  four  and  one-half  inches  deep,  with  rounded  edges 
with  a  radius  of  three-eighths  of  an  inch.  Said  brick  shall  be  of 
the  kind  known  as  l  repressed  '  brick,  and  shall  be  repressed  to  pro- 
duce a  mass  free  from  internal  flaws,  cracks,  or  laminations. 

"  The  bricks  shall  be  uniform  in  size  and  quality,  and  thoroughly 
burned  and  annealed. 

"All  bricks  so  distorted  in  burning  or  with  such  prominent 
kiln-marks  as  to  produce  an  uneven  pavement  shall  be  rejected. 

"  Each  bidder  shall  submit  one  hundred  bricks,  which  shall  be 
subjected  to  such  physical  tests  as  may,  in  the  opinion  of  the 
Street  Commissioner,  be  necessary  to  determine  their  quality  and 
suitability  for  the  work. 

"To  secure  uniformity  in  bricks  of  approved  manufacture,  de- 
livered for  use,  the  following  tests  shall  be  made: 

"  1.  They  shall  show  a  modulus  of  rupture  in  cross-breaking  of 
not  less  than  twenty-five  hundred  pounds  per  square  inch. 

"  2.  Specimen  bricks  shall  be  placed  in  the  machine  known  as 
the  "rattler,"  twenty-eight  inches  in  diameter,  making  thirty 
revolutions  per  minute.  The  number  of  revolutions  for  a  standard 
test  shall  be  eighteen  hundred,  and  if  the  loss  of  weight  by  abrasion 
or  impact  during  such  test  shall  exceed  thirty  per  cent  of  the  orig- 
inal weight  of  the  bricks  tested,  then  the  bricks  shall  be  rejected. 
An  official  test  to  be  the  average  of  two  of  the  above  tests. 

"  No  bid  contemplating  the  use  of  rejected  brick  shall  be  enter- 
tained. 

"  Samples  may  be  submitted  by  manufacturers,  in  which  case 
the  bidders  proposing  to  use  brick  of  such  manufacture  will  not  be 
required  to  submit  samples.  The  quality  of  the  brick  furnished 
must  conform  to  the  samples  presented  by  the  manufacturers  and 
kept  in  the  office  of  the  Street  Commissioner. 

"  The  Street  Commissioner  reserves  the  right  to  reject  any  and 
all  bricks  which,  in  his  opinion,  do  not  conform  to  the  above  speci^ 
fications." 


242  HIGHWAY   CONSTRUCTION. 

The  specifications  for  vitrified  block  differ  from  the  above  only 
in  the  following  particulars: 

Dimensions. — The  blocks  shall  not  be  less  than  nine  inches  nor 
more  than  twelve  inches  long,  not  less  than  three  and  one-half 
inches  nor  more  than  four  and  one-half  inches  wide,  not  less  than, 
five  inches  nor  more  than  six  inches  deep. 

Rattler  Test. — When  tested  in  the  rattler,  under  the  above  con- 
ditions, if  the  loss  exceeds  twenty-five  per  cent  of  the  original 
weight,  then  the  blocks  shall  be  rejected. 

334b.  Rumbling  in  Brick  Pavements. — The  rumbling  is  caused 
by  vacant  spaces  between  the  brick  and  the  foundation.  These 
spaces  may  be  formed  in  a  number  of  ways.  If  the  sand  bed  is. 
carelessly  made  or  not  properly  compacted,  the  settlement  will 
leave  a  space  between  the  bed  and  the  brick;  if  the  rows  of  brick, 
are  keyed  up  too  tightly,  they  are  forced  off  the  sand  bed  a  slight 
distance,  which  is  sufficient  to  transmit  a  rumbling  sound;  or  the 
same  result  is  obtained  if  the  brick  are  not  rolled  sufficiently  to 
force  them  solidly  into  the  sand  bed.  Lime  in  the  material  used  for 
joint-filler  will,  by  swelling,  cause  the  brick  to  rise  from  the  foun- 
dation. 

It  is  now  thought  that  the  tendency  to  lift  may  be  remedied  by 
introducing  at  intervals  of  25  or  30  feet  across  the  street,  and  on 
both  sides  of  the  street  at  the  curb,  an  expansion-joint  of  pitch,  so 
that  any  movement  of  the  pavement  due  to  swelling  of  the  filler  or 
to  change  in  temperature  will  be  taken  up  by  the  elasticity  of  the 
pitch-joints. 

334c.  Number  of  Brick  and  Block  Required  per  Square  Yard. 

Tmrio  TSTAm*>  Number         Weight  of 

per  Yd.         1  brick,  Ibs. 

Mack  repressed  brick 60  6.88 

Mack  (Lug)  repressed  brick. 58  7.06 

Corning  repressed  brick a 60  6.40 

Johnson  burg  repressed  brick 63  6.81 

Preston  repressed  brick 62  6.04 

McMahon-Porter  repressed  brick 56  7.07 

Park  repressed  brick 59  6.31 

Park  (wire-cut)  brick 58  6.35 

Metropolitan  (repressed)  block 43  9.98 

Nelsonville  repressed  block 42  9.50 

Mack  (Lug)  repressed  block 44  9.11 


BRICK   PAVEMENTS.  243 


Trade  Name.                                               Number  Weight  of 

per  Yd.  1  brick,  Ibs. 

Townsend  repressed  block 46  8.60 

Athens  repressed  block 42  9.50 

Harris  repressed  block 43  9.00 

Bolivar  repressed  block 44  8.25 

Guise  repressed  block 46  9.25 

Park  repressed  block 40  9.30 

Eastern  repressed  block 46  9.25 

McMahon-Porter  repressed  block 43  9.14 

Clearfield  repressed  block , 48  8.20 

Clearfield  (wire-cut)  block 47  8.56 

334d.  Brick  Paving  for  Country  Roads.— Brick  is  being  success- 
fully used  for  paving  country  roads,  both  as  a  substitute  for  broken 
stone  and  in  localities  where  good  stone  is  not  obtainable,  and  also 
in  combination  with  broken  stone.  The  first  experiment  with 
brick  for  this  purpose  was  made  at  Monmouth,  111.,  where  a  strip 
of  pavement  3000  feet  long  and  7  feet  wide  was  constructed,  at  a 
cost  of  $2650.  The  method  of  construction  was  as  follows  :  The 
earth  road-bed  was  graded  and  formed  to  the  proper  contour.  The 
curbing  to  hold  the  brick  in  place  was  made  of  2  x  6-inch  oak 
plank  set  7  feet  apart,  and  held  in  place  by  oak  stakes  18  inches 
long,  driven  4  feet  apart  ;  in  the  space  inclosed  by  the  curbs  a  sand 
bed  5  inches  thick  was  formed  and  shaped  to  the  required  contour; 
on  this  was  placed  a  single  course  of  No.  1  paving-brick  set  on  edge, 
and  the  joints  were  filled  with  sand.  Outside  the  curbing  broken 
stone  was  placed  for  a  width  of  2  feet,  thus  making  the  width  of 
the  improvement  11  feet.  The  earth  road  on  each  side  of  the 
paved  strip  was  graded  and  formed  to  afford  trackways  for  use  in 
dry  weather.  The  total  width  of  the  road  being  40  feet. 

The  use  of  brick  for  the  construction  of  trackways  has,  been 
suggested  by  Engineering  News.  The  advantages  of  such  track- 
ways would  be  the  same  as  stated  in  Art.  439  under  Stone  Track- 
ways. 

The  details  of  construction,  such  as  the  foundation,  under  the 
bricks,  the  construction  of  the  broken-stone  pavement  at  their 
sides  and  between  them,  the  material  for  filling  the  joints  between 
the  bricks,  drainage,  etc.,  will  have  to  vary  with  local  circum- 
stances. The  method  of  construction  adopted  must  make  provi- 
sion against  the  tilting  of  the  brick  under  loads  crossing  them,  and 


244 


HIGHWAY    CONSTRUCTION. 


also  against  their  displacement  by  frost.     To  provide  against  the 
first,  a  rough  stone  curb  may  be  used,  as  shown  in  Fig.  19c.     If 


FIG.  1 9c.— CROSS-SECTION  MACADAM  ROAD  WITH  BRICK  TRACK- 
WAY. 

stone  is  not  available,  brick  set  on  edge,  artificial  stone,  or  fire-clay 
curbing  may  be  used. 

Where  provision  has  to  be  made  for  drainage,  the  construction 
may  be  as  shown  in  Fig. 


FIG.  1  9o.— CROSS-SECTION  BRICK  TRACKWAY  UNDERDRAINED. 

The  ditch  above  the  drain-tile  may  be  filled  with  any  coarse 
materials — field-stone  or  quarry-spalls  too  soft  or  gravel  too  large 
for  road-covering — or  with  lumps  of  burnt  clay.  The  filling  to  be 
thoroughly  compacted  by  ramming.  The  space  between  the  brick 
strips  and  outside  them  to  be  covered  with  gravel,  an.d  the  joints 
between  the  bricks  filled  with  sand. 


BRICK    PAVEMENTS. 


245 


334e.  Average  Price  of  Paving-brick  per  Thousand  in  1898. 


State. 

Price. 

State. 

Price. 

$14.00 

Massachusetts       

$9  00 

12.78 

8  88 

Connecticut      and      Rhode 

8  70 

12  58 

West  Virginia.  ... 

8  69 

Maryland             

12  00 

Arkansas 

8  40 

Alabama  

11  50 

Iowa                     • 

8  20 

New  York  

10  99 

Nebraska            .         .  . 

8  OD 

Michigan 

10  76 

District  of  Columbia 

8  02 

Virginia     .           

10  00 

Greortna 

8  02 

10  00 

Montana  

8  00 

9  93 

Kansas  

7  24 

9.42 

7  11 

Indiana  

9  88 

Ohio 

6  92 

Texas  

9  83 

Utah  ;  

5  45 

9  11 

Kentucky  .   . 

9  00 

Average  for  United  States 

$848 

In  1897  the  ereueral  averasre 

was.  . 

.  .$8.22 

CHAPTEE  VII. 
BROKEN-STONE  PAVEMENTS. 

335.  As  near  as  can  be  ascertained,  the  first  broken-stone  pave- 
ments were  constructed  in  France  in  1764  by  one  M.   Tresaguet, 
who  built  many  miles  of  such  pavements  in  the  latter  part   of  the 
last  century.     In  the  early  part  of  the  present  century  two  systems 
were  introduced  into  England,  the  first  by  Telford,  the  second  by 
Macadam. 

336.  The  name  of  Telford  is  associated  with  a  rough  stone  foun- 
dation, which  he  did  not  always  use,  but  which  closely  resembled 
that  which  had  been  previously  used  in  France.     Macadam  disre- 
garded this  foundation,  contending  that  the  subsoil,  however  bad, 
would  carry  any  weight  if  made  dry  by  drainage  and  kept   dry  by 
an  impervious  covering.     The  names  of  both  have  ever  since  been 
associated  with  the  class  of  road  which  each  favored,  as   well  as 
with  roads  on  which  all  their  precepts  have  been  disregarded. 

337.  The  following  specifications  show  the  difference  in  the 
methods  of  the  inventors. 

338.  Tresaguet's  Method,    1764   (Fig.  21).— "The   bottom  of 
the  foundation  is  to  be  parallel  to  the  surface  of  the  road.     The 
first  bed  or  foundation  is  to  be  placed  on  edge  and  not  on  the 
ilat,  in  the  form  of  a  rough  pavement,  and  consolidated  by  beat- 
ing with  a  large  hammer;   but  it  is  unnecessary*  that  the  stones 
should  be  even  one  with  the  other.    The  second  bed  is  to  be  equally 
placed  by  hand,  layer  by  layer,  and  beaten  and   broken   coarsely 
with  a  large  hammer,  so  that  the  stones  may  wedge  together  and 
no  empty  spaces  remain.     The  last  bed,  three  inches  in  thickness, 
is  to  be  broken  to  about  the  size  of  a  nut  with  a  small  hammer,  on 
a  sort  of  anvil,  and  thrown  upon  the  road  without  a  shovel  to  form 
the  curved  surface.     Great  attention  must  be  given  to  choose  the 
hardest  stone  for  the  last  bed,  even  if  one  is  obliged  to  go  to  more 

246 


BROKEK-STONE    PAVEMENTS. 


distant  quarries  than  those  which  furnish  the  stone  for  the  body  of 
the  road.  The  solidity  of  the  road  depending  on  this  latter  bed,  one 
<jannot  be  too  scrupulous  as  to  the  quality  of  the  materials  which 
^ire  to  be  used  for  it." 


Fig.20.    FRENCH.  PREVIOUS  TO    1775, 


Fig.21.          TRESAGUET. 


Fig.22. 


TELFORD. 


Fig.23.        MACADAM 


339.  Telford's  Method,  1824  (Fig.  22).—"  Upon  the  levol  bed 
prepared  for  the  road  materials  a  bottom  course  or  layer  of  stones 
is  to  be  set  by  hand  in  the  form  of  a  close  firm  pavement.  The 
stones  set  in  the  middle  of  the  road  are  to  be  sever!  inches  in 
depth;  at  nine  feet,  from  the  centre,  five  inches;  at  twelve  feet 


248  HIGHWAY    CONSTRUCTION. 

from  the  centre,  four  inches;  and  at  fifteen  feet  from  the  centre, 
three  inches.  They  are  to  be  set  on  their  broadest  edges  lengthwise 
across  the  road,  and  the  breadth  of  the  upper  edge  is  not  to  ex- 
ceed four  inches  in  any  case.  All  the  irregularities  of  the  upper 
part  of  the  said  pavement  are  to  be  broken  off  by  the  hammer, 
and  all  the  interstices  to  be  filled  with  stone  chips  firmly 
wedged  or  packed  by  hand  with  a  light  hammer,  so  that  when  the 
whole  pavement  is  finished  there  shall  be  a  convexity  of  four  inches 
in  the  breadth  of  fifteen  feet  from  the  centre. 

"  The  middle  eighteen  feet  of  pavement  is  to  be  coated  with  hard 
stones  to  the  depth  of  six  inches.  Four  of  these  six  inches  to  be 
first  put  on  and  worked  in  by  carriages  and  horses;  care  being 
taken  to  rake  in  the  ruts  until  the  surface  becomes  firm  and  con- 
solidated, after  which  the  remaining  two  inches  are  to  be  put  on. 

"  The  whole  of  this  stone  is  to  be  broken  into  pieces,  as  nearly 
cubical  as  possible,  so  that  the  largest  piece  in  its  largest  dimen- 
sions may  pass  through  a  ring  of  two  and  one  half  inches  inside 
diameter. 

"  The  paved  spaces  on  each  side  of  the  middle  eighteen  feet  are 
to  be  coated  with  broken  stones  or  well-cleaned  gravel  up  to  the 
footpath  or  other  boundary  of  the  road,  so  as  to  make  the  whole 
convexity  of  the  road  six  inches  from  the  centre  to  the  sides  of  it, 
and  the  whole  of  the  materials  are  to  be  covered  with  a  binding  of 
an  inch  and  a  half  of  good  gravel  free  from  clay  or  earth." 

340.  Macadam's  Method  (Fig.  23). — Macadam  omitted  the  foun- 
dation of  large  stones,  claiming  that  it  was  not  only  useless  but 
injurious ;  he  placed  on  the  natural  soil  a  layer  of  stone  broken 
equally  into  cubes  of  about  one  and  a  half  inches  in  their  greatest 
dimensions,  and  spread  equally  over  the  surface  of  the  road  to  a 
depth  of  ten  or  twelve  inches.  Binding  material  was  not  used,  the 
stone  being  left  to.  work  in  and  unite  by  its  own  angles  under  the 
traffic.  Macadam  preferred  the  test  of  weight  to  that  of  measure- 
ment, and  insisted  that  no  stone  should  weigh  more  than  six 
ounces,  which  is  the  weight  of  a  cube  of  one  and  a  half  inches  of 
hard  compact  limestone;  his  overseers  were  provided  with  small 
scales  and  a  six-ounce  weight  to  test  the  larger  stones. 

Although  Macadam  was  the  pioneer  of  good  road  construction 
in  England,  and  from  whose  name  the  word  macadamized  is  de- 
rived, it  may  be  observed  that  he  had  been  anticipated  in  the  pro- 


BROKEN-STONE    PAVEMENTS.  249 

mulgation  of  the  system  of  a  regularly-broken  stone  covering  by 
Mr.  Edgeworth,  an  Irish  proprietor,  whose  treatise  on  roads,  of 
which  the  second  edition  was  published  in  1817,  contains  the  re- 
sults of  his  experiments  on  the  construction  of  roads,  with  some 
useful  rules.  He  advocated  the  breaking  of  the  stones  to  a  small 
size,  and  their  equal  distribution  over  the  surface.  He  also  recom- 
mended that  the  interstices  should  be  filled  with  small  gravel  or 
sharp  sand — a  practice  which,  though  condemned  by  Macadam,  is 
now  adopted  by  the  best  roadmakers.* 

341.  Since  Telford  and  Macadam's  time  the  practice  of  road- 
making  has  been  greatly  improved  by  the  introduction  of  rollers 
and  stone-crushing  machinery. 

342.  Modern  Telford. — On  the  natural-soil  bed,  properly  graded, 
a  layer  of  stones  eight  inches  thick  is  set  by  hand,  arranged  and 
wedged  as  described  by  Telford.    On  the  stone  foundation  so  prepared 
a  layer  of  broken  stone  of  a  size  not  exceeding  three  inches  is  evenly 
spread  and  rolled ;  the  surface  so  rolled  is  covered  with  a  layer  of 
sand  one-half  inch  thick,  and  the  rolling  continued ;  then  a  layer 
of  stones  not  larger  in  any  dimension  than  two  inches  is  spread  to 
a  depth  of  four  inches  and  rolled,  followed  as  before  with  a  layer 
of  sand  and  also  rolled.     Finally  a  coating  of  clean  sharp  sand  is 
applied,  well  watered,  and  the  rolling  continued  until  the  surface 
becomes  smooth.     The  surplus  sand  is  then  swept  off  and  removed. 

343.  Modern  Macadam  pavements  are  constructed  in  the  man- 
ner above  described,  only  omitting  the  stone  foundation,  and  the 
depth  of  the  stone  varies  from  four  to  twelve  inches. 

344.  Defects  of  the  Telford  System. — (1)  No  matter  how  care- 
fully the  interstices  between  the  foundation-stones  are  filled  with 
chips,  a  large  percentage  of  voids  is   left   giving  free   access  to 
water,  thus  defeating  the  object  of  the  covering,  which  is  to  pre- 
serve the  natural  soil  from  contact  with  water.     The  pavement 
acts  as  a  drain;  the  natural  soil  becomes  saturated  with  water, 
and  a  slow  but  constant  sinking  of  the  bottom  stone  into  the  sub- 
soil and  a  slow  but  gradual  rising  of  the  natural  soil  takes  place, 

*  Renuie  also  brought  into  use,  eight  or  ten  years  before  Macadam,  the 
system  of  broken-stone  road  construction  in  connection  with  the  formation  of 
the  road-surface  upon  many  of  the  bridges  built  by  him,  notably  the  bridge 
commenced  in  1809,  afterwards  known  as  Waterloo  Bridge,  where  upon  a 
compacted  clay  foundation  a  layer  of  fine  gravel  was  rolled  in  to  receive  a 
coating  of  flints  broken  to  the  size  of  an  egg. 


250  HIGHWAY   CONSTRUCTION. 

the   cohesion   of   the   superstructure   is   destroyed,  and   it   finally 
becomes  a  mass  of  mud  and  stones. 

(2)  If  the  foundation  be  of  a  harder  rock  than  the  covering,  it 
becomes  an  anvil  on  which  the  softer  stones  are  pounded  to  pieces 
by  the  passing  loads. 

(3)  The  stone  foundation  unnecessarily  increases  the  cost  of 
•construction.      The  roads  of  Central  Park,  N.  Y.,  are   excellent 
examples  of  the  Telford  system.     They  are  of  indefinite  thickness, 
reposing  on  a  bed  of  thoroughly  drained  earth;   they  were  con- 
structed and  are  maintained  at  a  cost  that  is  prohibitory  to  an  exten- 
sive use  of  such  pavements. 

345.  Defects  of  the  Macadam  System.  —  The  broken  stone  laid 
as  directed  by  Macadam  cannot  be  impervious,  because  the  inter- 
stices compose  one  half  of  the  bulk  of  loosely  spread  stones,  and  no 
amount  of  rolling  will  reduce  the  voids  more  than  one  fourth;  and 
as  nature  abhors  a  vacuum,  the  subsoil  when  moistened  will  rise  up 
and  fill  the  vacant  space,  and  the  weight  of  the  traffic  will  force  the 
lower  stones  down  until  the  whole  becomes  a  mass  of  mud  and 
stones,  as  shown  by  the  following  analysis  of  a  portion  of  the  crust 
of  the  macadamized  roads  in  the  Mall,  St.  James  Park,  London  : 

ANALYSIS  OF  MACADAMIZED  ROAD  CRUST. 

Mud  ..........................................  11.00  cu.  ft.  or  41.00  per  cent 

Sand  with  pebbles  not  exceeding  -^  of  an  inch.  .  .  2.40      "      "9  " 

Stones  from  ^  to  i  inch  ........................  6.56      "       "24 

"     itoliuch  ____  ...  ..................  4.48      "      "  16£ 

"      ItoSiinches  ......................  2.56      "      "    9£ 


Total  volume  .........  27.00  cu.  ft.  or  100.00  percent 

From  this  analysis  it  appears  that  less  than  9  -J-  per  cent,  say 
one  tenth  of  the  original  stone,  escaped  underground,  whilst  40  per 
cent  of  it  was  reduced  to  the  state  of  mud. 

346.  Advantages  of  Broken-stone  Pavements. 

(1)  Good  foothold. 

(2)  Reasonably  easy  traction  when  in  good  condition. 

(3)  Moderate  first  cost. 

(4)  Comparatively  noiseless. 

347.  Defects  Common  to  all  Broken-stone  Pavements. 
(1)  Mud  when  wet. 


BROKEN-STONE    PAVEMENTS.  251 

(2)  Dust  when  dry. 

(3)  Excessive  cost  of  maintenance  under  heavy  traffic. 

(4)  Impossibility  of  keeping  them  clean. 

348.  The  foregoing  defects  condemn  the  use  of  broken  stone 
for  city  streets,  yet  when  properly  built  and  maintained  broken 
stone  forms  the  pleasantest,  safest,  and  most  economical  road- 
surface  known  for  city  suburbs  and  country  highways. 

Ideally  perfect  broken-stone  road  construction  has  never  been 
attained,  and  never  will  be  until  our  road  constructors  abandon    ^ 
obsolete   precedents   and    construct    road-coverings    that  will   be 
adapted  to  the  requirements  of  the  traffic  and  impervious  to  water 
and  frost. 

349.  Essentials  Requisite  to  Successful  Construction. — The  essen- 
tials requisite  to  the  successful  construction  of  broken-stone  pave- 
ments may  be  summed  up  as  follows : 

(1)  The  entire  removal  from  the  roadbed  of  all  vegetable  or 
perishable  matter. 

(2)  The  removal  of  the  natural  soil  to  such  depth  as  may  be 
determined  by  its  character,  and  by  the  thickness  of  the  intended 
covering. 

(3)  Sub-surface  drainage  wherever  required. 

(4)  The  thorough  compacting  of  the  natural-soil  bed. 

(5)  The  employment  of  sand  or  gravel  for  the  foundation. 

(6)  The  employment  of  the  best  materials  afforded  by  the 
locality. 

(7)  The  employment  of  unscreened  stones. 

(8)  The  complete  exclusion  of  clay  or  loam  from  the  broken 
stone.       ,  : 

(9)  The  employment  of  sand  or  gravel  for  binding,  in  sufficient 
quantity  to  fill  the  voids. 

(10)  The   thorough   compacting  of   the   broken  stone   with   a 
roller  of  competent  weight  and  suitable  form. 

350.  Erroneous  Methods  of  Construction.— Broken-stone  pave- 
ments can  be  made  very  unsatisfactory  and  defective  by: 

(1)  A  permeable  foundation. 

(2)  By  the  use  of  excessively  hard  stones  which  no  amount  of 
rolling  will  consolidate. 

(3)  By  the  use  of  improper  binding  material,  such  as  loam  and 

clay. 


252  HIGHWAY   CONSTRUCTION". 

(4)  By  an  undue  proportion   of   soft  among  hard  stones.     A 
email  quantity  (about  one  fourth)  of  soft  stones  judiciously  mixed 
with  the  harder  will  be  an  undoubted  advantage. 

(5)  By  employing  stones  of  too  large  a  size. 

(6)  By  screening  the  broken  stone,  thus  removing  the  chips  and 
dust  which  otherwise  would  assist  in  filling  the  voids.     Screening 
should  not  be  practised,  except  when  an  injurious  amount  of  clay 
or  loam  has  become  mixed  with  the  stone. 

(7)  By  assorting  the  stone  and  laying  it  in  layers  according  to- 
the  size  of  the  stone.     The  practice  of  forming  a  road  with  strata 
of  screened  stone  assorted  in  different  sizes  and  growing  smaller 
and  smaller  towards  the  top  is  erroneous ;  the  smaller  stone  will  find 
its  way  to  the  bottom,  and  the  larger  stone  will  work  to  the  surface 
and  ruts  will  be  quickly  formed.     It  will  be  porous,  and  no  matter 
how  heavily  rolled  it  will  be  continually  crumbling. 

(8)  By  covering  the  surface  of  the  compacted  stone  with  a  layer 
of  stone-dust. 

(9)  By  the  use  of  an  excessive  quantity  of  binding  material. 

(10)  By  the  use  of  an  excessive  quantity  of  water  when  rolling. 

351.  Quality  of  the  Stones. — The  materials  used  for  broken-stone 
pavements  must  of  necessity  vary  very  much  according  to  the  locality. 
Owing  to  the  cost  of  haulage,  local  stone  must  generally  be  used 
especially  if  the  traffic  be  only  moderate.     If,  however,  the  traffic  is 
heavy,  it  will  sometimes  be  found  better  and  more  economical  tc« 
obtain  a  superior  material,  even  at  a  higher  cost,  than  the  local 
stone ;  and  in  cases  where  the  traffic  is  very  great,  the  best  material 
that  can  be  obtained  is  the  most  economical. 

352.  The  qualities  required  in  a  good  road  stone  are  hardness 
and  toughness  and  ability  to  resist  the  disintegrating  action  of  the 
weather.     These  qualities  are  seldom  found  together  in  the  same 
stone.     Igneous  and  silicious  rocks,  although  frequently  hard  and 
tough,  do  not  consolidate  so  well  nor  so  quickly  as  limestone,  owing 
to  the  sandy  detritus  formed  by  the  two  first  having  no  cohesion, 
whilst  the  limestone  has  a  detritus  which  acts  like  mortar  in  bind- 
ing the  stones  together. 

353.  A  stone  of  good  binding  nature  will  frequently  wear  much 
better  than  one  without  although  it  is  not  so  hard.     A  limestone 
road  well  made  and  of  good  cross-section  will  be  more  impervious 
to  wet  than  any  other,  owing  to  this  cause,  and  will  not  disintegrate 


BROKEN-STONE    PAVEMENTS.  253 

so  soon  in  dry  weather,  owing  partly  to  tins  and  partly  to  the  well- 
known  quality  which  all  limestone  has  of  absorbing  moisture  from 
the  atmosphere.  Mere  hardness  without  toughness  is  not  of  much 
use,  as  a  stone  may  be  very  hard  but  so  brittle  as  to  be  crushed  to 
powder  under  a  heavy  load,  when  a  stone  not  so  hard  but  having 
a  greater  degree  of  toughness  will  be  uninjured. 

By  a  stone  of  good  binding  quality  is  meant  one  that,  when 
moistened  by  water  and  subjected  to  the  pressure  of  loaded  wheels 
or  rollers,  will  bind  or  cement  together.  This  quality  is  possessed 
to  a  greater  or  less  extent  by  nearly  all  rocks  when  in  a  state  of 
disintegration.  The  binding  is  caused  by  the  action  of  water  upon 
the  chemical  constituents  of  the  stone  contained  in  the  detritus 
produced  by  crushing  the  stone,  and  by  the  friction  of  the  frag- 
ments on  each  other  while  being  compacted  ;  its  strength  varies 
with  the  different  species  of  rock,  but  it  exists  in  some  measure 
with  them  all,  being  greatest  with  limestone  and  least  with  gneiss. 

The  essential  condition  of  the  stone  to  produce  this  binding 
effect  is  that  it  be  sound.  No  decayed  stone  retains  the  property 
of  binding,  though  in  some  few  cases,  where  the  material  contains 
iron  oxides,  it  may,  by  the  cementing  property  of  the  oxide,  un- 
dergo a  certain  binding. 

The  first  attempt  to  ascertain  the  cementing  property  of  rocks 
was  made  by  the  Massachusetts  Highway  Commission.  The 
method  followed  is  described  in  Art.  356«. 

These  tests  show  in  general  that  quartzites,  sandstones,  gran- 
ites, gneisses,  and  marble  possess  very  little  cementing  power,  some 
of  them  breaking  down  with  two  or  three  blows;  whereas  lime- 
stones and  some  trap-rocks  show  a  high  power  of  cementation  and 
stand  thirty  or  forty  blows  before  giving  way.  Other  trap-rocks 
have  not  proved  so  good. 

354.  The  durability  of  stones  used  for  roads  depends  partly 
upon  resistance  to  chemical  decomposition  and  partly  upon  resist- 
ance to  mechanical  abrasion.  The  former  character  is  influenced 
mainly  by  the  chemical  composition  of  the  constituent  materials, 
while  the  latter  depends  upon  the  manner  in  which  and  the  ma- 
terial by  which  these  component  minerals  are  aggregated  into  a 
compact  mass.  To  know  thoroughly  the  qualifications  of  any  rock 
as  a  road-stone,  therefore,  involves  an  intimate  knowledge  of  both 


254  HIGHWAY    CONSTRUCTION". 

its  mineralogical  composition  and  its  structure.  Some  of  the  ap- 
parently hard  and  durable  rocks,  such  as  certain  granites  and  ba- 
salts, which  remain  comparatively  unaltered  when  in  the  solid 
crust  of  the  earth  and  removed  from  the  disintegrating  influence 
of  air  and  water,  when  broken  up  and  exposed  to  the  chemical  in- 
fluences prevailing  on  the  surface  of  a  road  rapidly  decompose  into 
clayey  mud.  Other  rocks,  such  as  many  of  the  sandstones,  are 
chemically  almost  indestructible,  but  are  so  loosely  aggregated  to- 
gether that  under  the  action  of  traffic  they  crumble  into  powder. 
As  regards  the  structure,  its  character  is  influenced  by  the  size  of 
the  grains  (within  certain  limits  the  coarser  the  grain  the  weaker 
the  crushing-strength  of  the  stone),  the  orientation  of  the  crystals, 
and  the  nature  of  the  base  or  matrix  in  which  these  crystals  are 
imbedded.  Many  of  the  crystalline  rocks  are  merely  an  aggregate 
of  crystal  grains  wedged  together  into  a  tight-fitting  mosaic.  The 
breaking  down  or  decomposition  of  one  of  the  component  minerals 
seriously  diminishes  the  cohesion  of  such  rocks.  In  other  cases 
there  is  much  more  intimate  union  of  the  crystals,  which  are 
interlocked  in  such  a  manner  that  the  cohesion  is  increased.  In 
others  the  crystalline  particles  are  firmly  set  in  a  more  or  less  com- 
pact siliceous  paste  or  cement  of  considerable  hardness  and  dura- 
bility, and  forming  a  continuous  matrix,  which  would  hold  to- 
gether even  if  the  crystals  themselves  decayed.  As  regards  the 
mineralogical  constituents,  a  vast  difference  exists  in  the  chemical 
durability  of  different  minerals.  Feldspar,  which  forms  a  consid- 
erable proportion  of  the  composition  of  the  great  majority  of  rocks 
used  for  roads,  occurs  in  many  different  varieties,  some  of  which — 
the  potash  feldspars — are  much  more  durable  than  those  which 
contain  a  large  proportion  of  soda  or  lime.  With  regard  to  the 
durability  of  minerals  a  distinction  must  be  drawn  between  chem- 
ical disintegration  or  decomposition  and  alteration.  Many  minerals 
are  liable  to  alteration  without  any  loss  of  cohesive  power.  In  some 
cases  there  is  often  a  distinct  gain  in  the  chemical  durability  of 
such  altered  minerals.  Among  minerals  of  this  kind  may  be  men- 
tioned the  ferro-magnesian  silicates,  which  readily  alter  into  ser- 
pentinous  products  of  great  stability.  The  mere  presence,  there- 
fore, of  an  unstable  element  in  a  rock  is  not  necessarily  of  itself 
unfavorable,  unless  the  result  of  its  alteration  is  such  that  disinte- 


BROKEN-STONE   PAVEMENTS.  255- 

gration  ensues,  as  when  feldspar  breaks  clown  into  a  powdery  clay. 
Hardness,  though  important  when  combined  with  other  qualities,, 
is  singly  riot  of  great  consequence.  Quartz,  the  hardest  of  the 
common  minerals,  used  alone  does  not  make  a  desirable  road-stone, 
as  its  dust  is  lacking  in  cementing  power;  it  has  a  low  specific 
gravity  and  is  very  brittle.  Brittleness  promotes  crumbling  under 
the  impact  of  traffic.  Soft  rocks,  as  limestones  and  slates,  are 
quickly  ground  to  powder  and  are  rapidly  carried  away  by  water 
and  wind  action. 

The  most  efficient  road-stones  are  obtained  from  the  class  of 
rocks  called  traps,  or  dike-stones,  and  technically  known  as  diabases 
and  diorites.  These  rocks  are  not  uniformly  desirable,  but  nearly 
all  of  them  are  better  than  the  best  of  other  rocks.  The  normal 
composition  of  the  diabase  rocks  is  feldspar  and  pyroxene,  with  or 
without  black  mica.  The  diorites  may  be  considered  as  the  same 
rock  with  the  mineral  hornblende  replacing  the  pyroxene.  The 
structure  of  these  rocks  is  such  that  the  minerals  composing  them 
are  interlocked  with  one  another  in  the  most  perfect  manner,  thus 
producing  great  toughness.  To  the  effect  of  this  structure  must 
be  added  the  uniform  toughness  of  the  individual  minerals  pyroxene 
and  hornblende.  The  feldspars  present  in  the  diabases  and  diorites 
are  essentially  alumino-silicates  of  calcium  and  sodium,  and  they 
form  one  of  the  unstable  compounds,  under  the  influences  of  their 
environment,  on  which  depends  so  largely  the  rapid  disintegration 
of  these  rocks.  When  these  rocks  are  fresh,  little  loss  from  this 
cause  is  to  be  apprehended  during  the  life  of  the  road;  but  where 
the  weathered  portion  of  the  rock,  the  sap,  is  used,  the  loss  sus- 
tained by  chemical  and  mechanical  means  is  considerable.  The 
alteration  of  feldspar  to  clay,  quartz,  and  calcite  in  many  cases  so- 
weakens  the  coherency  of  the  rocks  that  they  readily  crumble  to- 
powder  under  pressure  and  are  converted  into  fine  sand.  The 
calcite  derived  from  the  alteration  of  the  feldspar,  when  deposited 
from  solution  during  dry  periods,  acts  to  a  limited  extent  as  a  bind- 
ing material,  tending  to  strengthen  the  rock-dust  and  increase  its 
attachment  to  the  broken  stone.  The  experiments  of  the  Massa- 
chusetts Highway  Commission  shows  that  the  maximum  cementing- 
value  of  powdered  rock  was  obtained  from  an  olivine  diabase  which 
was  much  weathered.  Some  diabases  carry  a  considerable  percent- 


256  HIGHWAY    CONSTRUCTION. 

age  of  black  mica,  which,  owing  to  its  tabular  form  and  the  readi- 
ness with  which  it  cleaves  into  thin  plates,  is  quickly  and  easily 
transported  by  the  winds.  The  essential  mineral  pyroxene  and  the 
occasional  mineral  pyrite  in  diabases,  and  the  hornblende  in 
diorite,  are  also  prone  to  decomposition,  a  change  which  is  aided  by 
the  presence  of  acids. 

The  granite  rocks  are  undesirable  for  use  as  road-stones.  Many 
of  them  contain  more  or  less  of  the  soda  and  lime-bearing  feld- 
spars, in  addition  to  the  potash  variety,  and  their  durability  is  in 
consequence  adversely  affected.  No  granite  can  be  found  whose 
feldspar  is  free  from  some  secondary  alteration  to  clay,  and  when 
this  change  has  gone  on  to  a  degree  sufficiently  great  to  affect  the 
strength  of  the  stone  it  should  be  discarded  as  unfit  for  broken- 
stone  roads.  Granites  in  this  condition  quickly  crumble  to  sand 
and  clay,  and  the  winds  sweep  away  the  fine  material  in  dry 
weather,  while  in  rainy  times  the  road  is  in  a  muddy  state.  There 
are  several  kinds  of  mica  present  in  granite  rocks.  Of  these  mus- 
covite  or  white  potash  mica  is  much  more  durable  than  the  black 
ferro-magnesian  mica,  biotite.  This  circumstance  is  proved  by  the 
fact  that  white  mica  is  a  much  more  frequent  constituent  of  the 
sedimentary  sands  and  clays  derived  from  the  breaking  up  of 
granite  rocks  than  is  biotite  or  black  mica.  The  mica  is  very 
easily  transported  both  by  wind  and  water  action,  owing  to  its 
tabular  character,  and  this  mineral  under  all  circumstances  is  unde- 
sirable in  road-stone.  Other  constituents  of  granite,  such  as 
pyrites  and  iron  oxides,  are  also  notably  unstable.  A  true  granite 
is  composed  of  -quartz,  orthoclase,  feldspar,  and  two  micas — biotite 
and  muscovite.  The  micas  are  not  always  present,  their  place 
being  wholly  or  in  part  taken  by  hornblende  or  pyroxene.  When 
a  granite  is  free  from  mica  it  offers  great  resistance  to  wear,  but 
its  brittleness  and  its  granular  structure  operate  to  increase  the 
rate  of  abrasion.  Granite  differs  from  the  trap-rocks  not  only  in 
mineral  composition,  but  also  in  an  entire  difference  in  the  form 
and  arrangement  of  the  constituent  minerals;  in  the  granites  the 
structure  is  granular,  with  little  tendency  toward  an  interlocking 
arrangement.  The  brittleness  of  granite  is  due  principally  to  the 
quartz,  one  of  the  hardest  as  well  as  most  brittle  minerals  of  com- 
mon occurrence.  When  the  necessities  of  the  case  force  the  use  of 


BROKEN-STONE    PAVEMENTS.  257 

granite  rocks  it  is  well  to  select  those,  such  as  syenites  or  granites, 
containing  as  small  a  percentage  of  inica  and  quartz  as  possible. 
Syenite  if  badly  weathered  is  considered  even  more  objectionable 
than  granite.  Although  granite  and  syenite  contain  a  great 
amount  of  feldspar,  the  cementing  value  of  these  rocks  is  much 
less  than  that  possessed  by  the  diabases  and  diorites. 

Gneiss  and  mica  schists  are  either  too  soft  or  too  brittle  to 
withstand  the  action  of  traffic.  The  micaceous  element  causes  the 
stones  to  break  up  and  grind  away  quickly.  The  hornblende 
schists,  although  rather  soft  and  easily  ground  up,  have  consider- 
able toughness,  and  in  the  absence  of  better  material  will  make  tol- 
erable roads. 

Limestone  rocks,  though  they  vary  considerably  in  hardness, 
are  in  general  much  too  soft  for  economical  use  in  road-making, 
provided  any  other  more  suitable  material  can  be  obtained.  The 
variety  of  such  stone  which  is  known  as  dolomite  commonly  affords 
a  better  rock  than  calcite,  or  ordinary  limestone.  Where  the  lime 
is  commingled  with  clay  the  effect  is  generally  to  improve  its  value 
as  a  road  material;  where  the  mixture  is  of  sand  and  the  mass  is 
an  arenaceous  limestone,  it  is  generally  poor  road-stone.  Where 
the  surface  of  a  limestone  road  can  be  covered  with  iron  ore  the 
firmness  of  the  mass  is  much  increased. 

Crystalline  limestone  or  marble  is  unsuitable,  for,  while  the  mate- 
rial binds  well  together,  it  is  brittle,  and  consequently  quickly  passes 
into  a  condition  of  dust  under  the  action  of  the  traffic.  Its  granular 
or  crystalline  structure  has  a  very  pronounced  tendency  to  break  up 
into  rhombic  grains,  a  tendency  which  serves  further  to  increase 
the  weakness  of  the  stone.  The  white  powdery  dust  produced  is 
very  offensive.  The  limestones  suffer  a  considerable  loss  from  the 
ready  solubility  of  the  calcite  in  rain-water  and  water  impregnated 
with  acids.  Rain-water  charged  with  carbonic  acid  will  dissolve 
when  cold  one  part  of  lime  carbonate  in  10,800  parts  of  water.  In 
the  magnesiau  or  dolomitic  limestones  the  loss  from  this  cause  is 
somewhat  less,  but  still  important.  The  carboniferous  and  transi- 
tion limestones  are  fairly  durable  and  make  smooth  and  pleasant 
roads  for  light  traffic  and  pleasure-drives. 

Quartz,  when  it  is  found,  as  is  sometimes  the  case,  in  large 
veins  in  which  it  has  been  deposited  from  water  at  depths  below 


258  HIGHWAY    CONSTRUCTION. 

the  original  surface,  often  affords  a  tolerable  material  for  macadam 
purposes.  Owing  to  the  very  angular  forms  which  the  material 
assumes  when  crushed,  it  mats  well  together.  The  bits,  however, 
are  not  really  cemented  into  a  mass,  for  the  dust,  unlike  that  from 
most  other  rocks,  does  not  form  a  binding  cement.  Moreover, 
under  the  pressure  of  wheels  and  the  beating  of  horses'  feet,  the 
material  passes  rapidly  into  the  state  of  fine  sand,  which  is  blown 
or  washed  away.  Roads  of  this  material  rarely  attain  a  very 
smooth  state,  and  they  wear  out  rapidly. 

Quartzites  are  rocks  w'hich  were  originally  sandstone  the  frag- 
ments of  which  have  to  a  greater  or  less  extent  been  dissolved  and 
recemented  into  a  firm  mass.  The  nature  of  quartzites  varies 
greatly.  They  are  generally  hard,  but  brittle,  and  break  up  rap- 
idly under  the  action  of  traffic,  forming  a  fine  sand  much  like  pow- 
dered glass.  The  smooth  surface  of  the  fragments  prevents  their 
forming  a  bond.  Mixed  with  limestone  they  form  fair  roads. 

Chert  consists  of  quartzose  material  which  has  been  segregated 
in  beds  of  limestone  rock.  When  the  limestone  decays  and  is 
washed  away,  the  cherty  matter  is  often  left  in  a  rubble-like  mass, 
In  many  cases  the  material  verges  into  quartzite  and  is  indistin- 
guishable from  it.  The  cherty  residuum  arising  from  the  decay  of 
limestone  is  of  value  in  road-making  in  the  southern  portion  of  the 
Appalachians  and  in  other  portions  of  this  country  beyond  the  gla- 
ciated field,  and  also  in  some  of  the  States  of  the  Northwest. 

Field-stone  and  river-stone  have  been  much  used  in  some  dis- 
tricts of  England;  they  generally  make  a  rough  road,  as  they  are 
composed  of  the  hardest  parts  of  those  stones  which  have  resisted 
the  action  of  the  weather,  and  are,  though  frequently  very  hard,  of 
unequal  hardness,  so  that  they  wear  very  irregularly. 

From  the  results  obtained  on  experimental  paving-strips  and  in 
the  laboratory  the  following  conclusions  have  been  deduced  as  to 
the  relative  wearing  value  of  different  rocks: 

One  cubic  yard  of  basalt  having  a  resistance  to  crushing  of 
24,040  pounds  per  square  inch  is  equal  to — 

Pounds 
per  square  inch. 

1.10  cubic  yards  of  basalt  with  a  crushing  strength  of     21,015 
1.34      "          ft        "       "          "      "         "  "          "      19,200 

1.70      "  "        "       "  "      "         "  "          "      16,780 


BROKEN-STONE    PAVEMENTS. 


Pounds 
per  square  inch.. 

3.00  cubic  yards  of  coral     limestone    with    a    crushing 

strength    of  ....................     1  1,750' 

3.80      "  "        "  coral     limestone    with     a    crushing 

strength    of  ................  ...      10,810 

5.80      "  "        "   Triass-ic  with  a  crushing  strength  of       9,670 

7  to  8    "  "        "   sandstone        "         "  i(          "        8,390 

9  to  11  "  "        "  cretaceous       "         "  "          "        7,260 

unequal  hardness,  so  that  they  wear  very  irregularly. 

355.  Coefficients  of  quality  for  various  road  materials  have  been* 
obtained   by  the  engineers  of  the  French  "Administration   des- 
Fonts  et  Chaussees."    The  quality  was  assumed  to  be  in  inverse  pro- 
portion to  the  quantity  consumed  on  a  length  of  road  with  the 
same  traffic,  and  measurements  were  systematically   made  of  the" 
traffic  and  wear  to  arrive   at   correct  results,  these  processes  re- 
quiring great  care  and  considerable  time.    Direct  experiments  on 
resistance  to  crushing  and  to  abrasion  and  collision  were  made  on 
673   samples   of   road   materials   of  all   kinds.      The   coefficients. 
obtained  by  these  experiments  were  found  to  agree  fairly  well  with 
those  arrived  at  by  actual  observation  of  the  wear  in  the  roads,  and 
are  summarized  in  Table  XXXVIII.     The  coefficient  20  is  equiva- 
lent to  "  excellent,"  10  to  "  sufficiently  good/'  and  5  to  "  bad." 

356.  The  experiments  were  conducted  as  follows:  The  apparatus 
employed  to  determine  the  resistance  to  wear  consisted  of  cylindrical 
boxes  of   iron  about  8   inches   in  diameter  and  13  inches  long,. 
mounted  on  an  axle  revolving  horizontally,  and  so  cranked  as  to 
hold  the  axes  of  the  boxes  at  an  angle  of  30  degrees  with  the  axis- 
of  revolution.     In  each  box  was  placed  5  kilograms  of  the  broken. 
materials  to  be  tested,  carefully  cleansed  from  dust  by  washing,  ami 
the  boxes  put  in  motion  at  a  rate  of  2000  revolutions  per  hour,. 
The  stones  rolled  against  one  another,  and  were  thrown  from  one> 
end  of  the  box  to  the  other  at  each  revolution.     After  5  hours  or 
10,000  revolutions  the  boxes  were  opened,  the  detritus  resulting: 
from  the  rubbing  and  collision  was  carefully  collected  and  sorted, 
and  the  weight  of  all  of  less  diameter  than  -fa-  inch,  compared  with. 
that  of  the  original  samples,  gave  the  degree  of  wear.    It  was  found 
that  the  best  materials  seldom  gave  less  than  20  grams  of  detritus 
per  kilogram,  and  the   coefficient   of   20  was,  therefore,  adopted 


260 


HIGHWAY    CONSTRUCTION. 


for  materials  having  that  proportion  of  wear.     For  other  materials 
the  coefficient  was  derived  from  the  proportion 

Grams  of  detritus   :  20   :  :  20  :  coefficient. 

Eesistance  to  crushing  was  determined  by  means  of  an  hydraulic 
press.  Experience  having  shown  that  cubes  of  the  hardest  ma- 
terials rarely  resisted  more  than  3000  kilograms  per  square  centi- 
meter (equal  to  about  19  tons  per  square  inch)  the  coefficient  of  20 
was  given  to  materials  presenting  that  degree  of  resistance,  and 
other  coefficients  were  derived  from  the  proportion 

3000  :  crushing  weight  per  square  centimeter  : :  20  :  coefficient. 

In  the  experiments  every  precaution  to  insure  accurate  results 
was  taken.  When  the  materials  were  already  rounded,  as  pebbles, 
they  did  not  wear  much  in  the  machine,  and  obtained  a  coefficient 
far  above  their  value;  and  there  were  anomalies  with  a  few  other 
materials,  such  as  chalk  flints  with  a  softer  coating,  and  stones  with 
cavities.  The  size  to  which  the  stones  were  broken  did  not  seem  to 
have  much  influence  on  the  wear. 

TABLE  XXXVIII. 
COEFFICIENTS  OF  QUALITY. 


Materials. 

Coefficient  of  Wear. 

Coefficient  of 
Crushing. 

Basal  t                            ...             

12.5K 
14.1 
10.3 
7.3 
11.6 
14.5 
13.8 
14.3 
12.9 
9.8 
3.5 
6.6 

)24.2 
22.9 
19.0 
18.0 
12.7 
15.3 
30.0 
26.2 
17.8 
21.3 
16.8 
15.7 

12.1  t 
8.3 

13.4 
7.7 
12.4 
7.2 
12.3 
9.9 
12.3 
14.2 
17.8 
6.5 

j!6 
16.3 
14.8 
15.8 
13.0 
11.1 
21.6 
16.6 
13.2 
17.6 
25.5 
13.5 

Qrauit6                        ....       .   ....    . 

Syenite         .    

Slaa:.  . 

Outirtzite                        

Quartzose  sandstone     

Quartz     

Silex                                   

Chalk  flints     :... 

Limestone 

356a.  Abrasion  and  Cementation  Tests  of  Stone. — The  report  of 
the  Massachusetts  Highway  Commission  for  1896  describes  in 
detail  the  methods  employed  at  the  Lawrence  Scientific  School  of 
Harvard  University  for  testing  the  qualities  of  road-building 
stone. 


BROKEN-STONE    PAVEMENTS.  261 

In  making  the  tests  the  aim  has  been  to  determine  the  nature 
of  the  qualities  which  constitute  fitness  or  unfitness  of  the  different 
rocks  used  for  road-making,  the  effects  of  diverse  methods  of  treat- 
ment used  in  the  process  of  construction,  and  the  relative  value  of 
the  bed-rocks  and  gravels  which  are  found  in  different  parts  of  the 
State. 

The  machines  used  were  designed  by  Prof.  L.  W.  Page.  The 
abrasion-machine  was  modelled  after  the  Deval  machine  used  by 
the  French  engineers  for  determining  the  relative  value  of  the 
stone  used  in  the  construction  and  maintenance  of  the  national 
highways  of  France. 

The  machine  employed  for  the  abrasion  tests  consists  of  four 
cylinders,  each  7.9  inches  in  diameter  and  13.4  inches  deep,  fast- 
ened to  a  shaft  so  that  the  axis  of  each  makes  an  angle  of  30 
degrees  with  the  axis  of  rotation.  Each  cylinder  is  closed  at  one 
end  and  has  a  tightly  fitting  cover  at  the  other.  At  one  end  of  the 
shaft  is  a  pulley  by  which  the  cylinders  are  revolved,  and  at  the 
other  end  is  a  revolution-counter.  Four  tests  can  be  carried  on  at 
the  same  time. 

The  stone  to  be  tested  is  broken  into  pieces,  between  2-£  inches 
and  li  inches  in  diameter,  and  carefully  washed  to  remove  any 
foreign  matter.  In  a  test  5  kilograms  (11.15  pounds)  of  stone  are 
placed  in  a  cylinder,  the  cover  is  bolted  on,  and  the  cylinder  is 
rotated  at  the  rate  of  2000  revolutions  per  hour  for  five  hours.  At 
each  revolution  of  the  shaft  the  fragments  of  stone  are  thrown 
twice  from  one  end  of  the  cylinder  to  the  other,  grinding  them 
against  each  other  and  against  the  sides  of  the  cylinder.  At  the 
end  of  five  hours  the  machine  is  stopped,  the  cylinder  opened,  and 
the  contents  are  emptied  into  a  sieve  having  y^-inch  meshes.  The 
material  passing  through  the  sieve  is  put  aside  for  the  cementation 
test.  The  sieve  and  the  stone  remaining  in  it  are  thoroughly 
washed,  and  the  cylinder  is  washed  to  remove  the  dust  that  adheres 
to  it.  The  washed  stones  are  thoroughly  dried  and  weighed,  the 
decrease  giving  the  weight  of  the  detritus  worn  off  by  the  test. 
The  percentage  of  the  detritus  is  rarely  less  than  20  grams  per 
kilogram  of  stone  used  (2$);  therefore  20  has  been  adopted  as  the 
standard,  and  the  coefficient  of  quality  is  obtained  by  the  following 
formula : 


262  HIGHWAY    CONSTRUCTION. 

20      400 

q  —  20  X  —  — ,  u  =  per  cent, 

u.        u 

in  which  u  represents  the  weight  in  grams  (15.43  grains)  of  detri- 
tus per  kilogram  (2.23  Ibs.)  of  stone. 

After  several  tests  had  been  made  in  the  manner  above  de- 
scribed, it  was  recognized  that  the  very  important  property  or 
cementing  value  of  the  stone  was  not  investigated.  The  commis- 
sion, recognizing  this  deficiency,  accordingly  directed  its  attention 
to  devising  some  means  of  supplying  it.  As  no  previous  attempt 
had  been  made  in  this  direction,  the  commission  had  to  invent  its 
own  method,  which  is  as  follows: 

The  stone-dust  to  be  tested  is  obtained  either  from  the  detritus 
of  the  abrasion  test  or  by  specially  reducing  the  stone.  The  dust 
is  prepared  by  passing  it  through  an  automatic  screen,  which  con- 
sists of  a  cylinder  (39.37  inches  long  by  4  inches  in  diameter)  of 
brass  wire  netting  of  five  different  meshes :  100  meshes  per  inch  at 
one  end  and  decreasing  by  20  meshes  each  time  to  20  meshes  per 
inch  at  the  other  end,  the  smallest  size  being  at  the  end  where 
the  dust  enters.  The  screened  dust  is  mixed  with  distilled  water 
and  placed  in  a  circular  metal  die;  a  closely  fitting  plug  is  then 
inserted  on  top  of  the  wet  dust,  and  a  pressure  of  1422  pounds 
per  square  inch  is  applied.  The  compressed  briquette,  circular  in 
section,  0.98  inch  in  diameter,  and  of  the  same  height,  is  removed 
irom  the  die  and  laid  aside  for  two  weeks,  so  that  it  may  become 
thoroughly  dry. 

The  weight  of  the  dust  varies  with  the  density  and  compressi- 
bility of  the  stone,  but  generally  about  0.9  ounce,  and  0.24  cubic 
inch  of  distilled  water  is  required  to  make  a  briquette  of  the  above 
dimensions. 

The  dried  briquettes  are  tested  by  impact  in  a  specially  devised 
machine,  which  consists  of  a  hammer,  weighing  2.2  pounds,  ar- 
ranged like  the  hammer  of  a  pile-driver.  It  is  raised  by  a  screw, 
und  dropped  automatically  from  any  desired  height,  falling  on  a 
plunger  which  rests  on  the  briquette.  The  plunger  is  held  in  two 
guides,  and  attached  to  it  is  a  lever  pivoted  at  £  of  its  length  from 
the  plunger,  and  carries  a  pencil  at  its  free  end.  The  pencil  has  a 
vertical  parallel  movement  five  times  as  great  as  that  of  the  plunger, 


BROKEN-STONE   PAVEMENTS. 


263 


and  its  movement  is  registered  on  a  drum  against  which  the  pencil 
presses.  The  drum  rotates  through  a  small  angle  at  each  stroke  of 
the  hammer;  thus  an  automatic  diagram  is  taken  on  the  behavior 
of  the  briquette  throughout  the  whole  test.  The  standard  fall  of 
the  hammer  for  a  test  is  0.39  inch,  and  the  blow  is  repeated  until 
the  bond  of  cementation  of  the  material  is  destroyed.  The  final 
blow  is  easily  ascertained,  for  when  the  hammer  falls  on  the  plunger, 
if  the  material  beneath  it  can  withstand  the  blow,  the  plunger  re- 
bounds; if  not,  the  plunger  stays  at  the  point  to  which  it  is  driven. 
The  number  of  blows  needed  to  break  the  bond  is  taken  as  repre- 
senting the  binding  power  of  each  stone,  and  is  so  used  in  compar- 
ing this  property  in  road  materials. 

As  the  surface  of  a  broken-stone  road  is  constantly  abraded  and 
recemented,  it  was  considered  desirable  to  determine  the  recement- 
ing  properties  of  the  stone  tested.  Briquettes  differing  from  those 
described  above  only  in  that  they  were  of  constant  weight  instead 
of  constant  height  were  made  and  tested  in  the  manner  described 
.above,  and  then  were  remade  and  retested. 

The  table  on  page  264  contains  some  of  the  results  of  these 
tests. 

356b.  Coefficients  of  wear  and  cementing  quality  of  the  rocks 
of  Maryland  have  been  obtained  by  the  Highway  Division  of  the 
Maryland  Geological  Survey  by  the  same  methods  described  in  Art. 
,  and  are  as  follows: 

Coefficient  of  Wear.      Cementation  Test. 


Trap-rocks 

Serpentine , 

Granitic  and  quartzitic. 

Limestones 

Sandstones , 


5.7-26.1 
5.8-21.2 
2.6-16.3 
4.8-16.8 
5.  -13. 


1-  10 
10-300 
1-  13 
1-  73 
0-  28 


The  figures  signify: 


Wear.  Cementation. 

1-7  1-4 bad. 

7-12  4-10 fair, 

12-17  10-20 good. 

17-  20-  excellent. 


.'  - 

UN!>  ) 


264 


HIGHWAY    CONSTRUCTION. 


i« 


60 


11 

JLB 
QOfl 


i^Iall 


lllllll 


5l  • 


t:  a 


£  5 


H      . 

g    d 

O    2 

II 


3§I 


BROKEN-STO^E    PAVEMENTS.  265 

357.  Size  of  Stones. — The  stones  should  be  broken  into  frag- 
ments as  nearly  cubical  as  possible.     The  size  of  the  cubes  will 
depend  upon  the  character  of  the  rock.     If  it  be  granite  or  trap, 
they  should  not  exceed  1|  inches  in  their  greatest  dimensions;  if 
limestone,  they  should  not  exceed  2  inches. 

358.  The  smaller  the  stones  the  less  the  percentage  of  voids. 
Small  stones  compact  sooner,   require  less  binding,  and  make  a 
smoother  surface  than  large  ones. 

359.  It  is  not  necessary  nor  is  it  advisable  that  the  stones  should 
be  all  of  the  same  size ;  they  may  be  of  all  sizes  under  the  maximum. 
In  this  condition  the  smaller  stones  fill  the  voids  between  the  larger 
and  less  binding  is  required. 


FIG.  24.-SIZE  AND  SHAPE  OF  STONE  FOR  BROKEN- 
STONE  PAVEMENTS. 

The  proper  shape  of  broken  stone  is  shown  in  Fig.  24. 

360.  Breaking  the  Stone.— Breaking  stone  for  the  purpose  of 
using  it  as  a  road-covering  was  until  quite  recently  always  effected 
by  hand;  now  by  the  use  of  machinery  it  is  more  quickly  and 
cheaply  broken. 

361.  Hand-broken  stone  still  finds  favor  with  European  en- 
gineers ;  they  claim  that  it  is  better  broken  and  has  sharper  angles 
than  that  broken  by  crushing :    and  in  many  districts  the  occupa- 
tion  affords   employment   for   persons   who   otherwise   would    be 
thrown  upon  the  public  for  support. 

362.  In  breaking  stone  by  hand  the  breaker  sits  and  strikes  the 
stone  with  a  small  cast-steel  chisel-faced  hammer,  weighing  about 


266  HIGHWAY    CONSTRUCTION. 

one  pound,  fixed  at  the  end  of  a  long,  straight-grained  but  flexible 
ash  stick.  The  breaker  also  has  another  hammer,  weighing  about 
five  pounds,  with  which  he  reduces  the  size  of  the  large  stones  before 
breaking  them  into  proper  size.  Each  breaker,  is  furnished  with  a 
gauge-ring  through  which  the  stones  must  pass  in  every  direction. 

363.  The  great  cost  of  hand-broken  stone  led  to  the  employ- 
ment of  machine  crushers;  their  use  effected  a  reduction  in  the 
cost  of  from  50  to  200  per  cent,  and  increased  the  amount  of  daily 
output  from  1  to  50. 

364.  The  objections  to  machine-broken  stone  are  principally: 

(1)  Want  of  uniformity  in  the  size  of  stones. 

(2)  The  stone  is  frequently  flaky  with  rounded  edges,  which  is 
a  very  disadvantageous  form  for  compacting. 

(3)  Very  tough  stones  have   frequently  to   be  passed  several 
times  through  the  machine  before  they  get  properly  broken. 

(4)  Very  soft  stones  are  crushed  to  powder. 

365.  Cost  of  Breaking  Stone.— The  cost  of  breaking  stone  by 
hand  will  vary  considerably  in  different  localities  on  account  of  the 
character  of  the  stones  to  be  broken  and  the  value  of  labor. 

366.  The  average  amount  of  stone  broken  by  a  good  stone- 
breaker  is  given  by  Mr.  Codrington  in  his  work  on  the  Mainte- 
nance of  Macadamized  Roads  as  follows :  Hard  silicious  stones  and 
igneous  rocks,  I  to  1|  cubic  yards  per  day;  granite,  |  cubic  yard  per 
day;  river  gravel,  field-stones,  or  flints,  3  to  4  cubic  yards  per  day. 

367.  The  cost  of  a  stone-crushing  plant  and  expense  of  operat- 
ing may  be  taken  as  follows : 

Cost  of  crusher,  engine,  and  boiler  set  up,  complete $2500.00 

Cost  of  operating: 

1  engineinaii  and  fireman $3.00 

2  laborers  feeding ' 3.50  » 

2  tons  of  coal 8.00 

Oil,  waste,  etc 2.00 

Repairs 10.00— $26.50 

The  product  will  vary  with  the  toughness  of  the  stone  to  be 
broken  and  the  size  of  the  machine. 

368.  The  wear  and  tear  of  a  stone-crusher  is  very  considerable; 
it  has  been  known  to  reach  as  high  as  62.5  per  cent  of  the  first  cost 
of  the  machine  in  one  year. 


BROKEN-STONE    PAVEMENTS.  267 

369.  To  make  a  stone-breaking  machine  pay,  it  is  necessary — 

(1)  To  give  it  nearly  constant  work. 

(2)  To  exercise  care  in  feeding,  to  give  a  sufficient  supply  with- 
out allowing  an  undue  quantity  of  stone  to  pass  in  at  one  time. 

(3)  That  the  machine  shall  be  so  located  as  to  reduce  to  the 
minimum  the  expense  of  handling  both  the  unbroken  and  the 
broken  stone. 

The  dimensions  and  capacity  of  several  crushers  are  given  in 
Chap.  XXIII. 

370.  It  is  impossible  to  estimate  the  cost  of  getting  the  un- 
broken stone  to  the  crusher  and  the  broken  stone  back  to  the  road, 
for  that  depends  entirely  upon  the  distance  which  must  be  trav- 
ersed in  cartage  and  the  condition  of  the  grounds  over  which  the 
loads  are  hauled.     If  the  loads  have  to  be  hauled  a  considerable 
distance  to  or  from  the  crusher,  or  if  heavy  grades  have  to  be  as- 
cended or  rough  ground  traversed,  the  time  occupied  in  hauling 
each  load  will  be  increased  and  less  can  be  hauled  in  a  day,  thus 
lessening  the  work  done  by  horses  and  drivers  for  each  day's  wages. 

Where  stone  is  to  be  obtained  in  more  than  one  place  along  the 
line  of  the  projected  road,  it  is  sometimes  more  economical  to  take 
the  crusher  to  the  stone  than  to  have  to  haul  the  broken  stone  a 
great  distance.  For  this  purpose  the  crusher  can  be  mounted  on 
wheels  and  the  steam  roller  used  to  haul  and  drive  the  crusher, 
without  the  expense  of  a  fixed  plant  for  crushing  stone. 

371.  Cost  of  Quarrying  and  Crushing  Stone.— The  report  of  the 
Board  of  8treet  Commissioners  of  the  city  of  Hartford,  Conn.,  for 
the  year  1890  contains  the  following  table  of  the  cost  of  quarrying 
and  crushing  stone  for  the  past  ten  years. 

The  increase  in  the  cost  of  quarrying  and  crushing  stone  during 
the  past  year  is  in  part  chargeable  to  the  extra  cost  of  hauling  the 
stone  to  the  crushers,  on  account  of  the  added  distance  at  which 
the  stone  was  procured,  also  in  part  by  the  expense  connected  with 
the  opening  of  new  quarries. 

372.  Voids  in  the  Broken  Stone. — The  voids  of  broken  stone  in 
which  the  size  and  shape  of  the  pieces  are  nearly  uniform  are  about 
one  half  the  mass.     If  the  pieces  are  not  uniform,  the  voids  are 
about  four  tenths  of  the  mass.    The  voids  in  gravel  vary,  but  aver- 
age about  one  half  of  the  mass.     The  greatest  amount  of  rolling 
will  not  reduce  the  voids  more  than  one  half  of  the  primitive  bulk. 


268 


HIGHWAY    CONSTRUCTION. 


TABLE  XXXIX. 
COST  OF  QUARRYING  AND  CRUSHING  STONE. 


Year. 

Cost  of 
Quarrying  per 
cubic  yard. 

Cost  of 
Crushing  per 
cubic  j'ard. 

Cost  of 
Carting  to 
Breaker  per 
cubic  yard. 

Total  Cost  of 
Crushed  Stone 
at  the  Quarry 
per  cubic  yard. 

Average  Cost 
Delivered  on 
the  Streets 
per  cubic  yard. 

1881  

.655  Ct. 

.536ct. 

.283ct. 

$1.47 

$1.70 

1882     .. 

.781  ct. 

.348  ct. 

.  237  ct. 

1.36 

.87 

1883  

.  638  ct. 

.265  ct. 

.247ct. 

1.15 

.59 

1884 

.665  ct. 

372  ct 

.  228  ct. 

1.26 

70 

1885  

.658ct. 

.342  ct. 

.  224  ct. 

1.23 

.66 

1886  

.  590  ct. 

.289  ct. 

.233ct. 

1.12 

.65 

1887  
1888  

.595  ct. 
658  ct. 

.345ct. 
.221  ct. 

.281ct. 
.  288  ct. 

1.22 
1.17 

.64 
.63 

1889  

.694ct. 

.319  ct. 

.  263  ct. 

1.28 

1.69 

1890  

.889  ct. 

.407ct. 

.  301  ct. 

1.597 

2.045 

A  well-rolled  road-covering  contains  from  70  to  80  per  cent  of 
stone. 

373.  Determination  of  the  Voids  in  Broken  Stone. — The  pro- 
portion of  voids  may  be  determined  by  experiment  in  either  of  the 
following  ways :  (1)  Determine  the  specific  gravity  of  the  material, 
and  from  that  the  weight  of  a  unit  of  volume  of  the  solid.     Weigh 
a  unit  of  volume  of  the  loose  material.     The  difference  between  the 
weights   divided   by  the  first  gives  the  proportion  of  the  voids. 
(2)  Wet  the  loose  material  thoroughly,  fill  a  vessel  of  known  capac- 
ity with  it,  and  then  pour  in  all  the  water  the  vessel  will  contain. 
Measure  the  volume  of  water  required   and   divide   this  by  the 
volume  of  the  vessel;   the  quotient  represents  the  proportion  of 
voids. 

The  smaller  the  stone  is  broken  the  less  the  percentage  of  voids 
and  the  heavier  a  cubic  yard  will  weigh. 

374.  Weight  of  Broken  Stone. — To  ascertain  the  weight  of  a 
cubic  yard   of  broken   stone,    multiply   the   weight   of   a  cubic 
yard  of  the  given  stone  by  the  proportion  of  voids  (usually  0.50) ; 
the  result  will  be  the  weight  of  a  cubic  yard  of  the  stone  when 
broken. 

375.  Area  covered  by  One   Cubic  Yard  of  Broken  Stone. — A 
cubic  yard  of  ordinary  broken  stone  will,  when  properly  spread, 
cover  an  area  of  about  32  square  yards  of  surface  of  a  roadway. 

Since  a  cubic  yard  of  loose  broken  stone  contains  only  one  half 


BROKEN-STONE    PAVEMENTS.          »  269 


of  its  volume,  or  13£  cubic  feet  of  solid  stone,  its  weight,  allowing 
12  cubic  feet  of  solid  granite  to  one  ton,  is  approximately 


=  1  ton. 


Again,  one  cubic  yard  is  equivalent  to  36  square  yards  1  inch  deep; 
and  1  ton  of  stone  laid  without  compression  to  a  depth  of  1  inch 

-covers  an  area  of  36  X  --—  =  32  square  yards.     When  the  stone  is 

•l-ff 

laid  and  rolled  the  primitive  volume  is  reduced  by  about  one  fourth; 
and  1  ton  of  rolled  stone  laid  to  a  depth  of  one  inch  covers  an  area 
one  fourth  less  than  32,  or  32  X  f  =  24  square  yards. 

376.  To  Find  the  Area  that  can  be  covered  by  One  Ton  of  Stone, 
when  the  Thickness  of  the  Layer  is  given.  —  Divide  32  by  the  thick- 
ness of  the  layer  in  inches  if  unrolled  ;  or  divide  24  by  the  thick- 
ness of  the  layer  in  inches  when  rolled.     The  quotient  is  the  area 
in  square  yards. 

377.  To  Find  the  Area  that  can  be  covered  by  One  Cubic  Yard 
of  Broken  Stone,  when  the  Thickness  of  the  Layer  is  given.  —  When 
the  stone  is  not  rolled,  divide  36  by  the  thickness  in  inches;  the 
quotient  is  the  number  of  square  yards  that  can  be  covered.    When 
the  stone  is  rolled,  divide  27  by  the  final  thickness  in  inches;  the 
quotient  is  the  number  of  square  yards. 

378.  Thickness  of  the  Broken  Stone.  —  The  offices  of  the  stone 
are  to  endure  friction  and  shed  water;  its  thickness  must  therefore 
be  regulated  by  the  quality  of  the  material  and  the  amount  of  the 
traffic,  and  not  by  any  consideration  as  to  its  own  independent 
power  of  bearing  weight.     Macadam  considered  10  inches  as  suffi- 
cient for  any  traffic  on  any  substratum:  experience  has  proved  this 
true  in  the  well-drained  and  well-kept  roads  of  Europe. 

379.  The  proper  rule  is  to  vary  the  thickness  according  to  the 
traffic  and  the  grade.  Eoads  of  sharp  descent  do  not  require  as 
thick  covering  as  those  having  flat  grades. 

Mr.    J.    Owen,   County  Engineer    of    Essex    County,  N.  J., 
adopted  the  following  thicknesses  with  good  results  : 

For  grades  flatter  than  \%  ...............................  10  inches 

between  \%  and  4%  ........  .  ..................     8      " 

........  ,  ............................     6     " 


270  "  HIGHWAY    CONSTRUCTION". 

The  roads  of  Bridgeport,  Conn,  (upwards  of  50  miles),  built 
under  the  direction  of  Mr.  B.  D.  Pierce,  are,  with  the  exception  of 
two  short  pieces,  only  4  inches  thick.  These  roads  are  subjected  to  a 
regular  traffic  of  loads  averaging  6000  pounds  each;  they  give  entire 
satisfaction  to  the  public  using  them,  and  an  ordinary  team  hauls  a- 
net  load  of  3000  pounds  over  them. 

380.  Many  roads  of  4  and  6  inches  thickness  have  been  built  that 
have  not  proved  satisfactory.     Their  failure  is  generally  attributed 
to  their  thinness.    This  is  erroneous ;  the  fault  does  not  always  lie  in 
the  thinness  of  the  stone  covering,  but  in  the  method  of  construc- 
tion followed.     The   thin   roads  that  fail  are  as  a  rule  made  by 
throwing  the  broken  stone  on  an  undrained  and  unrolled  earth 
roadway,  frequently  without  even  removing  the  mud  which  covers 
its  surface.     In  some  few  cases  the  stones  are  rolled  with  a  horse 
roller,  but  in  the  majority  the  stone  is  left  to  be  consolidated  by 
the  traffic.     If  roads  are  to  be  built  in  this  manner,  they  must  be 
massive ;   but   no   matter  how  massive   they   be  made,  they  will 
have  no  cohesive  strength,  they  will  never  be  impervious  to  the 
rnud  from  below  or  the  rain  from  above,  and  will  always  be  unsatis- 
factory. 

381.  Sand  Core  for  Broken-stone  Pavement. — On  a  well-drained 
foundation  a  sand  or  gravel  core  will  be  found  as  mechanically 
serviceable  as  the  most  costly  stone  foundation.    Such  a  core  covered 
with  a  layer  of  stone  measuring  when  compacted  4  inches  thick 
will  form  a  finer  and  more  lasting  surface  than  a  greater  thickness 
of  stone  laid  upon  the  earth  soil  and   compacted.     Telford  was 
aware  of  this  fact ;  he  was  willing  to  prevent  by  almost  any  means 
available  the  coming  in  contact  of  his  road  material  with  the  earth 
subsoil,  and  suggested   gravel,  sand,  or  chalk   as  alternatives  to 
bottoming  stones.   A  requisite,  whatever  the  medium,  was  that  "  this 
bottoming  should  be  made  perfectly  firm  and  regular,  so  as  to  re- 
ceive the  top  workable  metal  of  equal  thickness."      Thus,  although 
he  always  advised  a  paved  bottom  when  it  could  be  had,  many  miles 
of  roadway  were  made  under  Telford's  direction  without  the  paved 
bottom  with  which  his  name  is  associated. 

382.  The  quantity  of  broken  stone  required  per  mile  of  road  for 
different  widths  and  thicknesses  is  given  in  Table  XL. 

383.  Spreading  the  Stone. — The  stone  should  be  hauled  upon 
the  roadbed  in  broad-tired  two-wheeled  carts  and  dumped  in  hepps, 


BROKEN-STONE    PAVEMENTS. 


271 


TABLE  XL. 

NUMBER  OP  CUBIC   YARDS   OF   BROKEN   STONE   REQUIRED  PER  MILE  OF 

ROAD. 


Depth  of 
Stone  in 
Inches. 

vviuixi  UL  ravemeni  in  reet. 

8               16 

i 

24 

30 

32 

10                   48 

60 

4 

645 

1,290 

1,935 

2,421 

2,580 

3,225 

3,870 

4,842 

6 

968 

1,935 

2,903 

3,632 

3,872 

4.840 

5,808 

7,264 

t/8  - 

1,290 

2,580 

3,870 

4,842 

5,160  1       6,450 

7,740 

.    9,684 

10 

1,613 

3,225 

4,838 

6,053 

6,452 

8.065 

9,678 

12,106 

12 

1,935 

3,870 

5,805 

7,263 

7,740 

9,675 

11,610 

14,526 

14 

2,258 

4,515 

6,773 

8,474 

9,032 

11,290 

13,548 

16,948 

16 

2,580 

5,160 

7,740 

9,684 

10,320 

12,900 

15,480 

19,368 

and  be  spread  evenly  with  a  rake  in  a  layer  of  as  nearly  uniform 
thickness  as  may  be. 

384.  Thickness  of  the  Layers.— The  thickness  of  the  layers  will 
depend  upon  the  final  thickness  of  the  covering.     If  the  finished 
thickness  is  to  be  6  inches,  each  layer  should  be  of  a  depth  of  4£ 
inches. 

385.  Macadam  insisted  that  the  stone  should  not  be  laid  in 
shovelfuls  but  scattered  over  the  surface,  one  shovelful  following 
another  and  spreading  over  considerable  space.     His  object  in  this 
was  to  avoid  an  accumulation  of  soft  stones  at  one  spot,  for  the 
rocks  from  which  the  stone  was  obtained  were  not  of  uniform  hard- 
ness, but  of   all   qualities   gathered   from   adjoining   fields.      The 
application  of  this  method  to  stone  of  uniform  quality  would  be 
detrimental  and  have  the  same  effect  as  screening. 

386.  Binding. — One  half  of  the  volume  of  loosely  spread  broken 
stone  is  space,  and  no  amount  of  rolling  will  reduce  it  more  than 
one  half;  therefore  to  thoroughly  consolidate  the  broken  stone  some 
fine  material  must  be  added.     It  may  consist  of  the  fragments  and 
detritus  obtained  in  crushing  the  stone.    When  this  is  insufficient,  as 
will  be  the  case  with  the  harder  rocks,  the  deficiency  may  be  made 
up  of  clean  sand  or  gravel.    The  proportion  of  binder  should  slightly 
exceed  the  voids  in  the  aggregate;  it  must  not  be  mixed  with  the 
stones,  but  should  be  spread  uniformly  in  small  quantities  over  the 
surface  and  rolled   into  the  interstices  with  the  aid  of  water  and 
brooms. 


272  HIGHWAY    CONSTRUCTION. 

387.  It  is  a  useless  refinement  to  screen  the  broken  stone;  it 
should  be  placed  in  the  road  as  it  comes  from  the  breakers,  care  be- 
ing taken  to  prevent  the  admixture  of  clay  or  loam,  the  presence  of 
which  in  large  quantities  is  extremely  injurious.     When  present  to 
an  injurious  extent,  the  stone  must  be  screened. 

388.  By  using  a  large  quantity  of  binding  material  mixed  with 
the  stones  the  amount  of  rolling  is  lessened,  but  at  the  expense  ol 
durability.     If  there  is  an  excess  of  binding  material  in  the  joints 
of  the  stones,  the  first  .heavy  rain  washes  it  out  and  the  surface  of 
the  roadway  quickly  goes  to  pieces. 

389.  The  French  engineers  use  clay,  sand,  or  earth  from  the 
road  excavation  when  such  is  suitable,  in  the  proportion  of  one 
fourth  to  one  sixteenth  of  the  bulk  of  the  stone.     They  apply  it 
after  the  steam  roller  has  been  once  over  the  broken  stones. 

390.  Necessity  of  Binding  Material. — Wi'th  reference   to  the 
necessity  of  binding  material,  the  following  facts  are  interesting. 

Mr.  Wm.  H.  Grant,  Superintending  Engineer  of  the  New  York 
Central  Park,  in  his  report  upon  the  park  roads,  says: 

"  At  the  commencement  of  the  macadam  roads,  the  experiment 
was  tried  of  rolling  and  compacting  the  stone  by  a  strict  adherence 
to  Macadam's  theory,  that  of  carefully  excluding  all  dirt  and  foreign 
material  from  the  stones,  and  trusting  to  the  action  of  the  roller 
and  the  travel  of  teams  to  accomplish  the  work  of  consolidation. 
The  bottom  layer  of  stone  was  sufficiently  compacted  in  this  way 
to  form  and  retain,  under  the  action  of  the  rollers  (after  the  com- 
pression had  reached  its  practical  limit),  an  even  and  regular  sur- 
face; but  the  top  layer,  with  the  use  of  the  heavy  roller  loaded  to 
its  greatest  capacity,  it  was  found  impracticable  to  solidify  and 
reduce  to  such  a  surface  as  would  prevent  the  stones  from  loosening 
and  being  displaced  by  the  action  of  wagon-wheels  and  horses'  feet. 
No  amount  of  rolling  was  sufficient  to  produce  a  thorough  binding 
upon  the  stones,  or  to  cause  a  mechanical  union  and  adjustment  of 
their  sides  and  angles  together  as  to  enable  them  mutually  to  assist 
each  other  in  resisting  displacement.  The  rolling  was  persisted  in 
with  the  roller  adjusted  to  .different  weights  up  to  the  maximum 
load  (12  tons),  until  it  was  apparent  that  the  opposite  effect  from 
that  intended  was  being  produced.  The  stones  became  rounded  by 
the  excessive  attrition  they  were  subjected  to,  their  more  angular 
parts  wearing  away,  and  the  weaker  and  smaller  ones  being  crushed. 


BROKEN-STONE    PAVEMENTS.  273 

"  The  experiment  was  not  pushed  beyond  this  point.  It  was 
conclusively  shown  that  broken  stones  of  the  ordinary  sizes  and  of 
the  best  quality  for  wear  and  durability,  with  the  greatest  care  and 
attention  to  all  the  necessary  conditions  of  rolling  and  compression 
would  not  consolidate  in  the  effectual  manner  required  for  the  sur- 
face of  a  road  while  entirely  isolated  from  and  independent  of 
other  substances.  The  utmost  efforts  to  compress  and  solidify  them 
while  in  this  condition,  after  a  certain  limit  had  been  reached,  were 
unavailing." 

391.  Mr.  Deacon,  Engineer  of  Liverpool,  England,  describes  the 
effect  of  binding  material  as  follows: 

"  Under  a  15-ton  steam  roller  preceded  by  a  watering-cart,  1200 
yards  of  trap-rock  macadam,  without  binding,  can  only  be  moder- 
ately consolidated  by  twenty-seven  hours'  continuous  rolling.  If 
the  trap-rock  chippings  from  the  stone-breaker  are  used  for  binding, 
the  same  area  may  be  moderately  consolidated  by  the  same  roller  in 
eighteen  hours.  If  silicious  gravel  from  f  inch  to  the  size  of  a 
pin's  head,  mixed  with  about  one  fourth  part  of  macadam  sweepings 
obtained  in  wet  weather,  be  used,  the  area  may  be  thoroughly  con- 
solidated in  nine  hours. 

v  Macadam  laid  according  to  the  last  method  wears  better  than 
that  laid  by  the  second,  and  that  laid  by  the  second  much  better 
than  that  laid  by  the  first." 

392.  Watering. — Wetting  the  stone  expedites  the  consolidation, 
decreases  crushing  under  the  roller,  and  assists  the  filling  of  the 
voids  with  the  binder.    It  should  be  applied  by  a  sprinkler  and  not 
be  thrown  on  in  quantity  or  from  the  plain  nozzle  of  a  hose. 

Excessive  watering,  especially  in  the  earlier  stages,  tends  to  soften 
the  foundation,  and  care  should  be  exercised  in  its  application. 

393.  Compacting  the  Broken  Stone. — Three  methods  of  com- 
pacting the  broken  stone  are  practised :  (1)  by  the  traffic  passing 
over  the  road;  (2)  by  rollers  drawn  by  horses;  (3)  by  rollers  pro- 
pelled by  steam. 

391.  The  first  method  is  both  defective  and  objectionable. 
(1)  It  is  destructive  to  the  horses  and  vehicles  using  the  road.  (2) 
It  is  wasteful  of  material;  about  one  third  of  the  stone  is  worn  away 
in  the  operation.  (3)  Dung  and  dust  are  ground  up  with  the  stone, 
and  the  road  is  more  readily  affected  by  wet  and  frost. 

395.  The  first  recorded  allusion  to  the  consolidation  of  roads 


274  HIGHWAY   CONSTRUCTION. 

by  rolling  seems  to  have  been  made  in  1619  by  John  Shotbolt  m 
England.  The  first  practical  application  of  rollers  appears  to  have 
been  made  by  the  French  engineers  in  1829.  Their  first  applica- 
tion in  England  appears  to  have  been  made  by  Sir  John  E.  Bur- 
goyne.  Since  these  dates  rolling  has  been  universally  adopted  on 
the  continent  of  Europe,  not  as  a  refinement  but  as  a  necessity,  and 
no  road  is  considered  complete  until  it  has  been  thoroughly  com- 
pacted by  a  roller. 

396.  Advantages  of  Rolling. — The  advantage  of  rolling  broken- 
stone  pavement  may  be  summed  up  as  follows  : 

(1)  The  saving  of  wear  and  tear  of  horses  and  vehicles.     Roads 
should  be  made  for  the  traffic  and  not  by  it. 

(2)  Comfort  of  persons  using  the  roads. 

(3)  Economy,  as  a  saving  of  from  30  to  50  per  cent  is  effected 
by  reason  of  the  roads  being  better  made,  thus  obviating  the  neces- 
sity for  such  frequent  sweeping  and  scraping.     If  a  portion  of  a 
road  that  has  not  been  rolled  is  broken  up  and  the  material  washed, 
it  will  be  found  that  as  much  as  half  of  it  is  soluble  matter,  mud, 
dirt,  and  fine  sand.     The  stones  having  been  thrown  loosely  upon 
the  road-bed  have  lain  so  long  before  becoming  consolidated  by  the 
traffic,  and  have  undergone  in  the  mean  time  such  extensive  abra- 
sion, that  the  proportion  of  mud,  dirt,  and  pulverized  material  is 
increased  to  that  extent,  and  the  stones  are  really  only  stuck  to- 
gether by  the  mud.     This  accounts  for  the  fact  that  although  an 
unrolled  road  may  indeed  after  long  use  have  a  surface  that  is 
pretty  good  and  hard  in  dry  weather,  and  may  offer  then  a  very 
slight  resistance  to  traction,  yet  it  will  quickly  become  soft  and 
muddy  when  there  is  rain.     By  the  employment  of  a  roller  of  com- 
petent weight  the  stones  are  well  bedded  at  once,  and  the  surface  is? 
consolidated  into  a  sort  of  stone  felt  capable  of  resisting  most  effect- 
ually the  action  of  the  traffic,  and  containing  the  smallest  quantity 
of  soluble  matter  to  form  mud  in  wet  weather. 

(4)  The  avoidance  of  cruelty  to  horses,  as  in  the  case  of  newly 
metalled  unrolled  roads. 

397.  Horse-rollers.* — Rollers    drawn  by    horses  are  unsatisfac- 

*Mauy  improvements  have  been  made  in  the  construction  of  horse-rollers 
during  the  past  few  years,  such  as  the  use  of  hollow  iron  cylinders,  which  may 
be  weighted  by  water  or  sand,  and  the  rotary  table,  which  renders  no  longer- 
necessary  the  difficult  task  of  turning  the  roller  bodily,  and  avoids  the  plough- 
ing up  of  a  portion  of  the  newly  rolled  stone. 


BROKEN-STONE    PAVEMENTS.  275 

tory  for  compacting  the  broken  stone.  They  are  expensive  to  use, 
requiring  a  large  number  of  horses  and  attendants.  The  horses* 
feet  displace  as  many  stones  as  the  roller  compacts,  and  if  they  are 
of  great  weight  they  become  clumsy  and  difficult  of  manipula- 
tion. 

398.  Steam   Rollers. — Steam   rollers   were   first   introduced   in 
1860,  since  which  time  they  have  been  almost  universally  adopted 
on  account  of  the  superiority  and  economy  of  the  work  done.    They 
are  simply  a  locomotive  mounted  on  broad  and  heavy  wheels.    They 
can  be  made  of  any  desired  weight.    Those  now  in  use  vary  from  three 
to  thirty  tons.     Ten  tons  appears  to  be  the  most  desirable  weight. 
Heavier  rollers  are  unwieldy,  and  from  their  great  weight  are  liable 
to  damage  the  sewers,  water,  or  other  underground  service-pipes 
that  may  be  in  the  roadway. 

399.  The  advantages  of  steam  rolling  may  be  summed  up  as 
follows : 

(1)  They  shorten  the  time  of  construction. 

(2)  A  saving  of  road  metal,  (a)  because  there  are  no  loose  stones 
to  be  kicked  about  and  worn;  (b)  because  there  is  no  abrasion  of 
the  stones,  only  one  surface  of  the  stone  being  exposed  to  wear; 
(c)  because  a  thinner  coating  of  stone  can  be  employed ;  (d)  because 
no  ruts  can  be  formed  in  which  water  can  lie  to  rot  the  stone. 

(3)  Steam-rolled  roads  are  easier  to  travel  on  account  of  their 
even  surface  and  superior  hardness  and  have  a  better  appearance. 

(4)  The  roads  can  be  repaired  at  any  season  of  the  year. 

(5)  Saving  both  in  materials  and  manual  labor. 

400.  Form  of  Rollers. — The  advantage  of  the  present  form  of 
rollers  is  generally  overestimated.     The  heaviest  roller  in  use  does 
not  exert  the  same  pressure  per  inch  of  width  nor  in  the  same  man- 
ner that  a  heavily  loaded  wagon  does,  but  the  demand  that  a  roller 
should  be  as  heavy  per  inch  of  width  as  a  loaded  wagon-wheel  is 
per  inch  of  tire  cannot  be  successfully  met. 

The  wheels  of  the  rollers  now  in  use  have  too  wide  a  bearing  on 
the  road  surface.  The  smaller  soft  spots  are  bridged  over  and  remain 
unseen  until  the  road  is  completed  and  thrown  open  for  use.  The 
traffic  will  quickly  find  these  soft  spots,  and  hollows  and  ruts  will 
form.  To  obviate  this  and  obtain  the  best  effect  from  rollers,  they 
should  be  constructed  with  both  front  and  rear  rolls.  The  front  roll 
should  be  formed  of  disks,  having  diameters  varying  about  six  inches, 


276  HIGHWAY    CONSTRUCTION. 

set  alternately  on  the  axle.  The  rear  roll  may  be  formed  of  two  or 
more  disks  of  uniform  diameter.  The  ridges  left  by  the  front  roll 
will  be  levelled  by  the  rear  roll.  The  effect  produced  by  a  roller  of 
this  form  will  approximate  more  nearly  the  effect  of  loaded  wagon- 
wheels. 

401.  The  driving  rolls  of  steam-rollers  usually  have  holes  bored 
in  their  faces  to  receive  spikes,  in  order  that  they  may  be  used  for 
breaking  up  or  disintegrating  the  road-surface.     These,  however, 
apparently  do  not  answer;  the  working  of  a  machine  in  this  man- 
ner shakes  and  strains  it  considerably,  and  the  holes  in  the  rollers, 
which  are  plugged  with  wood  when  not  in  use  for  this  purpose,  are 
objectionable;  the  plugs  wear  out  and  the  road  metal  gets  into 
holes,  and  the  surface  of  the  road  is  picked  up  as  the  rolling  pro- 
ceeds.    Besides  this,  the  spikes  seem  to  have  no  effect  unless  the 
surface  of  the  roadway  being  operated  upon  is  soft. 

402.  The  steepest  gradient  upon  which  a  steam  roller  can  be 
operated  appears  to  be  1  in  6,  but  this  requires  a  very  heavy  pres- 
sure of  steam;  1  in  14  or  about  7fo  seems  to  give  no  trouble  in 
rolling  either  up  or  down. 

403.  Cost  of  Maintaining  Steam  Rollers. — The  annual  cost  of 
maintaining  steam  rollers  as  given  in  the  reports  of  city  engineers 
is, as  follows: 

HARTFORD,  CONN. 

One  10-ton  roller $4,000.00 

Wages  of  engineer  aud  tenders $888.57 

€oal  (40,730  pounds) 1 1 1 . 01 

Wood  (54-  cords) 31.20 

Water  for  boiler 12.00 

Repairs,  tools,  etc 210.70 

Oil,  waste,  and  packing , 43.59 

Insurance 15.00 

Total  for  year $1,312.07 

TOLEDO,  OHIO. 

Wages $951 . 50 

Fuel,  supplies,  and  repairs 316.29 

Total  for  year $1,267.79 

DULUTH,  MINN. 
j,  fuel,  repairs,  etc $2,087.41 


BROKEN-STONE    PAVEMENTS.  277 

In  England  the  cost  per  annum  for  9  hours  per  day  is  aboufr 
$2000. 

404.  Amount  of  Rolling.— The  number  of  superficial  yards 
rolled  per  day  must  vary  extremely  with  circumstances — the  class 
of  material,  the  amount  of  binding  and  water  used',  the  gradient  and 
pressure  of  steam  maintained,,  and  the  amount  of  rolling  considered 
necessary.  The  number  of  square  yards  rolled  varies  from  500  to 
3000  per  diem,  the  average  of  42  English  towns  being  1105  square 
yards  per  diem. 

In  Paris  2  to  3.75  ton-miles  of  roller  are  applied  to  every  cubie 
yard  of  stone.  The  weight  of  steam  rollers  per  inch  of  run  is  speci- 
fied to  be  448  and  336  pounds,  and  for  horse  rollers  263  pounds. 
The  ton-miles  necessary  to  make  a  square  yard  of  porphyry  wheel- 
way,  or  to  compact  a  cubic  yard  of  the  same  metal,  is  given  as 
follows:  The  mean  for  two  models  of  machines  weighing  448 
pounds  per  inch  run  was,  per  square  yard,  with  the  thickness  of 
3.9  inches,  0.41  ton-mile;  while  for  the  roller  of  336  pounds,  with 
a  thickness  of  2.8  inches,  0.234  ton-mile  was  required,  or  3.78  and 
2.99  ton-miles  per  cubic  yard  respectively;  and  for  horse  rollers, 
where  the  thickness  was  2.6  inches,  the  ton-miles  required  were 
0.194  per  square  yard  and  2.69  per  cubic  yard.  The  amounts  con- 
solidated per  ton  per  hour  are  in  the  following  proportions:  467  for 
the  heavy  rollers,  539  for  the  light  rollers,  and  297  for  the  horse 
roller,  and  the  number  of  passages  of  the  rollers  were  98.5,  75,  and 
92.  The  maximum  speed  is  stated  at  2.3  miles  per  hour.  The  roll- 
ing is  done  by  contract  (the  city  furnishing  the  water)  at  a  rate 
per  ton-mile  varying  from  15.26  to  7.63  cents,  according  to  the 
amount,  with  an  increase  of  one  third  in  price  where  the  grade 
exceeds  6  per  cent. 

The  Southern  Boulevard,  New  York  City,  constructed  by  Mr. 
E.  P.  North,  received  0.859  ton-mile  per  square  yard  or  5.177  ton- 
miles  per  cubic  yard. 

From  careful  experiments  with  blue  limestone  in  England,  it 
has  been  found  that  to  obtain  consolidation  with  the  usual  coating 
of  two  stones  in  thickness  (each  cubic  yard  broken  to  2|-inch 
gauge,  and  made  to  cover  about  17  square  yards  of  surface),  the 
steam  roller  must  traverse  a  patch  equal  to  its  own  width  about 
35  times.  From  this  it  appears  that  a  cubic  yard  of  broken  stone 
requires  1£  ton-miles  to  produce  consolidation.  For  binding  about 


278  HIGHWAY    CONSTRUCTION. 

5  per  cent  of  well-weathered  road  -scraping  was  used,  being  spread 
over  the  surface  when  consolidation  was  nearly  effected.  Without 
the  use  of  binding,  consolidation  was  found  impossible. 

The  only  guide  for  the  proper  amount  of  rolling  is  that  it  must 
be  continued  until  the  stones  cease  to  creep  in  front  or  sink  under 
the  rolls,  and  the  surface  has  become  smooth  and  firm. 

To  ascertain  the  number  of  ton-miles  per  square  yard  or  the 
number  of  passages  of  a  roller   of  given  weight,  the   following 
formula  (deduced  by  Prof.  C.  H.  Brown)  may  be  used  : 
Let  R  =  weight  of  roller  per  lineal  inch  in  pounds  ; 

P  =  number  of  passages  of  roller  over  a  given  spot  ; 
T  =  number  of  ton-miles  per  square  yard  ; 
36  =  inches  in  1  yard  ; 
1760  =  yards  in  a  mile  ; 
2240  =  pounds  in  1  ton. 


10951177 


405.  Manner  of  Applying  the  Roller.  —  The  stone  should  be 
spread  in  a  uniform  layer  4|  inches  thick.  This  depth  will  consoli- 
date better  than  either  thicker  or  thinner.  Commence  the  rolling 
at  the  edge  or  border  of  the  roadway;  move  up  along  this  edge  and 
return  on  the  other  in  such  manner  that  during  each  succeeding  trip 
the  edge  of  the  strip  previously  rolled  is  overlapped  while  covering 
a  strip  closer  to  the  middle  of  the  road.  The  trips  or  passages  of 
the  roller  should  proceed  in  this  manner  and  be  continued  until 
such  a  degree  of  firmness  is  attained  that  when  the  roller  passes 
over  the  centre  or  the  crown  of  the  road  its  weight,  which  tends  to 
spread  the  metal  or  make  it  work  off  towards  the  sides,  may  be  re- 
sisted by  the  consolidation. 

The  surface  of  a  well-constructed  broken-stone  road  should, 
after  being  rolled,  look  almost  like  an  encaustic  pavement. 

The  rolling  should  be  done  slowly,  as  nothing  is  gained  by  a 
rapid  motion;  the  fuel  consumption  being  considerably  increased 
without  any  advantage  to  the  work. 


BROKEN-STONE    PAVEMENTS.  279 

In  the  execution  of  rolling  it  is  an  important  advantage  to  be 
able  to  change,  within  considerable  limits,  the  weight  of  the  roller, 
because : 

1st.  The  newly  spread  stone  fragments  are  most  readily  fixed 
in  position  when  exposed  to  moderate  pressure  in  the  beginning; 
once  bedded,  they  should  be  rolled  under  maximum  pressure.  This 
has  the  convenience  that  the  movement  of  the  unballasted  roller 
requires  about  the  same  tractive  force  on  loose  road  metal  as  the 
ballasted  roller  on  the  more  compacted  surfacing. 

2d.  Experience  teaches  that  the  time  needed  for  finishing 
diminishes  with  the  increased  weight  of  rollers.  It  appears  that, 
with  average  road  metal,  a  pressure  of  the  unballasted  roller  of 
from  72  to  110  pounds  per  inch  and  of  from  370  to  460  pounds  per 
inch  of  width  of  ballasted  roller  is  preferable. 

3d.  Not  only  the  character  of  the  broken  stone,  but  also  the 
resistance  of  the  substratum,  must  be  considered  in  the  selection  of 
roller  weight.  On  soft  or  wet  subsoil  heavy  rollers  will  cause  a  dis- 
tortion of  the  road-bed. 

In  order  to  secure  the  best  result,  the  rolling  should  be  com- 
menced with  a  roller  of  light  weight,  say  3  tons,  either  steam  or 
horse,  provided  with  hollow  cylinders  for  ballasting  with  sand  or 
water.  After  the  loose  fragments  have  been  crowded  together,  in- 
crease the  weight  by  means  of  ballast,  and  when  the  stones  near 
the  edges  have  been  compacted  so  that  there  is  no  noticeable  settle- 
ment, the  rolling  with  the  heaviest  roller  may  be  commenced  and 
continued  to  completion. 

The  following  rules  on  the  rolling  of  broken-stone  roads  are 
given  by  the  Massachusetts  Highway  Commission:. 

"  When  possible  roll  the  subgrade  with  a  steam-roller. 

"If  the  subgrade  is  too  sandy  to  roll,  cover  with  coarse  gravel 
laid  on  to  a  depth  of  three  inches,  or  as  much  more  as  may  be 
needed  to  give  a  good  foundation. 

"  Fill  any  depressions  with  the  same  material  until  the  surface 
is  true  and  even. 

"  All  broken  stone  must  be  rolled  in  screened  layers. 

"  After  spreading  the  first  course  of  broken  stone,  begin  rolling 
at  the  sides,  and  continue  thus  by  running  ahead  so  as  to  allow 
from  two  to  five  inches  of  the  driving-wheel  to  pass  over  the  shoul- 


280  HIGHWAY   CONSTRUCTION. 

'der,  and  backward  with  the  outer  edge  of  the  driving-wheel  from 
five  to  ten  inches  inside  the  edge  of  the  broken  stone.  Roll  until 
the  stone  ceases  to  '  wave  '  in  front  of  the  wheels,  and  until  it  seems 
firm  underfoot  as  you  walk  over  it.  Next  begin  on  the  other  side  and 
roll  in  the  same  manner.  Then  work  towards  the  centre  until  the 
stone  is  rolled.  Roll  each  layer  of  stone  in  the  same  manner. 

"  If  the  road  shows  a  wavy  motion  after  passing  the  roller  over 
it  three,  four,  or  more  times,  it  may  indicate  too  much  moisture  in 
the  subgrade.  If,  on  examination,  you  find  this  to  be  true,  stop  roll- 
ing and  move  ahead,  allowing  time  for  the  subgrade  to  dry  out. 

"  With  some  coarse,  hard  granite  rocks  it  has  been  noted  that 
after  the  roller  passes  over  them  a  few  times  they  begin  to  '  crawl/ 
and  the  sharp  edges  break  off.  A  slight  sprinkling  of  sand  or 
stone  screenings  or  water  may  prevent  this.  Try  one  after  another 
of  these  means  until  the  work  progresses  to  your  satisfaction.  You 
must  not  expect  to  prevent  the  stone  from  shaking  as  you  walk  over 
it,  but  you  need  to  continue  the  rolling  until  the  fragments  of 
stone  adjacent  to  where  the  foot  presses  do  not  move  as  you  walk. 
Most  of  the  rolling  must  be  done  before  you  spread  the  screenings. 
After  spreading  the  screenings,  water  and  roll  until  the  mud 
flushes  to  the  surface.  You  cannot  expect  to  prevent  the  stone 
from  kicking  out  if  the  teams  pass  over  the  road.  Keep  watch, 
and  in  a  few  days  have  the  roller  pass  once  or  twice  over  the  road, 
after  watering,  until  the  loose  stones  are  pressed  down  out  of  sight. 

"  Before  spreading  any  broken  stone,  great  care  must  be  taken 
to  have  the  subgrade  carefully  shaped  and  thoroughly  compacted. 

"All  shoulders  must  be  shaped  and  left  sufficiently  high  to  roll 
to  the  proper  grade  before  any  broken  stone  is  spread  on  the  road. 

"In  the  case  of  heavy  fills  you  must  not  run  the  roller  to  the 
edge  of  the  shoulders  unless  the  fill  has  had  time  to  settle.  Work 
out  slowly  on  this  kind  of  work. 

"In  every  case  the  screenings  used  on  the  surface  as  a  binder 
course  must  be  of  the  same  material  as  the  top  course  of  the  road. 

"  Excepting  where  it  may  be  needed  to  compact  hard  granite 
rocks,  as  before  referred  to,  you  will  use  water  only  on  the  top  or 
binder  course. 

"You  will  wet  this  binder  course  thoroughly  before  rolling,  but 
not  to  the  extent  of  saturating  the  foundation.  You  will  get 


BROKEN-STONE    PAVEMENTS. 


28  L 


better  results  and  prevent  the  screenings  from  being  picked  up  by 
the  wheels  of  the  roller  if  you  apply  water  and  allow  it  to  settle 
down  below  the  top  surface  before  passing  the  roller  over  it.  Too 
much  water  or  too  little  will  give  trouble  by  causing  the  surface  to 
be  picked  up. 

"You  must  not  under  any  conditions  roll  the  screening 
while  dry. 

"You  must  not  under  any  conditions  allow  teams  to  pass  over 
the  road  after  the  screenings  are  spread  and  before  they  are 
rolled." 

406.  Cost  of  Rolling. — The  average  cost  of  rolling  varies  con- 
siderably by  reason  of  the  amount  of  rolling  considered  necessary. 
In  England  it  varies  between  one  and  two  cents  per  square  yard. 
In  the  United  States  it  varies  between  0.015  to  14  cents  per  square 
yard. 

407.  Cost  of  Broken-stone  Pavement. — What  the  cost  of  broken- 
stone  pavements  will  be  must  depend  upon  the  accessibility  and 
cost  of  material  and  labor,  which  will  be  quite  variable.     In  Tables 
XLI  and  XLII  is  given  the  cost  in  different  localities  in  the  United 
States. 

TABLE   XLI. 
COST  OF  BROKEN- STONE  ROADS. 


Locality. 

Thickness 
of  Stone. 
Inches. 

Width  of 
Pavement. 
Feet. 

Method. 

Cost  per 
Mile. 

4 

18  to  20 

Macadam 

$3,000 

Fairtield  Conn    

4 

20 

Macadam 

5,000 

12 

16 

Telford 

9,530 

Franklin  Township,  N.  J.  .  . 
Kingston,  R.  I  

4 

8 

15 
16  to  20 

Macadam 
Macadam 

4,700 
5,500 

Linden  Township,  N.  J  
Plainfield   N  J 

12 

4  to  6 

16 
16 

Telford 
Macadam 

11,600 
3,000 

>     12 

16 

Telford 

9,349 

Westfield,  N.  J  

12 

16 

Telford 

9,640 

Union  Township,  N.  J  

12 

16 

Telford 

11,900 

282 


HIGHWAY   CONSTRUCTION". 


TABLE  XLII. 

EXTENT  AND  COST  OF  BROKEN-STONE  PAVEMENTS  IN  SOME  OF  THE 
PRINCIPAL  CITIES  OF  THE  UNITED  STATES  IN  1890. 


Cities. 


Extent. 
Miles. 


Cost  per  Square  Yard. 


St.  Louis,  Mo 271 . 76 

Chicago,  111 226.67 

Boston,  Mass... 172.00 

Nashville,  Teun '.  Ill .  00 

Providence,  R.  1 110.00 

Philadelphia,  Pa 90.80 

Hartford,  Conn 64.00 

Syracuse,  N.  Y 50.00 

Rochester,  N.  Y 46.00 

Patersou,  N.  J 38.00 

New  Haven,  Conn 28  50 

New  York,  N.  Y 25.34 

Worcester,  Mass 20.00 

Cambridge,  Mass 20.00 

Harrisburg,  Pa 20.00 

Toledo,  Ohio 10.39 

Burlington,  Vt 7.74 

Washington,  D.  C 6.00 

Richmond,  Va 5.72 

Utica,  N.  Y....C 2.62 

Oswego,  N .  Y 2.18 

Albany,  N.  Y 1.71 

Milwaukee,  Wis 1.16 

Los  Angeles,  Cal 1.00 

Scheuectady,  N.  Y 0.75 

Cincinnati,  Ohio 

Duluth,  Minn 44. 00 

Jersey  City,  N.  J 1 .50 

East  Saginaw,  Mich 1 .00 

Springfield,  Mass 15.00 

Chelsea,  Mass 5.00 

Dubuque,  Iowa 34.60 

Toronto,  Can 37 . 27 

Mobile,  Ala 20  00 

Lowell,  Mass 10.00 

St.  Louis,  Mo 18.33 

Newark,  N.  J 10.84 

Kingston,  N.  Y 4.50 

Toledo,  Ohio 1.11 

Trenton,  N.  J 0. 50 


$0.51 

0.90*tol.70t 
0.75   to  1.25 

0.45 


1.00 
0.69  to  1.08 

1.25 

0.45 

0.50  to  1.25 
1. 00  to  1. 501: 

0.70 
1.23 


0.75§ 

1.17 

1.251" 


0.84 
1.75 


*  Limestone  and  gravel  10  inches  deep. 
\  Telford.        §  12  inches  deep. 


f  Crushed  granite  topping. 
1"  18  inches  deep. 


407a.  Cost  of  Broken-stone  Roads  in  Massachusetts. — In  Massa- 
chusetts the  cost  of  State  highway  construction  under  the  contract 


BROKEN-STONE    PAVEMENTS. 


283 


system  has  ranged  from  $6600  to  $24,547  per  mile  and  has  aver- 
aged $10,033,  divided  as  follows: 

For  excavating  and  grading  .....  .......................  <M  241 

' 


"   Telford  and  drains  ...............................  3^7 

"   Macadam  and  shaping.  .  .........................  5,694 

"   Masonry  .........................  .  ...............  ^g 

"   Guard-rails  .......................................  igg 

"  Paved  gutters  .....................................  191 

•"  Engineering,  superintendence,  and  inspection  .......  679 

41  Minor  constructions,  catch-basins,  culverts  ..........  431 

•"   Stone  bounds  ....................................  54 

"  Advertising  .......   ..............................  ig 

"  Weighing  stone  ..................................  .  34 

"   Sundries  ..........................................  173 

Total  ............................................  $10,033 

408  Difference  in  the  Cost  of  European  and  American  Broken- 
stone  Pavements.  —  As  an  example  exhibiting  the  difference  in,  the 
•cost  of  constructing  macadam  roads  in  Europe  and  the  United 
States,  we  select  a  first-class  highway  of  the  broadest  type,  one 
which  was  built  about  ten  years  ago  over  a  level  expanse  between 
the  villages  of  Langenfeld  and  Burgwald,  Germany.  The  road  in 
question  is  2100  meters  (6888  feet)  long,  26|  feet  in  width,  the 
macadamized  wagon  track  13  \  feet  wide  and  8J  inches  thick.  With 
labor  estimated  at  36  cents  per  day  except  for  stone  masonry,  which 
-costs  in  country  districts  from  60  to  75  cents  per  day,  the  construc- 
tion account  of  this  road  foots  up  as  follows  : 


Germany. 

.America. 

$707.61 

$1748.00 

Planting  and  turfing  slopes  

89  96 

268.88 

!3ridge$  and  culverts    

154  70 

464.  10 

3647.35 

7843.50 

Milestones   etc           .     . 

11.38 

34.14 

Tools  

75.68 

151.36 

Damages  to  adjacent  property  during  work  .  .  . 

155.65 
61.88 

155.65 
185.64 

Superintendence  of  construction           

369.85 

784  35 

.Incidentals    

49.98 

49.98 

$5324.04 

14092.00 

$11680.00 
$8947.60 

per  mile 

per  mile 

284  HIGHWAY     CONSTRUCTION". 

409.  Wear  of  Broken-stone  Pavements. — The  wear  of  road  ma- 
terials resulting  in  their  gradual  reduction  to  detritus  is  due  to  the 
joint  action  of  the  traffic  and  the  weather.     When  the  wear  is  con- 
fined to  the  abrasion  of  the  surface,  it  is  the  least  possible;  but 
when  a  road  is  weak  from  insufficient  thickness,  or  from  a  yielding 
foundation,  bending  and  cross-breaking  take  place  under  passing 
loads,  and  a  movement  is  produced  in  the  body  of  the  road  which 
causes  internal  wear  by  the  rubbing  of  the  stones  against  each 
other;  this  wear  is  aggravated  by  the  softening  action  of  water 
finding  its  way  into  the  roadbed  through  cracks  in  the  surface,  and 
by  the  disintegrating  action  of  frost;  the  wear  and  waste  are  thus, 
far  greater  than  on  roads  of  sufficient  strength  properly  maintained, 

410.  The  relative  proportions  in  which  a  road  is  deteriorated  by 
the  action  of  atmospheric  changes,  wheels,  and  horses  feet  for  the 
generality  of  roads  is  approximately  as  follows : 

Atmospheric  causes 20    per'ceat 

Wheels *. 35.5     " 

Horses'  hoofs , 44.5     " 

411.  The  effect  of  horses'  feet  is  to  form  depressions  which,  if 
not  immediately  eradicated,  prepare  the  way  for  further  injury  by 
the  wheels.     Horses  moving  at  a  walk  and  drawing  heavily-loaded 
wagons  do  far  more  injury  than  horses  travelling  quickly  and  draw- 
ing lightly-loaded  vehicles. 

Rain. — The  effect  of  rain  upon  a  highway  is,  first,  to  soften  the 
bed,  and  next  to  wash  off  the  portion  of  the  material  which  the 
temporary  streams  can  bear  along.  On  an  earth  road  the  soften- 
ing action  is  highly  injurious,  as  it  permits  the  feet  of  animals  and 
the  wheels  of  vehicles  to  penetrate  below  the  surface.  On  a  prop- 
erly constructed  broken-stone  road,  as  well  as  on  all  forms  of  block 
pavement,  the  pavement  acts  as  a  roof,  shedding  the  water  from 
its  surface.  If  the  roadway  be  skilfully  planned,  the  penetration 
of  water  from  the  sides  is  avoided,  and  thus  the  damage  arising 
from  the  softening  action,  as  well  as  from  the  influence  of  frost,  is 
done  away  with.  On  all  forms  of  earth  roads,  and  on  the  most  of 
those  made  of  gravel  as  well,  the  effect  of  the  penetration  of  water 
in  loosening  the  mass  of  the  road-bed  is  serious,  in  most  cases  up  to 
the  margin  of  disaster. 

Where  a  hard  road  of  broken  stone  or  blocks  or  other  material 
impervious  to  water  is  properly  shaped,  the  rainfall  is  quickly 


BROKEN-STONE    PAVEMENTS.  285 

carried  to  the  side  ditches  by  the  arched  form  of  the  road.  On 
such  roads  the  water  never  courses  over  the  roadway  for  a  much 
greater  distance  than  its  width.  Thus  arranged,  the  streams,  even 
in  a  very  heavy  rainfall,  do  not  gain  much  volume  or  attain  great 
speed;  therefore  Ihsir  scouring  effect  is  but  small.  Nevertheless, 
the  storm-water,  by  removing  the  dust  from  the  roads  and  by 
washing  out  the  binding  material  between  the  stones,  hastens  the 
wearing  of  the  roadway.  This  is  especially  the  case  where  the 
broken  stone  is  of  the  softer  sort.  Where  the  pavement  is  com- 
posed of  the  basaltic  trap-rocks,  the  washing  influence  of  the 
waters  is  not  so  serious.  On  dirt  roads  the  rainfall,  especially 
after  times  of  frost,  is  the  most  serious  agent  of  destruction. 

The  power  of  water  to  move  and  transport  materials  depends 
upon  the  specific  gravity,  the  size  and  form  of  the  fragments,  and 
upon  the  velocity  of  the  water,  or,  what  amounts  to  the  same 
thing,  the  slope  of  the  roadway.  Hence  the  steeper  the  grade,  the 
greater  the  transporting  power  of  the  water,  and  the  longer  the 
distance  the  water  will  flow  over  the  roadway  before  it  is  dis- 
charged into  the  gutters  or  side  ditches. 

On  steep  grades  the  carrying  power  is  made  apparent  by  gullies; 
on  gentle  slopes  the  grains  of  the  least  weight  and  specific  gravity 
and  of  the  most  tabular  form  are  made  to  occupy  the  surface  of 
the  road,  where,  after  drying,  they  fall  an  easy  prey  to  the  power 
of  the  wind.  This  sorting  action  arises  from  the  fact  that,  other 
things  being  equal,  the  sand  grains  will  arrange  themselves  in 
water  in  the  order  of  their  specific  gravities,  the  heaviest  at  the 
bottom.  An  exception  to  this  rule  is  found  where  minerals  even 
of  a  high  specific  gravity  are  characteristically  of  a  tabular  form, 
since  the  resistance  they  offer  to  descent,  owing  to  their  relatively 
large  surfaces,  causes  them  to  arrange  themselves  at  the  top  with 
minerals  of  the  lowest  density. 

The  rain  falling  upon  a  road  serves  to  concentrate  the  minerals 
into  layers  in  the  order  of  their  specific  gravity.  This  will  not  be 
found  true  of  the  micas,  for  these  will  be  found  concentrated  near 
the  surface  with  the  minerals  of  a  less  density  and  both  made 
accessible  to  the  action  of  the  wind. 

The  impact  of  falling  rain-water  causes  a  certain  amount  of 
injury  by  attrition  and  loosening  of  those  grains  which  it  is  able  to 


286  HIGHWAY    CONSTRUCTION. 


move  about,  and  a  certain  weakening  of  the  coherency  of  the 
surface  as  far  down  as  the  water  is  able  to  penetrate. 

Frost. — The  immediate  effect  of  frost  action  on  a  broken- 
stone  road,  where  care  has  not  been  taken  to  keep  the  foundation 
dry,  is  to  heave  the  pavement  irregularly,  the  amount  of  the  up- 
lifting depending  on  the  quantity  of  water  which  has  become: 
frozen.  The  effect  of  this  irregular  motion  is  to  pull  the  cemented 
stones  apart,  and  sometimes  to  form  cracks  through  which  the 
water  can  penetrate.  Where  the  broken  stone  is  not  well  cemented, 
or  where  on  an  earth  or  gravel  there  are  stones  near  the  surface, 
the  effect  is  often  to  push  the  larger  fragments  upward  to  the  sur- 
face. It  may  in  general  be  said  that  all  frost  action  is  highly  detri- 
me"ntal  to  a  road,  and  that  therefore  the  utmost  care  to  exclude 
the  water  from  the  hardened  part  of  the  way,  as  well  as  from  the 
under  earth,  needs  be  taken. 

When  the  frost  enters  the  ground  the  first  effect  is  to  convert 
into  ice  the  water  within  the  zone  of  its  influence.  In  undergoing 
this  change  the  fluid  expands  to  the  amount  of  about  one-ninth  of 
its  bulk.  The  energy  with  which  this  expansion  occurs  is  in  all 
cases  sufficient  to  thrust  about  the  materials  of  the  soil.  So  long 
as  the  road  permits  water  to  pass  into  it,  and  wherever  ground- 
water  can  penetrate  from  the  sides  beneath  a  roadway,  however 
well  compacted,  even  if  it  be  quite  water-proof,  the  action  of  frost 
is  destructive. 

The  presence  of  frost  in  stones  is  promotive  of  weakness  and 
rapid  crumbling.  In  fragments  of  broken  stone  it  operates  to- 
increase  their  brittleness  to  a  considerable  degree,  and  for  this 
reason  gives  rise  to  a  more  rapid  disintegration  of  the  screenings 
and  upper  portion  of  the  road. 

Wind. — The  action  of  wind  on  roads  of  all  descriptions  is  con- 
siderable. The  effect  is  to  remove  all  the  loose  material  of  a  fine- 
grained nature  as  soon  as  it  becomes  dry.  On  earth  roads  and 
those  of  gravel  the  wearing  action  thus  accomplished,  though  it 
takes  place  in  a  more  even  way,  and  therefore  is  less  conspicuous, 
is  often  as  great  as  that  brought. about  by  the  rain.  On  broken- 
stone  roads  the  effect  is  considerable,  but  on  the  whole  not  seri- 
ously damaging,  except  where  the  pavement  is  made  of  rocks 
which  easily  powder,  such  as  limestone  and  slate.  The  diabase 


BROKEN-STOXE    PAVEMENTS.  287 

rocks,  which  carry  a  considerable  percentage  of  black  mica,  and 
the  mineral  feldspar,  which  decomposes  to  clay,  also  furnish  abun- 
dant material  for  the  wind's  work. 

The  sorting  action  of  the  wind  tends  to  remove  the  minerals 
having  the  least  specific  gravity,  and  this  will  be  particularly  true 
when  the  grains  possessing  the  least  density  happen  to  coincide 
with  those  of  a  brittle  nature,  and  which  for  this  reason  are  most 
liable  to  be  ground  to  a  condition  of  fine  dust  under  the  action  of 
the  wheels. 

Wind-blown  material  is  not  only  objectionable,  since  it  increases 
the  cost  of  road  maintenance,  but  is  an  intolerable  nuisance  to  the 
users  of  the  road  and  adjacent  residents. 

The  ability  of  the  wind  to  take  up  and  bear  away  grains  of  any 
rock  depends  upon  several  factors.  These  in  the  order  of  their 
importance  are:  (1)  The  form  of  the  particles  subjected  to  the 
wind's  influence;  (2)  the  specific  gravity  and  size  of  the  individual 
grains;  and  (3)  their  accessibility  to  the  action  of  the  wind.  The 
form  of  the  grains  will  depend  upon  their  original  shape  in  the 
rock  and  that  which  they  may  be  induced  to  take  as  an  effect  of 
road  wear  or  as  a  result  of  chemical  change.  The  most  suitable 
stone  to  be  used  for  highways,  to  withstand  the  action  of  the  wind, 
is  one  whose  products  of  abrasion  are  of  a  high  but  uniform  specific 
gravity,  and  which  is  free  from  all  minerals  that  by  their  tabular 
form  are  prone  to  be  thus  transported. 

A  small  amount  of  dust  is  of  value  on  a  road,  acting  like  a 
cushion  to  protect  the  broken  stone  from  the  action  of  the  wheels 
and  the  animals'  feet.  The  value  of  this  dust-film  is  further  en- 
hanced by  a  small  quantity  of  moisture. 

Disintegration  *  and  Decomposition  of  Road  Materials  by  tlie 
Chemical  Action  of  Hie  Elements  and  Organic  and  Inorganic  Acids. 
— Rain-water  impregnated  with  carbonic  acid  alone  acts  as  a  slow 
solvent  on  all  the  common  minerals  occurring  in  the  stones  used 
for  road  covering,  attacking  even  quartz;  but  a  mixture  of  the  vari- 
ous acids,  organic  or  inorganic,  acts  more  rapidly.  The  organic 
acids  occurring  in  all  water  circulating  through  the  soil  in  fertile 
regions  are  carbonic,  humic,  crenic,  and  apocrenic.  Neur  cities 
we  must  add  to  the  organic  acids  those  derived  from  gas-plants 
*  See  foot-note,  p.  288. 


288  HIGHWAY   CONSTRUCTION. 

and  manufacturing  establishments.  These  acids  are  largely  nitric, 
sulphuric,  and  hydrochloric. 

The  injurious  effects  of  organic  and  inorganic  acids  on  road- 
stones  are  confined  for  the  most  part  to  rocks  containing  calcite  or 
dolomite,  minerals  which  they  readily  dissolve  and  carry  away. 

Shrinkage  of  the  Subgrade.* — A  road-bed  may  suffer  disruption 
by  shrinkage  of  the  subgrade.  It  has  been  determined  experi- 
mentally that  clay  shrinks  one  fifth  of  its  bulk  in  excessively  dry 
weather  and  increases  to  a  corresponding  degree  when  wet,  and 
that  silicious  sands  and  gravels  undergo  no  change  in  volume. 
From  this  it  follows  that  when  a  road  passes  over  a  clay  bed  which 
may  become  dessicated,  injurious  results  are  likely  to  follow,  par- 
ticularly at  a  point  where  the  clay  abuts  a  sand  substratum  which 
is  unaffected  by  weather  changes. 

Gravity  *  also  plays  an  important  part  in  the  work  done  by  run- 
ning water  and  falling  rain.  Through  its  operation  alone  there  is 
always  a  tendency  exercised  for  grains  and  fragments  of  rock  to 
work  down  the  slopes  towards  the  sides  of  the  road.  Under  some 
circumstances  the  effect  of  gravity  may  completely  destroy  a  road- 
bed. When  the  roadway  is  constructed  along  a  mountainside 
whose  soil  is  slowly  creeping  toward  the  valley,  the  cut  made 
necessary  for  the  roadway  is  often  sufficient  so  to  weaken  the  hold 
of  the  soil  as  to  precipitate  the  surface  of  the  country  down  the 
slope  as  a  landslide,  or  cause  a  slower  movement  which  in  the  end 
entails  a  long-continued  and  serious  expense  in  the  way  of  repairs. 
Such  movements  are  particularly  common  in  loose  materials  in 
countries  where  the  frost  penetrates  deeply  and  the  ground  be- 
comes soft  in  the  time  of  thawing.  Roads  may  also  be  destroyed 
by  avalanches  of  trees  and  stones  from  a  point  farther  up  the 
slope. 

Changes  of  Temperature  *  produce  expansions  and  contractions 
of  the  rock  forming  the  road-covering,  which  in  extreme  cases 
break  the  bond  holding  together  the  broken  stone  and  cause 
cracks  and  fissures. 


*  Abbreviated  from  "The  Geology  of  the  Common  Roads  of  the  United 
States,"  by  N.  S.  Shaler,  and  "  The  Forces  which  Operate  to  Destroy  Roads," 
by  C.  I.  Whittle. 


BROKEN-STONE    PAVEMENTS.  289 

412.  The  quantity  of  stone  worn  away  annually  from  the  sur- 
face of  roads  is  an  exceedingly  variable  quantity,  dependent  not 
only  upon  the  character  of  the  stone  and  the  quantity  of  the  traffic, 
but  also  upon  the  mode  of  maintaining  the  road.     Mud  is  an  ex- 
cellent  assistant   in   rapidly   grinding  down  the   surface.     Many 
attempts  have  been  made  to  measure  the  wear  on  roads,  but  no 
definite  conclusions  can  be  arrived  at. 

413.  The  wear  or  loss  of  thickness  on  some  of  the  heavily  trav- 
elled streets  of  London  and  Paris  has  been  as  much  as  four  inches 
per  annum.     In  Birmingham,  England,  the  macadam  streets  have 
worn  down  six  inches  in  one  year  under  a  traffic  of  2484  vehicles  in 
ten  hours. 

The  average  loss  of  thickness  on  the  European  roads  appears 
not  to  exceed  one  inch  per  year. 

414.  The  amount  of  material  used  annually  in  England  to  re- 
place the  wear  on  main  roads  varies  from  40  cubic  yards  per  mile 
in  the  country  districts  to  1000,  and  in  some  cases  to  1500  cubic 
yards  in  the  vicinity  of  large  towns.     The  general  average  appears 
to  be  from  70  to  80  cubic  yards  per  mile,  the  least  being  10  cubic 
yards  per  mile. 

The  average  annual  consumption  of  broken  stone  to  replace 
wear  in  France  and  Austria  appears  to  be  about  70  cubic  yards  per 
mile. 

415.  The  loss  of  thickness  by  wear  should  be  restored  annually 
by  spreading  coats  of  two  or  more  stones  thick  and  consolidating  it 
with  the  roller.     Before  applying  the  coating  the  surface  of  the 
road  should  be  broken  up  with  picks  in  cross-courses  about  4  inches 
apart;  the  depth  to  which  the  surface  is  broken  should  not  exceed 
2  inches.     Steam  rollers  are  furnished  with  picks  for  this  purpose, 
but  their  employment  is  not  satisfactory  or  advantageous ;  if  the 
spikes  are  short,  they  have  no  effect  on  the  road  unless  it  is  soft;  if 
thuy  are  long,  they  penetrate  the  body  of  the  road,  breaking  the 
bond,  and  leave  the  road  a  mass  of  loose  stones.    Besides  the  employ- 
ment of  the  roller  for  this  purpose  shakes  and  strains  it  consider- 
ably. 

416.  The  practice  of  spreading  the  new  coating  and  leaving  it 
to  be  consolidated  by  the  traffic  is  open  to  the  same  objections  as 
the  construction  of  unrolled  roads.     It  is  an  obstacle  instead  of  an 
aid  to  traffic. 


290  HIGHWAY   CONSTRUCTION. 

"When  the  stone  is  spread,  the  sooner  it  is  rolled  solid  the  better. 

417.  Kecoating  the  road  should  be  done  at  that  season  of  the 
year  which  will  interfere  the  least  with  the  movement  of  the  traffic. 
Wet  or  damp  weather  is  most  suitable,  but  when  water  is  obtainable 
it  may  be  done  at  any  season. 

41 7a.  Effect  of  Climate  on  Broken-stone  Roads. — Regarding  the 
effect  of  climate  on  broken-stone  roads,  Prof.  N.  S.  Shaler  says: 
"  As  a  roadway  is,  of  all  constructions,  the  most  exposed  to  the 
action  of  the  weather,  the  climate  of  the  district  in  which  it  lies- 
has  a  greater  effect  upon  it  than  upon  any  other  class  of  buildings. 
This  effect  is  exercised  by  the  rainfall,  changes  in  temperature,, 
and  the  winds.  A  secondary  influence  arising  from  the  above- 
mentioned  natural  conditions  is  found  in  the  character  of  the 
vegetation,  which,  under  favorable  conditions,  may  advantageously 
affect  a  road  by  covering  the  unused  portion  of  its  surface  with  a 
network  of  low-growing  plants,  such  as  the  grasses. 

"  In  a  moderately  humid  climate,  exempt  from  continuous 
summer  droughts,  creeping  plants,  nourished  by  the  dust  from  the 
roads,  which  in  most  cases  has  a  considerable  fertilizing  value,  take 
hold  on  the  shoulders  and  sides  of  the  way  in  such  a  manner  as  to 
protect  those  exposed  parts  from  washing  or  from  the  action  of  the 
winds.  When  these  conditions  prevail  it  is  generally  practicable 
to  build  a  relatively  narrow,  hardened  way  with  wide  shoulders  on 
either  side,  onto  which  the  passing  teams  can  turn  out,  finding 
there,  by  virtue  of  the  plant-covering,  a  surface  so  firm  that  it  will 
not  rut  from  an  occasional  passage  of  wheels.  If,  however,  the 
shoulders  are  overdry,  as  they  are  sure  to  become  in  an  enduring 
drought,  the  plants  are  killed  and  the  surface  is  left  exposed." 

418.  Cost  of  Maintenance. — The  cost  of  maintaining  broken- 
stone  pavements  varies  between  very  wide  limits.     A  road  with 
little  traffic,  well  drained,  and  exposed  to  the  sun  and  air,  with 
fairly  good  materials  at  hand,  can  be  kept  in  repair  at  a  very  small 
yearly  cost,  while  a  suburban  or  city  street  may  cost  several  hun- 
dred dollars.     Unless  the  amount  of  the  traffic,  the  quantity  of  ma- 
terials used,  their  price,  and  other  particulars  be  taken  into  account, 
the  cost  per  mile  or  square  yard  at  which  a  road  is  maintained 
affords  little  real  information,  and  may  be  misleading. 

In  London  the  cost  of  maintaining  macadam  pavements  is 
stated  as  follows : 


BROKEN-STONE    PAVEMENTS.  291 

In  heavy-traffic  streets 62£  cts.  per  sq.  yd. 

In  moderate-traffic  streets 29£  " 

In  light-  '•          "     14fc 

In  lightest-       "          "     ...     6* 

In  Paris  macadam  costs  about  45  cents  per  square  yard  per 
year.  In  Boston,  Mass.,  about  50  cents. 

The  cost  of  maintaining  the  high-roads  of  Austria  ranges  from 
$1032  to  $1571  per  mile  per  annum;  of  these  amounts  about  50  per 
cent  (49  to  52)  is  for  materials.  The  highways  of  Belgium  cost  be- 
tween 6  and  10  cents  per  square  yard  per  year. 

The  French  roads  cost  from  1  to  10  cents  per  square  yard  per 
year. 

The  annual  cost  of  maintaining  the  government  roads  of  Bavaria 
in  1877  was,  per  kilometer,  or  .62  English  mile,  as  follows : 

Cost  of  material $54.26 

Extra  labor 11.42 

Bridges  and  culverts 2.  52 

Retaining-walls  and  gutters. . .        .31 

Road-paving 2.45 

Cost  of  tools..  1.02 


$71.98 

or  about  $116.09  per  English  mile.     Total  number  of  men  em- 
ployed on  the  government  roads  was  1089.     The  average  cost  of 
regular  roadmen  per  English  mile  was  $45.25. 
Total  length  of  government  roads : 

The  total  length  of  government  roads  macadamized 4,223  miles 

"       "        "        "          ."  "     paved 29     « 

"      "        "        "     .       "  "     over  bridges 6 

4,258  miles 

419.  Descriptions  of  Modern  Broken-stone  Roads. — "First-class 
metropolitan  roads,  England :  The  ground  is  excavated  or  filled  to 
the  required  level,  then  thoroughly  consolidated  by  rolling.  On  the 
earth-bed  thus  prepared  a  bottoming  or  bed  12  inches  thick,  of 
"  hard  core,"  consisting  of  brick  rubbish,  clinker,  old  broken  con- 
crete, broken  stone  or  shivers,  or  any  other  hard  material  in  pieces, 
is  spread  and  rolled  down  to  a  thickness  of  9  inches,  and  any  loose 
or  hollow  places  made  up  to  the  level. 


292  HIGHWAY   CONSTRUCTION. 

"  Next  comes  a  layer  of  Thames  ballast  5  inches  thick,  rolled 
solidly  to  a  thickness  of  3  inches.  The  ballast  serves  to  fill  up  the 
vacancies  in  the  bottoming,  and,  being  less  costly,  saves  so  much 
of  the  cost  for  broken  granite." 

Broken  granite,  or  macadam,  is  laid  upon  the  prepared  surface 
of  the  ballast  in  two  successive  layers  3  inches  thick,  rolled  succes- 
sively to  a  combined  thickness  of  4  inches;  a  layer  of  sharp  sand 
£  or  |  inch  thick  is  scattered  over  the  second  layer,  and  rolled 
into  it  with  plenty  of  water. 

420.  The  method  adopted  in  Chicago  is  as  follows :  The  roadbed 
is  prepared  to  the  required  contour  and  well  consolidated  with  a 
steam  roller.     On  this  surface  rubble-stone  is  carefully  placed  by 
hand,  with  its  broadest  side  downwards,  then  12  inches  of  broken 
stone  are  spread,  6  inches  at  a  time,  thoroughly  rolled;  to  bond  it ; 
it  is  then  topped  with  4  inches  of  crushed  trap  or  other  equally  hard 
rock;  this  is  again  thoroughly  rolled,  so  as  to  compact  and  bind  it 
together. 

421.  The  method  adopted  in  the  construction  of  the  Bridgeport, 
Conn.,  roads  is  as  follows :  The  ground  is  graded  and  regulated  with 
a  gutter  18  inches  deep  on  each  side;  the  soil  is  then  thoroughly 
rolled  with  a  15-ton  roller,  and  the  stone  spread  on  the  surface  so  pre- 
pared.  Three  varieties  of  soil  are  met  with  in  Bridgeport :  (I)  a  fine 
"  dead  "  sand,  which  sometimes  cannot  be  rolled  on  account  of  its 
pushing  before  the  roller,  without  covering  it  with  coarse  broken 
stone — this  expedient,  acting  as  a  pavement,  prevents  movement; 
(2)   loam,   and  (3)   a  hard-pan   with   mica  disseminated   through 
it.     Underdraining    has   in    no    case   been    resorted   to,   the   18- 
inch  gutters  being  depended  on  for  drainage.     After  the  broken 
trap-rock  is  rolled  to  a  bearing,  screenings  are  added  as  a  binder 
and  the  road  metal  is  well  and  thoroughly  filled  with  them,  the 
whole  being  rolled  until  the  water  flushes  on  the  surface.     A  strong 
silicious  sand  is  sometimes  used,  in  part,  in  place  of  screenings,  and 
when,  in  dry  weather,  the  road  commences  to  break  up  or  "  ravel," 
out  of  easy  access  by  watering-carts,  sand  is  spread  over  the  spot, 
which  quickly  consolidates  the  road.     No  loam  or  clay  is  used  as  a 
binder  or  'filler  in  the  construction  of  the  roads,  nor  in  their  repair, 
except  when  the  surface  over  a  ditch  is  to  be  replaced  and  it  is  too 
small  a  patch  to  justify  bringing  the  roller;  then  the  broken  trap 
is  laid  down  after  being  mixed  with  the  proper  quantity  of  screen- 


BROKEN-STONE   PAVEMENTS.  293 

ings,  and  the  whole  covered  with  loam.  The  traffic  consolidates  it 
in  a  short  time. 

It  should  be  noticed,  in  connection  with  the  low  cost  of  those 
roads  stated  in  Table  XLII, — about  28  cents  per  square  yard, — that 
Bridgeport,  in  addition  to  the  possession  of  particularly  good  trap- 
rock,  is  exceptionally  favored  in  the  location  of  its  quarry — almost 
exactly  two  miles  from  the  dfentre  of  the  city;  so  that  the  cost  of 
the  stone  is  82  cents  per  gross  ton  of  21  or  22  cubic  feet,  delivered 
to  the  wagons  ;  and  the  cost  of  hauling  varies,  depending  on  the 
distance,  from  50  to  75  cents  per  ton,  or  between  $1.32  and  $1.57 
per  gross  ton  delivered  on  the  road.  The  trap-rock  is  broken  to  2- 
inch  size  by  three  7  X  10-inch  Marsden  crushers,  placed  side  by  side 
on  a  platform,  to  which  cars  are  drawn  from  the  quarry  by  a  wire 
rope,  wound  by  the  same  engine  which  runs  the  crushers.  The  in- 
terest on  the  cost  of  the  roller — an  Aveling  &  Porter,  now  twenty 
years  old — is  not  reckoned  in  the  above-mentioned  cost. 

That  the  cost  of  the  Bridgeport  roads  has  not  been  underesti- 
mated is  apparently  made  certain  by  the  contract  price  of  such 
work  in  the  neighboring  town  of  Fairfield,  where,  with  a  longer 
haul,  a  4-inch  road  20  feet  wide  was  built  for  85  cents  per  lineal 
foot  or  38.3  cents  per  square  yard.  This  sum  included  regulating, 
some  grading,  and  the  use  of  a  roller,  as  well  as  the  contractor's 
profit. 

422.  Extracts  from  Specifications  for  forming  Telford  Roads  in 
St.  Louis,  Mo. 

Drainage. — All  drains  considered  necessary  by  the  Street  Com- 
missioner to  carry  off  the  water  shall,  when  required,  be  made  by 
the  contractor  for  the  work,  and  shall  be  paid  for  at  a  price  agreed 
upon  by  the  Street  Commissioner. 

Sub-foundation. — After  the  curbstones  are  set,  the  second  grad- 
ing and  shaping  of  the  roadway  shall  be  done.  All  surplus  earth 
and  other  material  shall  be  removed  and  the  sub-foundation  formed 
to  a  depth  of  eighteen  (18)  inches  below  the  intended  surface  of  the 
street,  the  cross-section  thereof  to  conform  in  every  respect  to  the 
cross-section  of  the  pavement  when  finished.  The  roadbed  shall 
then  be  rolled  with  a  roller  weighing  not  less  than  five  (5)  tons, 
when  required  by  the  Street  Commissioner.  All  depressions  which 
may  appear  shall  be  carefully  refilled  before  any  stone  is  put  on. 


294  HIGHWAY   CONSTRUCTION. 

Lower  Course  of  Telford. — When  the  street  shall  be  thus  graded 
and  formed,  a  bottom  course  or  layer  of  limestone  of  approved 
quality  shall  be  laid  by  hand  in  regular  straight  courses  at  right 
angles  with  the  line  of  the  streets,  so-  as  to  break  joints;  the  bot- 
tom surfaces  of  the  stones  shall  form  as  close  joints  as  possible. 
The  stones  to  be  used  shall  not  be  less  than  three  (3)  inches  nor 
more  than  eight  (8)  inches  thick,  and  from  five  (5)  to  ten  (10) 
inches  long  on  their  bottom  surfaces,  and  must  be  thoroughly  set- 
tled to  place  with  hammers.  The  interstices  shall  then  be  filled 
with  stone  chips  firmly  wedged  by  hand  with  hammers,  and  all 
projecting  points  shall  be  broken  off.  The  tops  of  the  stones  when 
levelled  off  shall  have  a  surface  not  greater  than  one  third  of  the 
base.  The  foundation  or  bottom  course  when  finished  shall  have 
a  regular  and  uniform  depth  of  not  less  than  seven  (7)  inches. 
The  bottom  course  along  the  curb  and  under  the  gutter  for  a  width 
of  four  (4)  feet,  and  under  the  cross-walk  for  a  width  of  eight  (8) 
feet,  shall  be  thoroughly  consolidated  by  rolling  or  ramming,  and 
the  surface  be  made  even  by  filling  the  spaces  between  the  stones 
with  sand  in  such  manner  as  the  Street  Commissioner  may  direct. 

Guttering. — After  the  Telford  foundation  has  been  prepared 
the  gutter  shall  be  put  down  upon  a  bed  of  clean  coarse  sand  at 
least  two  (2)  inches  deep.  The  paving-blocks  shall  be  from  six  (6) 
to  seven  (7)  inches  deep,  four  (4)  to  six  (6)  inches  thick,  and  eight 
(8)  to  twelve  (12)  inches  long.  The  faces  shall  be  straight,  free 
from  bunches,  depressions,  and  inequalities  exceeding  one  half  (|) 
inch.  The  faces  shall  meet  at  right  angles,  and  the  corresponding 
dimensions  of  opposite  faces  shall  not  vary  more  than  one-half  (J) 
inch.  They  must  be  set  vertically  on  edge,  in  close  contact  with 
each  other,  in  straight  rows  at  right  angles  with  the  curb,  the 
blocks  in  different  rows  breaking  joint  by  a  space  not  less  than 
four  (4)  inches.  The  joints  between  the  blocks  shall  be  filled  with 
clean,  sharp  sand. 

Cross-gutters. — The  cross-gutters  shall  be  of  such  width  and 
shape  as  may  be  directed.  The  stone  used  therefor  shall  be  from 
three  (3)  to  six  (6)  inches  thick,  nine  (9)  inches  deep,  and  from 
six  (6)  to  twelve  (12)  inches  long.  The  bottom  course  of  stone 
shall  be  eight  (8)  inches  thick,  nine  (9)  inches  deep,  and  not  less 
than  twelve  (12)  inches  long. 


BROKEN-STONE   PAVEMENTS.  295 

Quality  and  Finish  of  Stone  Work. — All  stones  used  for 
gutters,  cross-gutters,  and  cross-walks  shall  be  limestone  of  the  best 
quality,  from  ledges  known  to  withstand  the  effects  of  frost,  and 
free  from  seams  and  all  other  defects.  All  paving-stone  shall  be 
dressed  so  as  to  make  close  joints  at  least  four  (4)  inches  deep,  and 
have  a  square  bottom  not  less  than  three  quarters  (J)  of  the  super- 
ficial surface  of  the  top  of  the  same  stone.  All  materials  shall  be 
fully  dressed  before  they  are  brought  onto  the  street  to  be  im- 
proved. The  whole  paving  must  be  made  tight,  compact  and 
smooth,  and  be  fully  fed  with  sand,  and  must  be  laid  true  and  uni- 
form, with  broken  joints,  and  have  a  full  bond  of  at  least  foi\r  (4) 
inches.  After  the  paving  is  laid  it  must  be  sanded  on  top,  th&  sand 
swept  into  the  joints  with  a  broom,  and  be  settled  down  evenly  and 
firmly  with  a- rammer  of  not  less  than  forty  (40)  pounds  weight. 

Macadam  or  Second  Course. — When  the  Telford  foundation  has 
thus  been  formed,  there  shall  be  placed  thereon  a  layer  of  clean, 
hard  limestone  macadam,  free  from  clay,  earth,  rubbish,  or  other 
foreign  matter,  so  broken  that  the  largest  pieces  shall  pass  through 
a  two  and  one  half  (2J)  inch  ring  in  all  their  dimensions,  and  shall 
be  fully  broken  before  it  is  brought  on  the  line  of  work.  This 
course  shall  have  such  a  depth  and  form  of  cross-section  as  may  be 
directed  by  the  Street  Commissioner,  and  shall  be  thoroughly  con- 
solidated by  rolling  with  a  roller  weighing  not  less  than  fiv3  (5)  tons. 

Sand. — The  macadam  course  having  been  finished,  the  spaces 
between  the  stones  shall  be  well  filled  with  clean,  coarse  sand,  or 
so  much  sand  as  may  be  directed  by  the  Street  Commissioner,  which 
shall  be  washed  in  with  water  from  a  hose  having  a  rose  attached 
to  the  nozzle,  and  then  the  whole  shall  be  rerolled  to  the  satisfac- 
tion of  the  Street  Commissioner.  A  sprinkling-cart  shall  not  be 
used  unless  it  is  impossible  to  make  a  connection  with  a  fire-plug, 
and  then  only  with  the  consent  of  the  Street  Commissioner.  A 
water  license  and  a  permit  from  the  Water  Commissioner  must 
first  be  obtained  before  a  fire-plug  can  be  opened. 

Gravel. — The  macadam  course  with  binding  material  having 
been  finished,  there  shall  be  placed  thereon  a  layer  of  good  clean 
gravel,  free  from  clay,  animal,  or  vegetable  matter,  and  containing 
not  more  than  fifteen  (15)  per  cent  of  loam  or  sand,  nor  shall  the 
largest  pebbles  exceed  one  inch  in  diameter;  to  be  well  wetted  down 
or  slushed  with  water  and  thoroughly  rolled  to  a  perfect  surface, 


296 


HIGHWAY   CONSTRUCTION. 


TYPE-SECTIONS  OF  BROKEN-STONE  PAVEMENTS. 


FIG,  25,     COUNTRY  ROAD,  SIDE-DITCH    FILLED  WITH 

COBBLE. 


^ 

>  rjp- 

FIG.  26.      COUNTRY  ROAD,  WITH    EARTH    BERM    AND 

TILE-DRAIN. 


FIG.  27.     CITY   STRE 


FIG,  28.    CITY  STREET,  WITH  STONE-BLOCK  GUTTER. 


BROKEN-STONE    PAVEMENTS.  297 

having  such  form  of  cross-section  and  depth  as  may  be  directed  by 
the  Street  Commissioner. 

423.  Heads  of  Specifications  for  Broken-stone  Pavements. 

(1)  Preparation  of  roadbed. 

(2)  Foundation  (sand,  gravel,  etc.). 

(3)  Quality  of  the  stone. 

(4)  Size  of  the  stone. 

(5)  Cleanness  of  the  stone.     (The  stone  must  at  all  times  be 
clean  and  free  from  clay  or  other  dirt.) 

(6)  Spreading  the  stone. 

(7)  Thickness  of  layers. 

(8)  Eolling :  weight  of  roller  and  amount  of  rolling. 

(9)  Watering. 

(10)  Binding,  quality  and  quantity  of. 

(11)  Interpretation  of  specifications. 

(12)  Omissions  in  specifications. 

(13)  Engineer  defined. 

(14)  Contractor  defined. 

(15)  Notice  to  contractors,  how  served. 

(16)  Preservation  of  engineer's  marks,  etc. 

(17)  Dismissal  of  incompetent  persons. 

(18)  Quality  of  materials. 

(19)  Samples. 

(20)  Inspectors. 

(21)  Defective  work,  responsibility  for. 

(22)  Measurements. 

(23)  Partial  payments. 

(24)  Commencement  of  work. 

(25)  Time  of  completion. 

(26)  Forfeiture  of  contract. 

(27)  Damages  for  non-completion. 

(28)  Evidence  of  the  payment  of  claims. 

(29)  Protection  of  persons  and  property. 

(30)  Indemnity  bond. 

(31)  Bond  for  faithful  performance  of  work. 

(32)  Power  to  suspend  work. 

(33)  Right  to  construct  sewers,  etc. 

(34)  Loss  and  damage. 

(35)  Old  materials,  disposal  of. 


298  HIGHWAY   CONSTRUCTION. 

(36)  Cleaning  up. 

(37)  Personal  attention  of  contractor. 

(38)  Payment  of  workmen. 

(39)  Prices. 

(40)  Security  retained  for  repairs. 

(41)  Payment,  when  made.     Final  acceptance. 


CHAPTER  VIII. 
MISCELLANEOUS  PAVEMENTS.   " 

424.  Gravel  Roads.— Gravel,  though  not  as  durable  as  broken 
stone,  has  proved  very  serviceable  as  a  road  covering. 

In  selecting  gravel  for  this  purpose,  the  chief  quality  to  be 
sought  for  is  the  property  of  binding.  The  binding  properties  are 
two :  the  presence  of  ferruginous  clay,  which  causes  the  gravel  to 
set  or  become  hard  as  soon  as  it  is  exposed  to  the  action  of  the 
atmosphere ;  and  the  angular  shapes  and  sizes  of  the  stones. 

425.  Gravel  from  the  sea-beach  and  shores  of  rivers,  and  that 
in  which  the  stones  are  round  or  oval,  with  regular  smooth  sur- 
faces, never  forms  a  good  binding  material,  even  if  mixed  with 
ferruginous  clay.     The  reason  is  that  the  stones  which  are  on  the 
surface  have  no  mechanical  hold  on  those  which  are  beneath  or  be- 
side them,  but  being  merely  cemented  by  means  of  the  clay  they 
are  easily  loosened  and  thrown  out  of  place  by  the  action  of  the 
traffic  or  frost,  and  even  by  the  alternate  actions  of  drought  and 
moisture. 

426.  When  no  gravel  but  that  found  in  rivers  or  on  the  sea-shore 
can  be  obtained,  one-half  of  the  stones  should  be  broken  and  mixed 
with  the  other  half;  to  the  stone  so  mixed  a  small  quantity  of  clay 
or  loam,  about  one-eighth  of  the  bulk  of  the  gravel,  must  be  added : 
an  excess  is  injurious.     Sand  is  unsuitable :  it  prevents  packing  in 
proportion  to  the  amount  added. 

427.  Preparing:   the    Gravel. — Pit-gravel    usually  contains  too 
much  earth,  and  should  be  screened  before  being  used.    Two  sieves 
should  be  provided, — one  with  meshes  of  one  and  one-half  inches, 
so  that  all  pebbles  above  that  size  may  be  rejected,  the  other  with 
meshes  of  three  quarters  of  an  inch,  and  the  material  which  passes 
through  it  should  be  thrown  away.     The  expense  of  screening  will 
be  more  than  repaid  by  the  superior  condition  of  the  road  formed 

299 


300  HIGHWAY    CONSTRUCTION". 

by  the  cleaned  material,  and  the  diminution  of  labor  in  keeping  it 
in  order.  The  pebbles  larger  than  one  and  a  half  inches  may  ba 
broken  to  that  size  and  mixed  with  the  cleaned  material. 

428.  Laying  the  Gravel. — On  the   roadbed   properly  prepared 
a  layer  of  the  prepared  gravel  four  inches  thick  is  uniformly  spread 
over  the  whole  width,  then  compacted  with  a  roller  weighing  not 
less  than  two  tons,  and  having  a  length  of  not  less  than  thirty 
inches.     The  rolling  must  be  continued  until  the  pebbles  ceases  to 
rise  or  creep  in  front  of  the  roller.     The  surface  must  be  moistened 
by  sprinkling  in  advance  of  the  roller,  but  too  much  water  must 
not  be  used.     Successive  layers  follow,  each  being  treated  in  the- 
above-described  manner  until  the  requisite  depth  and  form    has 
been  attained. 

429.  The  gravel  in  the  bottom  layer  must  be  no  larger  than 
that  in  the  top  layer;  it  must  be  uniformly  mixed,  large  and   small 
together,  for  if  not  so  the  vibration  of  the  traffic  and  the  action  of 
frost  will  cause  the  larger  pebbles  to  rise  to  the  surface  and  the 
smaller  ones  to  descend,  like  the  materials  in  a  shaken  sieve,  and 
the  road  will  never  be  smooth  or  firm. 

The  pebbles  in  a  gravel  road  are  simply  imbedded  in  a  paste 
and  can  be  easily  displaced.  It  is  for  this  reason,  among  others,  that 
such  roads  are  subject  to  internal  destruction. 

430.  The  binding  power  of  clay  depends  in  a  large   measure 
upon  the  state  of  the  weather.     During  rainy  periods  a  gravel  road 
becomes  soft  and  muddy,  while  in  very  dry  weather  the  clay  will 
contract  and  crack,  thus  releasing  the  pebbles,  and  giving  a  loose 
surface.     The  most  favorable  conditions  are  obtained  in  moderately 
damp  or  dry  weather,   during  which  a  gravel  road  offers  several 
advantages   for  light  traffic,  the  character  of  the  drainage,  etc., 
largely  determining  durability,  cost,  maintenance,  etc. 

431.  Repair. — Gravel  roads  constructed  as  above  described  will 
need  but  little  repairs  for  some  years,  but  daily  attention  is  required 
to  make  these.     A  garden  rake  should  be  kept  at  hand  to  draw  any 
loose  gravel  into  the  wheel-tracks,  and  for  filling  any  depressions 
that  may  occur. 

In  making  repairs,  it  is  best  to  apply  a  small  quantity  of  gravel 
at  a  time,  unless  it  is  a  spot  which  has  actually  cut  through.  Two 
inches  of  gravel  at  once  is  more  profitable  than  a  larger  amount. 
Where  thick  coating  is  applied  at  once  it  does  not  all  pack,  and  if, 


MISCELLANEOUS   PAVEMENTS. 


301 


after  the  surface  is  solid,  a  cut  be  made,  loose  gravel  will  be  found; 
this  holds  water  and  makes  the  road  heave  and  become  spouty  under 
the  action  of  frost.  It  will  cost  no  more  to  apply  six  inches  of 
gravel  at  three  different  times  than  to  do  it  all  at  once. 

At  every  one-eighth  of  a  mile  a  few  cubic  yards  of  gravel  should 
be  stored,  to  be  used  in  filling  depressions  and  ruts  as  fast  as  they 
appear,  and  there  should  be  at  least  one  laborer  to  every  five  miles 
of  road. 

432.  Cost  of  Construction  in  Illinois.— The  cost  has  been  about 
1900  per  mile  for  a  roadway  12  feet  wide,  12  inches  deep  at  the 
centre  and  9  inches  at  the  sides. 

Table  XLIII  shows  the  extent  and  cost  of  gravel  pavements  in 
some  of  the  principal  cities  in  the  United  States. 

TABLE  XLIII. 

EXTENT  AND  COST  OP  GRAVEL  PAVEMENTS  IN  SOME  OF  THE  PRINCIPAL 
CITIES  OF  THE  UNITED  STATES. 


Cities. 

Extent. 
Miles. 

Cost  of  Construction 
per  square  yard. 

160.00 

$0.75 

67.91 

liicbniond   Va        .           .         .... 

46.44 

$0  15  to  $0.20 

Washington    D   C  

33.50 

32.37 

Burliu  °"ton   Vt       

11.92 

$0.25 

433.  Weight    of   Gravel.-- -A  cubic  yard  of  pit  gravel  weighs 
about   3300  pounds.     When  the  distance  is  not  greater  than  1£ 
miles,  a  team  will  haul  about  7  cubic  yards  a  day;  even  with  hauls 
of  six  miles  the  work  can  be  done  at  reasonable  cost. 

434.  Bituminous  Macadam. — In  some  towns  in  England  bitu- 
minous or  asphalt  macadamized  roadways  are .  made.    This  consists 
in  mixing  ordinary  coal-tar  with  the  road  metal  ordinarily  employed 
for  macadamized  roads;  only  it  must  be  borne  in  mind  that  the 
metal   employed   must   be   limestone  or  some  other  soft  material, 
otherwise  it  will  not  wear  down  evenly  with  the  tar,  and  thus  a 
lumpy  surface  will  be  produced  in  course  of  time. 

The  method  of  mixing  is  by  heating  the  stone,  which  has  of 
course  been  previously  broken  to  the  required  size,  and  then  thor- 


302  HIGHWAY    CONSTKUCTION. 

oughly  mixing  and  incorporating  it  with  the  tar.  This  is  carried 
to  the  roadway,  is  spread  in  the  ordinary  manner,  and  well  rolled 
to  the  proper  contour,  a  surface  being  afterwards  given  to  it  by  a 
coating  of  about  2  inches  thick,  composed  of  a  similar  mixture,  the 
stones  of  which  are  of  much  smaller  size. 

Another  method  is  to  place  about  6  inches  of  the  broken  stone 
upon  the  necessary  foundation.  Upon  this  a  boiling  mixture,  com- 
posed of  about  50  gallons  of  creosote  oil  and  1  ton  of  pitch,  is 
poured  until  every  interstice  is  filled  with  the  mixture.  Whilst 
this  is  still  warm,  a  thin  layer  of  small  broken  stone  is  spread  upon 
the  surface  and  well  rolled;  more  small  stones  or  chippings  are 
added,  and  the  whole  is  rolled  until  the  surface  of  the  roadway  has 
attained  its  proper  contour  and  presents  a  perfectly  smooth  and 
clean  appearance,  little  inferior  to  that  of  real  asphalt. 

Dry  weather  is  essential  whilst  this  class  of  roadway  is  in  course 
of  construction,  and  careful  watching  is  required,  as  when  the  skin 
breaks  the  whole  roadway  soon  disintegrates.  This  class  of  pave- 
ment has,  however,  many  advantages  over  ordinary  macadamized 
roadways  when  finished,  not  the  least  of  them  being  impervious- 
ness  to  moisture,  and  the  ease  with  which  it  may  be  cleaned. 

435.  In  repairing  some  of  the  macadam  roads  and  pavements  in 
Paris,  fragments  of  old  asphalt  were  mixed  with  the  broken  stone. 
The  results,  as  regards  wearing  qualities,  show  little  improvement 
over  the  unmixed  stone,  but  such  a  pavement  keeps  remarkably 
clean  during  dry  weather  and  does  not  become  as  muddy  as  the  true 
macadam  during  rainy  seasons. 

In  the  middle  of  summer  an  unpleasant  odor  is  given  out,  and 
the  surface  has  a  dirty  black  color. 

436.  Concrete  Macadam,  introduced  by  Mr.  J.  Mitchell,  London 
Eng.,  is  composed  of  broken  stone,  sand,  and  Portland  cement  so 
proportioned  that  the  spaces,  otherwise  vacant,  and  ultimately  filled 
with  muddy  cementing  matter  of  worn  macadam,  are  filled  with  an 
admixture  of   Portland  cement   or  other   hydraulic  cement-grout. 
The  concrete  thus  formed  rapidly  becomes  a  uniform  and  impervious 
mass  which  is  wholly  unaffected  by  heat  or  moisture.     It  is  mixed 
in  these  proportions: 

Broken  stones 4  measures 

Clean,  sharp  sand 1J  to  1£        " 

Portland  cement 1          " 


MISCELLANEOUS   PAVEMENTS.  305 

So  for  a  cubic  yard,  or  27  cubic  feet,  of  broken  metal  6f  cubic 
feet,  or  1£  barrels  (of  4£  cubic  feet),  of  Portland  cement  are  re- 
quired. The  broken  stone  should  be  of  the  hardest  quality,  of 
uniform  size,  thoroughly  screened;  and  it  should  be  thoroughly 
wetted  before  being  incorporated  with  the  cement. 

Cement  of  the  best  quality  must  be  employed,  and  the  sand 
should  be  sharp,  clean,  and  gritty.  The  surface  of  the  ground  is. 
brought  to  form,  and  rolled  several  times.  The  concrete  is  then 
laid  on  the  surface  in  a  layer  3  or  4  inches,  and  is  left  for  three-, 
days  to  harden.  The  second  layer  of  3  or  4  inches  is  next  laid  on. 
the  first,  and  immediately  rolled  to  form  with  a  heavy  iron  roller, 
as  heavy  as  two  or  three  men  can  draw.  The  cement  should  be  left 
for  three  weeks,  to  allow  it  to  become  quite  hard  before  the  road  is 
opened  for  traffic,  although  a  week  has  been  found  to  be  a  sufficient 
interval. 

Mr.  Mitchell  states  that  a  concrete  road,  7  inches  deep  at  th& 
middle  and  5  inches  at  the  sides,  is  sufficient  for  ordinary  traffic. 
For  heavy  traffic  a  depth  of  8  inches  is  recommended. 

The  first  piece  of  concrete  road  was  laid  in  1865  in  Inverness,, 
and  consisted  of  45  lineal  yards  of  the  approach  to  the  freight  sta- 
tion of  the  railway.  In  1870,  after  the  road  had  been  under  traffic-, 
for  4^  years,  it  was  reported  that  the  wear  of  the  surface  was  scarcely 
appreciable,  whilst  the  adjoining  macadamized  road  had  been  coated 
frequently  every  year. 

Another  specimen,  50  yards  long  and  15  yards  wide,  was  laid  in 
1866,  on  George  IV.  Bridge,  Edinburgh,  where  the  traffic  is  heavy 
and  continuous.  At  the  end  of  three  years  and  a  half  under  traffic: 
the  surface  was  perfectly  sound  and  immovable. 

The  amount  of  vertical  wear  during  the  periods  above  named 
appears  not  to  have  exceeded  i  inch.  But  Mr.  J.  H.  Cunningham, 
writing  in  January,  1875,  stated  that  it  was  then  much  worn  at  the 
surface,  in  consequence,  he  thought,  of  its  great  hardness  and 
rigidity. 

437.  Stone  Trackways  (Figs.  29  to  32). — Trackways  formed  of 
stone  slabs  were  first  employed  by  the  Egyptians  for  moving  great 
weights.  In  modern  times  they  reappeared  in  northern  Italy,  where 
they  are  in  general  use  not  only  in  the  streets  of  the  principal  cities, 
but  also  in  the  smaller  towns. 

Telford  employed  a  stone  trackway  on  the  Holyhead  Koad  to> 


304 


HIGHWAY   CONSTRUCTION. 


FIG.  29-— SECTION  OF  STONE  TRACKWAY. 


FlG.  30.-PLAN  OF  TRACKWAY. 


FlG.  31.— PLAN  OF  CROSSING. 


MISCELLANEOUS   PAVEMENTS 


305 


FIG,  32,— JUNCTION  OF  CURVES  WITH  STRAIGHT  LINE. 


306  HIGHWAY   CONSTRUCTION. 

avoid  excessive  work  of  construction.  There  were  two  hills  each  a 
mile  in  length,  with  an  inclination  of  5  :  100.  To  reduce  this  to  a 
4£  per  cent  grade  would  have  cost  $100,000,  but  nearly  the  same 
advantage  in  diminishing  the  amount  of  tractive  force  required  was 
obtained  by  making  stone  trackways  at  a  total  expense  of  one  half 
the  former  amount  and  retaining  the  5  per  cent  grade  with  moderate 
cutting  and  embankment.  To  draw  one  ton  over  the  original 
hills  required  a  tractive  force  of  294  pounds;  to  draw  the  same  load 
over  the  trackways  laid  on  the  same  inclinations  required  only  132 
pounds. 

Trackways  of  both  stone  and  iron  have  been  used  in  Londo^ 
Liverpool,  Manchester,  Glasgow,  and  other  cities. 

438.  The  Italian  trackways  consist  of  two  parallel  lines  of  granite 
blocks,  usually  14  inches  wide,  8  inches  deep,  and  5  feet  in  length,, 
bedded  in  a  layer  of  sand.    The  lines  are  28  inches  apart,  and  the  in- 
terspace, or.  footway  for  horses,  as  well  as  the  other  portions  of  the 
roadway,  is  paved  with  cobbles  obtained  from  the  Po,  or  from  other 
rivers.     These  stones  should  be  egg-shaped,  with  a  maximum  diame- 
ter of  from  3J  to  4|  inches  and  a  depth  of  from  4£  to  5J  inches. 
The  roadway  is  usually  formed  with  a  slight  inclination  downwards, 
towards  the  centre.     By  this  arrangement  the  space  between  the 
trams  serves  as  a  channel  to  receive  the  surface-water,  and  is  provided 
with  stone  gratings,  placed  at  suitable  intervals,  by  which  the  water 
escapes  into  the  sewers.     The  surfaces  of  the  trams  are  slightly  in- 
clined towards  each  other,  the  inner  edges  being  f  inch  lower  than, 
the  outer  edges;  whilst  the  interspace  is  concave,  having  a  versed  sine 
or  depression  of  1 J  inches.    The  foundation  of  the  roadway  consists 
of  a  layer  of  screened  gravel,  about  6  inches  deep,  watered  so  as  to 
form  a  compact  mass.     Two  inches  of  sand  is  laid  on  the  gravel,  as 
a  bed  for  the  paving-stones.     The  upper  surfaces  of  the  trams  are 
dressed  flat  and  the  ends  square,  to  form  close  joints.     The  stone 
gratings  for  the  gulleys  are  32  inches  long,  formed  with  three  slots 
12  inches  long  and  1-J-  inches  wide.    After  the  trams  are  placed,  the 
other  portions  of  the  pavement  are  completed.     After  the  surface 
has  been  well  rammed  with  a  wooden  rammer,  it  is  watered  and 
covered  with  a  bedding  of  sand  f  inch  deep,  so  as  to  fill  the  joints 
by  degrees.      On  steep  gradients  the  surfaces  of  the  trams  are 
grooved  diagonally. 

439.  Trackways  are  expensive  to  construct  (cost  about  $14,000 


MISCELLANEOUS    PAVEMENTS.  307 

per  mile  for  two  lines  of  track  and  intermediate  paving  in  the 
neighborhood  of  New  York),  but  cost  little  for  repairs  and  mainte- 
nance. Their  advantages  are  many:  they  combine  the  opposite 
qualities  required  for  easy  haulage,  viz.,  a  smooth  surface  for  the 
wheels,  on  which  the  friction  is  reduced  to  the  least  possible  amount, 
and  a  rough  footway,  affording  a  firm  foothold  for  horses,  thus 
enabling  them  to  exert  their  utmost  tractive  power.  For  this  reason 
they  ought  to  receive  more  attention  than  is  now  accorded  them. 
The  friction  of  their  surface  is  only  about  T^-¥  of  the  load,  or  about 
one  half  that  of  the  best  block  pavement.  It  is  stated  that  on  such 
trackways  in  London  a  horse  weighing  about  700  pounds  could 
draw  on  a  level  15  tons,  and  a  horse  weighing  about  1600  pounds 
could  draw  30J-  tons. 

440.  In  Glasgow,  Scotland,  there  was  a  trackway  down  for  forty 
years.     It  consisted  of  cast-iron  plates  2  inches  thick,  8  inches 
wide,  and  cast  in  lengths  of  3  feet.    It  was  laid  in  Buchanan  Street 
on  a  5  per  cent  grade. 

441.  The   trackways   for  the  wheels   may  be  of  granite,   or 
compact  sandstone  slabs  12  to  24   inches  wide,  6   inches  thick, 
and  in  lengths  of  2  to  6  feet.     The  footway  for  the  horses  to  be  in 
all  cases  paved  with  cobblestones  the  other  portions  of  the  road- 
way may  be  paved  with  cobblestones,  granite,  or  other  pavement. 

The  foundation  for  the  trackways  should  be  constructed  as  shown 
in  Fig.  29,  with  all  the  joints  filled  with  asphaltic  paving-cement. 

The  roadway  may  be  formed  in  the  usual  manner  with  the 
trackways  level  (transversely),  the  surface  falling  from  their  outer 
edge  to  the  gutters;  but  at  frequent  intervals  in  the  horse-path 
catch-basins  with*  iron  or  stone  covers  should  be  placed,  connecting 
with  the  sewer.  At  track-crossings  or  junctions  the  surface  of  the 
slabs  should  be  grooved,  so  as  to  afford  good  foothold  for  the  horses 
passing  over  them. 

442.  "  Jasperite."— Jasperite,  under  what  is  known  as  "  Drake's 
Patent,"  consists  of  quartzite  crushed  to  sizes  of  J,  J,  and  £  of  an 
inch,  and  known  as  Nos.  3,  4,  and  5,  respectively.     The  foundation 
is  composed  of  irregularly  broken  stone  set  to  form  a  rough  pave- 
ment similar  to  that  used  for  a  Telford  road.     On  this  is  spread  a 
layer  of  concrete  1^  inches  thick,  composed  as  follows :  1  part  of 
Portland  cement,  1  part  of  sand,  and  3  parts  of  quartzite  of  the 
sizes  Nos.  3  and  4.     This  is  well  mixed,  spread,  and  rammed  into 


308  HIGHWAY    CONSTRUCTION. 

place  in  such  a  manner  as  to  form  blocks  one  yard  square.  These 
blocks  are  separated  by  tarred  paper.  On  the  bed  so  formed  is 
spread  a  layer  one-half  inch  in  thickness,  prepared  in  the  same  way, 
but  substituting  quartzite  of  the  size  known  as  No.  5.  This  pave- 
ment is  in  use  in  Sioux  Falls,  S.  D.,  and  Wichita,  Kan.  The  cost 
per  square  yard  is  about  $2.50,  with  a  five-year  guarantee. 

443.  Artificial  Granite  Blocks  are  formed  from  the  chippings  of 
granite  quarries.     It  is  mixed  at  the  place  where  it  is  to  be  used 
with  Portland  cement  in  sufficient  quantity  to  make  a  thorough 
bond  between  the  pieces,  and  put  down  in  blocks  or  squares  so  as 
to  form  separate  stones  as  it  were.     Its  surface  is  kept  compara: 
tively  rough  by  the  cement  wearing  below  the  points  of  the  granite. 
Its  advantage  is,  presumably,  cheapness. 

444.  Plank  Roads. — In  localities  where  timber  is  abundant  and 
other  materials  are  unobtainable,  planks  may  be  employed  to  form 
pavements.     When  new  and  well  laid  they  form  a  comfortable  car- 
riageway both  for  haulage  and  pleasure,  but  make  when  worn  and 
displaced  a  very  disagreeable  road. 

445.  The  method  most  generally  adopted  in  constructing  plank 
roads  consists  in  laying  a  flooring  or  track  8  feet  wide,  composed  of 
boards  from  9  to  12  inches  in  width  and  3  inches  in  thickness, 
which  rest  upon  two  parallel  rows  of  stringers  or  sills  laid  length- 
wise in  the  road  and  having  their  centre  lines  about  4  feet  apart  or 
2  feet  from  the  axis  of  the  road.     Sills  of  various-sized  scantling 
have  been  used,  but  experience  seems  in  favor  of  scantling  about 
12  inches  in  width,  4  inches  in  thickness,  and  in  lengths  of  not 
less  than  15  to  20  feet.     Sills  of  these  dimensions  laid  flatwise  and 
firmly  embedded  present  a  firm  and  uniform  bearing  to  the  boards 
and  distribute  the  pressure  they  receive  over  so  great  a  surface  that, 
if  the  soil  upon  which  they  rest  is  compact  and  is  kept  well  drained, 
there  can  be  but  little  settling  and  displacement  of  the  road-surface 
from  the  usual  loads  passing  over  it.     The  better  to  secure  this  uni- 
form distribution  of  the  pressure,  the  sills  of  one  row  are  so  laid  as 
to  break  joints  with  the  other,  and  to  prevent  the  ends  of  the  sills 
from  yielding  the  usual  precaution  is  taken  to  place  short  sills  at 
the  joints,  either  beneath  the  main  sills  or  on  the  same  level  with 
them. 

The  boards  are  laid  perpendicular  to  the  axis  of  the  road,  ex- 
perience having  shown  that  this  position  is  more  favorable  to  their 


MISCELLANEOUS   PAVEMENTS.  309 

wear  and  tear  than  any  other,  and  is  besides  the  most  economical. 
Their  ends  are  not  in  an  unbroken  line,  but  so  arranged  that  the 
ends  of  every  three  or  four  project  alternately,  on  each  side  of  the 
axis  of  the  road,  3  or  4  inches  beyond  those  next  to  them,  for  the 
purpose  of  presenting  a  short  shoulder  to  the  wheels  of  vehicles  to 
facilitate  their  coming  upon  the  plank  surface  when  from  any  cause 
they  may  have  turned  aside.  On  some  roads  the  boards  have  been 
spiked  to  the  sills,  but  this  is  unnecessary,  the  stability  of  the 
boards  being  best  secured  by  well  packing  the  earth  between  and 
around  the  sills,  so  as  to  present  a  uniform  bearing  surface  to  the 
boards,  and  by  adopting  the  usual  precautions  for  keeping  the  sub- 
soil well  drained  and  preventing  any  accumulation  of  rain-water 
on  the  surface.  The  boards  for  plank  roads  should  be  selected  from 
timber  free  from  the  usual  defects,  such  as  knots  and  shakes,  which 
would  render  it  unsuitable  for  ordinary  purposes,  as  durability  is  an 
essential  element  in  the  economy  of  this  class  of  road-construction. 
Boards  of  3  inches  in  thickness  offer  all  the  requisites  of  strength 
and  durability  that  can  be  obtained  from  timber  in  its  ordinary  state, 
in  which  it  is  used  for  plank  roads. 

Besides  the  wooden  track  of  8  feet,  an  earthen  track  of  12  feet 
in  width  is  made,  which  serves  as  a  summer  road  for  light  vehicles 
and  as  a  turnout  for  loaded  ones.  This,  with  the  wooden  track, 
gives  a  clear  road-surface  of  20  feet,  the  least  that  can  be  well 
allowed  for  a  frequented  road.  It  is  recommended  to  lay  the 
wooden  track  on  the  right-hand  side  of  the  approach  of  a  road  to  a 
town  or  village,  for  the  proper  convenience  of  the  rural  traffic,  as 
the  heavy  trade  is  to  the  town.  The  surface  of  this  track  receives 
a  cross-slope  from  the  side  towards  the  axis  of  the  road  outwards  of 
1  in  32.  The  surface  of.  the  summer  road  receives  a  cross-slope  in 
the  opposite  direction  of  1  in  16.  These  slopes  are  given  for  the 
purpose  of  facilitating  a  rapid  surface  for  draining.  The  side 
drains  are  placed  for  this  purpose  parallel  to  the  axis  of  the  road 
and  connected  with  the  surface  in  a  suitable  slope. 

Where  from  the  character  of  the  soil  good  summer  roads  cannot 
be  had,  it  would  be  necessary  to  make  wooden  turnouts  from  space 
to  space,  to  prevent  the  inconvenience  and  delay  of  miry  roads. 
This  can  be  effected  by  laying  at  these  points  a  wooden  track  of 
double  width,  to  enable  vehicles  meeting  to  pass  each  other.  It  is 
recommended  to  lay  these  turnouts  on  four  or  five  sills,  to  spring 


310  HIGHWAY   CONSTRUCTION. 

the  boards  slightly  at  the  centre,  and  spike  their  ends  to  the  ex- 
terior sills. 

In  some  of  the  earlier  plank  roads  a  width  of  16  feet  was  given 
to  the  wooden  track,  the  boards  of  which  were  laid  upon  four  or 
five  rows  of  sills.  But  experience  soon  demonstrated  that  this  was 
not  an  economical  plan,  as  it  was  found  that  vehicles  kept  the 
centre  of  the  wooden  surface,  which  was  soon  worn  into  a  beaten 
track,  whilst  the  remainder  was  only  slightly  impaired.  This  led 
to  the  abandonment  of  the  wide  track  for  the  one  now  usually  em- 
ployed, which  answers  all  the  purposes  of  the  traffic  and  is  much 
more  economical,  both  in  the  first  outlay  and  for  subsequent  re- 
newals and  repairs.  Plank  roads  possess  great  advantages  in  a 
densely-wooded  country,  and  will  be  found  superior  to  every  other 
kind  as  a  temporary  expedient. 

446.  The  cost  per  mile  ranges  from  $1000  to  $4000,  and  the  life 
is  about  eight  years. 

447.  Log  Roads. — When  a  road  passes  over  soft  swampy  ground, 
always  kept  moist  by  springs  which  cannot  be  drained  without  too 
much  expense,  and  which  is  surrounded  by  a  forest,  it  may  be 
cheaply  and  rapidly  made  passable  by  felling  a  sufficient  number 
of  young  trees,  as  straight  and  as  uniform  as  possible,  and  laying 
them  side  by  side  across  the  road  at  right  angles  to  its  length. 
This  arrangement  is  well  known  under  the  term  "corduroy  road." 
Though  its  successive  hills  and  hollows  offer  great  resistance  to 
draught  and  are  very  unpleasant  to  persons  riding  over  it,  it  is 
nevertheless  a  very  valuable  substitute  for  a  swamp,  which  in  its 
natural  state  would  at  times  be  utterly  impassable. 

448.  Charcoal. — In  some  of  the  Western  States,  where  wood  is 
abundant  and  cheap,  roads  covered  with  charcoal  have  been  made 
as  follows :  Logs  from  six  inches  to  two  feet  in  diameter  and  from 
twelve  to  twenty-four  feet  long  are  cut  and  piled  lengthwise  along 
the  road  about  six  feet  high,  being  nine  feet  on  the  bottom  and 
two  on  top,  and  then  covered  with  straw  and  earth,  or  simply  with 
sods,  and  burned  in  the  manner  of  coal-pits.      The  covering  is 
taken  from  the  sides  of  the  road,  and  the  ditches  thus  formed 
afford  good  drainage.     After  the  timber  is  converted  into  charcoal, 
the  earth   is  removed  to  the  side  of  the  ditches,  the  coal  raked 
down  to  a  width  of  fifteen  feet,  leaving  it  two  feet  thick  at  the  cen- 
ter and  one  at  the  sides,  and  the  road  is  completed. 


MISCELLANEOUS   PAVEMENTS.  311 

449.  A  road  thus  made  in  Michigan  cost  $660  per  mile,  and  is 
said  to  be  very  compact  and  free  from  mud  or  dust.     At  a  season 
ivhen  the  mud  on  the  adjoining  earth  road  was  half-axletree  deep, 
on  the  coal  road  there  was  not  the  least  standing,  and  the  impress 
of  the  feet  of  a  horse  passing  rapidly  over  it  was  like  that  made  on 
hard -washed  sand,  as  the  surf  recedes,  on  the  shore  of  the  lake. 
The  water  was  not  drained  from  the  ditches,  and  yet  there  were  no 
ruts  or  inequalities  in  the  surface  of  the  coal  road,  except  what  was 
produced  by  more  compact  packing  on  the  line  of  travel.     It  is 
probable  that  coal  will  fully  compensate  for  the  deficiency  of  lime- 
stone and  gravel  in  many  sections  of  the  West,  and,  where  a  road  is 
to  be  constructed  through  forest  land,  that  coal  may  be  used  at  a 
fourth  the  expense  of  limestone. 

450.  Iron. — Iron  is  eminently  durable,  but  as  a  pavement  it  is 
&  failure.     It  is  so  slippery  even  when  roughened  that  horses  can- 
not gain  a  foothold  on  it.     About  thirty  years  ago  Cortlandt  Street 
in  New  York  was  paved  with  it.    In  order  to  guard  against  slipper- 
iness  the  surface  was  made  rough  and  consisted  of  hexagonal  pro- 
jections about  an  inch  in  size,  separated  by  depressions  of  about 
the  same  size.     It  was  both  rough  and  noisy;   the  horses  caught 
their  calks  in  the  depressions  and  twisted  off  their  shoes,  and  in 
spite  of  its  roughness  the  horses  fell  frequently  and  with  disastrous 
results  in  tearing  their  knees  on  the  sharp  projections.     It  remained 
in  use  but  a  short  time  and  was  replaced  with  stone.     Combinations 
of  wood  and  iron,  concrete  and  iron,  are  frequently  introduced  and 
experimented  with,  but  so  far  none  have  been  a  practical  success. 

45  Oa.  Furnace  Slag. — Slag  and  cinders  from  iron  and  copper 
ivorks  may  be  employed  with  advantage  when  they  are  procurable, 
and  when  no  stone  sufficiently  tough  to  withstand  the  action  of 
heavy  traffic  can  be  obtained.  They  are  both  very  durable,  but 
care  is  required  in  the  selection  of  the  tougher  sorts.  They  have 
no  binding  properties,  and  on  this  account  are  sometimes  used  with 
limestone;  a  rough  surface  will,  however,  always  result  from  the 
unequal  wear  of  two  materials  so  different  in  hardness.  Limestone 
scrapings,  coal  ashes  or  clay,  laid  on  as  a  binding  material,  aid  con- 
solidation very  much,  and  also  prevent  injury  to  horses'  feet  from 
the  sharp  edges  of  the  fresh-laid  slag. 

450b.  Blocks  formed  by  casting  furnace  slag  in  moulds  are  in  use 
in  England  and  other  parts  of  Europe.  Their  quality  varies  with 


312  HIGHWAY    CONSTRUCTION. 

the  amount  of  silica  contained  :  if  this  be  about  35  per  cent,  the- 
resulting  blocks  are  tough ;  but  if  below  30  per  cent,  the  block  is 
brittle  and  easily  broken.  The  process  employed  in  England  for  the 
manufacture  of  these  blocks,  and  which  seems  to  produce  a  tough 
and  durable  article,  is  to  run  the  slag  from  the  furnace  into  a  ladle, 
then  pour  it  from  this  into  iron  moulds  of  the  desired  shape  and  size 
contained  on  an  iron  plate  arranged  to  revolve;  contact  with  the 
moulds  chills  the  outside  of  the  slag  block  immediately,  and  as  the 
plate  makes  a  half  revolution  the  bottom  of  the  mould  is  opened 
by  mechanical  means  and  the  chilled  block  dropped  either  on  a  bed 
of  sand  or  a  conveyor.  From  here,  and  while  the  interior  of  the 
block  is  still  in  a  molten  condition,  it  is  placed  in  an  annealing  oven, 
which,  when  fully  charged,  is  sealed  and  allowed  to  cool,  no  heat 
being  used  other  than  that  furnished  by  the  blocks  themselves.* 

450c.  Chert. — This  material  is  employed  for  street  and  road 
paving  in  some  of  the  Southern  States,  notably  Alabama,  where  it  is. 
found  in  inexhaustible  quantities  overlying  the  red  sandstone,  which 
forms  the  covering  of  the  red  hematite  iron  ore,  and  underlying  the 
sub-carboniferous  limestone.  The  cities  of  Montgomery  and  Bir- 
mingham, Ala.,  and  Macon  and  Savannah,  Ga.,  have  several  miles 
of  streets  paved  with  it.  There  is  also  in  both  States  several  miles 
of  country  roads  covered  with  it. 

Chert  is  a  valuable  substitute  for  broken  stone,  especially  where 
stone  is  scarce  or  of  unsuitable  character;  it  furnishes  an  excellent 
surface  and  wears  well  under  traffic  with  but  little  dust  or  mud. 

The  material  is  usually  laid  upon  a  foundation  of  furnace  slag  or 
other  convenient  material,  but  in  the  absence  of  such  it  is  laid  di- 
rectly upon  the  earth  surface.  The  thickness  employed  varies  from 
3  to  5  inches.  It  is  simply  spread,  sprinkled,  and  rolled.  In  Bir- 
mingham, Ala.,  the  cost  of  the  chert  is  80  cents  per  cubic  yard  on 
the  street,  and  the  cost  of  the  furnace  slag,  including  hauling, 
spreading,  and  rolling,  is  from  30  to  40  cents  per  cubic  yard. 

The  name  "chert"  is  also  applied  to  the  slag  derived  from  the 
blast  furnaces  in  Alabama.  This  material  is  also  employed  for 
street  and  road  paving. 

450d.  Florida  Clay. — -This  name  is  given  to  a  sandstone  rock  de- 

*  Scoria  blocksare  rarely  free  from  internal  cavities.  When  these  are  located 
near  the  upper  surface  the  destruction  of  the  block  is  materially  accelerated. 


MISCELLANEOUS   PAVEMENTS.  313 

posit  found  in  Florida,  the  material  from  which  has  been  extensively 
used  in  several  towns  of  Florida  for  street  and  sidewalk  paving.  Its 
use  has  been  the  means  of  converting  streets  so  sandy  that  travel 
over  them  was  very  slow  and  difficult  into  driveways  over  which 
travel  is  easy  and  pleasant. 

The  composition  of  this  "clay"  is  as  follows : 

Moisture 4.20  per  cent. 

Silica 69.03    "      " 

Aluminum  silicate , . .  18.21    "      " 

Ironoxide 8.53    "      " 

Calcium  carbonate trace. 

The  most  valuable  constituent  of  this  material,  when  used  as  a 
covering  for  roads,  is,  no  doubt,  the  oxide  of  iron,  which  acts  as  a  ce- 
ment, rendering  the  material  capable  of  becoming  compact  and  hard. 

For  use  the  material  is  quarried  and  without  any  preparation  is 
spread  over  the  roadway  to  the  depth  of  several  inches,  then 
sprinkled  with  water  and  compacted  with  a  roller.  It  is  of  a  red- 
dish color,  due  to  the  presence  of  the  oxide  of  iron.  After  being 
travelled  over  for  a  short  time  it  becomes  very  compact  and  nearly 
as  hard  as  it  was  in  its  native  bed. 

450e.  Tar-macadam. — A  paving  composition  called  "tar-mac- 
adam "  has  been  introduced  in  England  ;  it  consists  of  granite, 
coal-tar,  refined  asphaltum,  and  creosote  oil  in  the  proportions  of 
1  ton  of  granite  broken  into  1^-inch  fragments,  12  gallons  of 
coal-tar,  28  pounds  of  asphaltum,  and  2  gallons  of  creosote  oil; 
the  ingredients  are  heated  and  thoroughly  incorporated.  The 
pavement  is  formed  as  follows  :  The  foundation  is  composed  of  a 
layer  of  hard  clinkers  and  broken  stone,  10  inches  in  thickness,  well 
consolidated  by  rolling  with  a  12-ton  steam-roller;  this  is  covered 
with  a  layer  4  inches  thick  of  stone  broken  into  2^-inch  fragments. 
This  is  also  compacted  by  rolling;  upon  this  is  spread  a  3-inch 
layer  of  the  "tar-macadam";  this  is  thoroughly  compacted  by  rolling 
and  then  covered  with  a  1-inch  layer  of  limestone  screenings  mixed 
with  the  same  cementing  materials  that  are  used  in  the  macadam. 
This  last  layer  is  sprinkled  with  clean  dry  limestone  screenings 
and  rolled.  The  work  should  only  be  done  in  dry  weather;  the 
rolling  should  average  10  hours  for  each  100  square  yards,  and  the 
traffic  should  not  be  admitted  until  afc  least  24  hours  after  the  work 
is  completed.  The  cost  is  from  84  cents  to  $1.00  per  square  yard. 


314  HIGHWAY   CONSTRUCTION. 

450f.  Artificial  Stone.  * — Pavements  formed  of  artificial  stone  or 
concretes  composed  of  hydraulic  cement,  crushed  stone,  sand,  and 
gravel,  with  sometimes  the  addition  of  some  indurating  mineral 
substance,  as  baryta,  litharge,  etc.,  have  been  tried;  they  are  usually 
manufactured  under  a  patent,  either  in  place  or  in  the  form  of 
blocks  at  a  factory.  While  artificial  stone  is  eminently  suitable  as 
a  paving  material  for  footwalks,  it  quickly  fails  under  the  action 
of  horses'  hoofs  and  wheels  when  used  as  a  carriageway  pavement. 

450g.  Hydraulic  cement  concrete  is  used  in  several  cities  as  a  pav- 
ing material  foralleys  and  is  found  very  suitable;  the  following  speci- 
fications show  how  these  pavements  are  formed  (see  also  Art.  786) : 

Specifications  for  Hydraulic  Cement  Pavement. — The  material 
shall  be  excavated  from  the  entire  area  proposed  to  be  paved  to  a 
depth  of  eighteen  (18)  inches  below  the  surface  of  the  finished 
pavement;  the  excavation  thus  formed  shall  be  filled  to  a  depth  of 
fourteen  (14)  inches  with  clean  steam  ashes  or  cinders,  and  these 
shall  be  thoroughly  compacted  by  ramming.  Upon  the  foundation 
so  formed  shall  be  laid  a  concrete  composed  of  1  part  of  Portland 
cement  (either  of  Hilton  or  Manheimer  brand)  and  3  parts  of 
clean,  sharp,  coarse  sand,  thoroughly  mixed  dry  and  made  into 
mortar  with  the  least  quantity  of  water,  and  thoroughly  intermixed 
with  broken  stone  or  furnace  slag  in  such  quantity  (about  7  parts) 
that,  when  tamped  or  rammed  solidly  in  place,  free  mortar  will 
rise  to  the  surface  and  exhibit  a  depth  of  three  (3)  inches  of  the 
said  concrete.  Upon  this  concrete  foundation  a  surface  mixture 
shall  be  laid  one  (1)  inch  in  thickness,  composed  of  1.  part  of 
Portland  cement  (Dyckerhoff  or  Star  Stettin' brand)  and  2  parts 
of  crushed  granite,  with  just  sufficient  water  to  make  a  stiff  mor- 
tar; this  surface  coat  shall  be  thoroughly  compacted  by  tamping; 
and  shall  be  dressed  with  a  small  quantity  of  dryer,  composed  of 
one  half  pure  cement  and  one  half  flint  sand,  floated  over  the  entire 
surface  as  a  finish. 

450h.  Clinkers. — The  clinkers  produced  by  burning  street 
sweepings  and  garbage  and  the  debris  produced  in  the  manufacture 
of  gas,  consisting  of  the  clinkers,  old  retorts,  fire-bricks,  ash-pan 
and  coke  refuse,  have  all  been  tried  for  paving  both  footpaths  and 

*  Is  used  to  some  extent  for  the  paving  of  carriageways  in  Bellefontuine, 
O.,  Sioux  Falls,  S.  Duk.,  Grenoble,  France,  and  in  several  cities  in  Germany. 
For  the  paving  of  alleys  it  is  used  in  Philadelphia  and  other  cities. 


MISCELLANEOUS   PAVEMENTS.  315 


carriageways;  in  the  former  they  are  generally  satisfactory,  but  in 
the  latter  they  quickly  fail. 

The  materials  are  prepared  for  use  by  crushing  to  a  size  of 
about  one  inch;  the  crushed  material  is  screened;  the  portion  that 
will  not  pass  through  a  one-quarter  inch  screen  is  used  for  the  top 
finish,  and  the  coarser  portion  for  the  foundation.  The  materials 
so  separated  are  mixed  with  either  Portland  cement  or  coal-tar,  and 
laid  in  place  in  the  usual  manner;  or  they  may  be  formed  into 
blocks  at  a  factory  and  shipped  to  the  place  of  use.  (Mixed  with 
•cement  it  is  used  at  Hersey,  a  suburb  of  London,  and  is  said  to  give 
satisfaction.) 

450i.  Glass. — An  experiment  with  this  material  is  being  made 
in  Lyons,  France;  the  Rue  de  la  Republique  has  been  paved  with 
ceramocrystal,  or  devitrified  glass.  This  new  product  is  obtained 
from  broken  glass  heated  to  a  temperature  of  1250C  F.  and  com- 
pressed in  matrices  by  hydraulic  force.  The  glass  pavement  is 
laid  in  the  form  of  blocks  8  inches  square,  each  block  containing 
sixteen  parts  in  the  form  of  checkers.  These  blocks  are  so  closely 
fitted  together  that  water  cannot  pass  between  them,  and  the 
whole  pavement  looks  like  one  gigantic  checker-board  As  a  pave- 
ment it  is  said  to  have  a  greater  resistance  than  stone,  it  is  a  poor 
conductor  of  cold,  and  ice  will  not  form  on  it  readily;  dirt  does 
not  accumulate  upon  it  so  easily  as  upon  stone,  and  it  will  not 
retain  microbes. 

450j.  Novaculite  (from  the  Latin  novacula,  a  razor)  is  an  un- 
crystallized  quartzite,  very  much  like  flint,  and  occurs  in  large 
quantities  in  southern  Illinois,  Missouri,  and  Arkansas.  It  is  em- 
ployed  for  carriageway  and  sidewalk  paving  (under  a  patent)  and 
appears  to  give  satisfaction.  Its  composition  is  stated  to  be  as 
follows : 

Silica 94.48 

Alumina 1.28 

Iron  oxide 3.12 

Loss  by  ignition 1.18 

100.00 

Prof.  J.  B.  Johnson  says  it  is  the  hardest  of  rocks,  scratches 
glass  like  a  diamond,  and  resists  all  disintegrating  action  of  the 
weather. 


316  HIGHWAY   CONSTRUCTION. 

450k.  Destructor  Concrete. — In  several  English  cities  where  cre- 
matories are  employed  for  the  destruction  of  the  garbage,  etc.,  the- 
clinker  therefrom  is  used  for  making  concrete  slabs.  The  clinker 
is  ground  very  fine,  and  mixed  in  the  proportion  of  one  of  Portland 
cement  to  two  of  clinker.  The  mass  of  clinker  and  cement,  after 
being  mixed,  is  passed  through  a  hydraulic  press  and  formed  into 
slabs  2  inches  in  thickness,  and  are  used  for  footpath  paving  under 
the  name  of  "Destructor"  concrete. 

4501.  Cork. — Pavements  made  from  granulated  cork  mixed  with 
asphalt  and  other  cohesive  substances  are  employed  in  London  and 
other  European  cities  to  deaden  the  noise  in  the  neighborhood  of 
hospitals  and  churches.  The  ingredients  are  compressed  into 
blocks  measuring  9  by  4^  by  2  inches.  The  blocks  are  imbedded  in 
tar  and  rest  upon  a  concrete  foundation  6  inches  thick.  The  cost 
per  square  yard  (32  blocks),  including  jointing  material,  but  exclu- 
sive of  laying  and  foundation,  is  about  $2.50. 

It  is  claimed  that  as  a  paving  material  it  is  non-absorbent,  non- 
slippery,  practically  noiseless,  more  durable  than  wood,  perfectly 
sanitary,  and  not  subject  to  expansion  and  contraction. 

Blocks  which  have  been  under  traffic  for  a  number  of  years 
seem  to  have  come  through  the  ordeal  with  a  satisfactory  result 
which  the  name  of  the  material  would  hardly  suggest. 

450m.  Copper  Slag. — Paving-bricks  are  made  in  Germany  from 
copper  slag.  The  slag  is  run  into  heated  cast-iron  moulds  having 
a  capacity  of  36  bricks;  immediately  after  filling  the  moulds  and 
their  contents  are  thickly  covered  with  sand  and  allowed  to  stand 
undisturbed  for  seventy-two  hours.  When  thoroughly  cooled  each 
brick  is  struck  a  strong  blow  with  a  hammer,  and  those  containing- 
blow-holes  crack. 

450n.  Steel  Trackways. — The  experimental  pieces  of  these 
trackways  which  have  been  constructed  consist  of  two  parallel 
lines  of  steel  plates,  eight  inches  wide,  laid  at  a  sufficient  distance 
apart  to  receive  the  wheels  of  vehicles  of  the  standard  gauge.  The- 
plates  are  provided  on  one  edge  with  a  flange  one-half  inch  wide, 
and  on  the  under  side  with  a  flange  about  6  inches  deep,  which, 
when  bedded  in  the  earth  of  the  roadway,  supports  the  rail  without 
the  use  of  cross-ties.  Tie-rods  are  used  at  intervals  of  about  10 
feet. 


MISCELLANEOUS   PAVEMENTS. 


317 


The  advantages  claimed  for  this  style  of  road  by  its  advocates 
are:  1.  That  it  can  be  built  without  greater  cost  in  most  cases,  and 
probably  with  less  cost  in  many  cases,  than  any  other  hard  and 
durable  road ;  2.  That  it  will  last  many  times  as  long  as  any  other 
known  material  for  road  purposes,  and  with  much  less  repair;  3. 
That  the  power  required  to  move  a  load  over  the  steel  trackway  is 
only  a  small  fraction  of  the  power  required  to  move  the  same  load 
over  any  other  kind  of  road. 


FIG,  3 2A.— CROSS-SECTION  OF  STEEL  TRACKWAY, 

During  1892  a  steel  trackway  was  constructed  between  Valen- 
cia and  Grao,  Spain,  at  a  cost  of  $28,518.  It  is  traversed  daily  by 
an  average  of  3200  vehicles,  each  of  which  pays  a  toll  of  about 
eight-tenths  of  a  cent.  The  annual  cost  of  maintenance  is  about 
$380.  The  trackway  replaces  a  stone  road  which  cost  $5470  a  year 
to  maintain. 

450o.  India  Rubber  in  large  sheets  about  1  inch  in  thickness  has 
been  tried  at  Hanover,  and  is  said  to  be  an  excellent  paving  ma- 
terial. A  small  sample  has  been  in  use  at  the  entrance  to  the  Eus- 
ton  Railroad  Station,  London,  for  about  14  years,  during  which 
period  the  cost  of  repairs  has  been  small.  The  sheets  are  laid  upon 
a  concrete  foundation,  and  are  held  down  by  strips  of  iron  which 
clasp  the  edges  tight  upon  each  side.  It  seems  to  meet  nearly  all 
the  requirements  of  a  perfect  paving  material,  being  exceedingly 
durable,  not  slippery,  and  absolutely  noiseless  and  impervious.  Its 
cost,  however— about  $34  per  square  yard— prohibits  its  general  use. 

45 Op.  Artificial  Paving-stones  are  manufactured  in  Germany 
from  a  mixture  of  coal-tar,  sulphur,  chlorate  of  lime,  glass  or  fur- 
nace slag.  The  process  employed  is  to  mix  the  tar  and  sulphur  at 
a  moderate  temperature,  and  to  this  mixture  add  the  chlorate  oT 
lime.  The  mixture  is  allowed  to  cool,  then  broken  into  small  frag- 
ments and  mixed  with  fragments  of  glass  or  blast-furnace  slag. 


318  HIGHWAY   CONSTRUCTION. 

This  mixture  is  heated  to  a  moderate  temperature,  placed  in 
moulds  of  the  desired  form,  and  subjected  to  a  pressure  of  about 
3000  pounds  per  square  inch.  The  specific  weight  of  the  stone  i& 
2.20,  and  the  resistance  to  crushing  315  pounds  to  the  square  centi- 
metre; the  resistance  to  wear  and  tear  in  use  is  said  to  be  half  as 
great  as  that  of  Swedish  granite. 

The  advantages  claimed  are :  Durability  equal  to  that  of  many 
stone  roads;  resistance  to  changes  of  temperature;  a  roughness 
of  surface  which  gives  horses  a  good  foothold;  non-transmission 
of  sound;  facility  of  cleansing  on  account  of  the  closeness  of  the 
joints. 

450q.  Asphaltina  is  a  patented  material  composed  of  coal-tar,, 
resin,  and  sulphur. 

450r.  Asphalt-granite  Pavement. — In  this  pavement  the  binder 
is  laid  on  a  concrete  foundation  in  the  ordinary  manner,  and  while 
it  is  still  soft  fragments  of  granite  or  other  hard  stone,  broken  to  a 
roughly  pyramidal  shape,  are  imbedded  in  the  asphalt  with  their 
points  upward,  and  just  below  the  level  of  the  surface  of  the 
finished  pavement.  The  final  layer  of  asphalt  is  put  on  over  these 
stones  and  fills  the  interstices  between  them,  and  appears  as  smooth 
as  an  ordinary  pavement.  The  object  of  this  construction  is  to 
render  the  pavement  non-slippery. 


CHAPTER  IX. 
FOUNDATIONS. 

451.  THE  stability,  permanence,  and  maintenance  of  any  pave- 
ment depends  upon  its  foundation.     If  the  foundation  is  weak,  the 
surface  will  quickly  settle  unequally,  forming  depressions  and  ruts. 
With  a  good  foundation  the  condition  of  the  surface  will  depend 
upon  the  material  employed  for  the  pavement  and  the  manner  of 
laying  it. 

452.  The  essentials  necessary  to  the  forming  of  a  good  founda- 
tion are: 

(1)  The  entire  removal  of  all  vegetable,  perishable,  and  yielding 
matter.     It  is  of  no  use  to  lay  good  material  on  a  bad  substratum. 

(2)  The  drainage  of  the  subsoil  wherever  necessary.     A  perma- 
nent foundation  can  only  be  secured  by  keeping  it  dry;  for,  where 
water  is  allowed  to  pass  into  and  through  it,  its  weak  spots  will  be 
quickly  discovered  and  settlement  will  take  place. 

(3)  The  thorough  compacting  of  the  natural  soil  by  rolling  with 
a  roller  of  proper  weight  arid  shape  until  it  forms  a  uniform  and 
unyielding  surface. 

(4)  The  placing,  on  the  natural  soil  so  compacted  a  sufficient 
thickness  of  an  impervious  and  incompressible  material  which  will 
effectually  cut  off  all  communication  between  the  soil  and  the  bot- 
tom of  the  pavement. 

453.  The  character  of  the  natural  soil  over  which  the  roadway 
is  to  be  built  has  an  important  bearing  upon  the  manner  of  forming 
and  the  kind  of  foundation;  each  class  of  soil  will  require  different 
treatment.    Whatever  its  character,  it  must  be  brought  to  a  dry  and 
tolerably  hard   condition   by  draining   and   rolling.      Sands   and 
gravels  which  do  not  hold  water  present  no  difficulty  in  secu  ring  a 
solid  and  secure  foundation;  clays  and  soils  retentive  of  water  are 
the  most  difficult.     Clay  should  be  excavated  to  a  depth  of  at  least 
18  inches  below  the  surface  of  the  finished  covering,  and  the  space 

319 


320  HIGHWAY    CONSTRUCTION. 

so  excavated  filled  in  with  sand,  furnace-slag,  ashes,  coal-dust, 
oyster-shells,  broken  brick,  or  other  materials  which  are  not  exces- 
sively absorbent  of  water.  Whichever  of  these  materials  is  used,  it 
should  be  thoroughly  consolidated  before  laying  the  pavement. 

In  ground  saturated  with  water  a  foundation  may  be  formed  of 
logs  or  layers  of  fascines;  but  unless  the  nature  of  the  ground  is 
such  as  will  always  insure  the  timber  being  kept  in  a  wet  or  damp 
state,  it  will  soon  rot  and  the  road  will  go  to  pieces.  Therefore  they 
should  never  be  employed  unless  under  unavoidable  circumstances. 

454.  Sand. — Sand  and  planks,  gravel,  and  broken  stone  have 
been  successively  used  to  form  the  foundation  for  pavements;  but 
although  eminently  useful  materials,  their  use  for  this  purpose  has 
been  and  always  must  prove  a  failure.     They  are  inherently  weak 
and  possess  no  cohesion,  and  the  main  reliance  both  for  strength 
and  wear  must  be  placed  upon  the  surface-covering.     This  cover- 
ing, being  usually  (except  in  case  of  sheet  asphalt)  composed  of 
small  units  with  joints  between  them  varying  from  one  half  to  one 
and  a  half  inches  possesses  no  elements  of  cohesion,  and  under  the 
blows  and  vibrations  of  traffic  the  independent  units  or  blocks  will 
settle  and  be  jarred  loose.    They  are  porous  and  the  subsoil  quickly 
becomes    saturated    with    urine    and    surface-waters    percolating 
through  the  joints;  winter  frosts  upheave  them  and  the  surface  of 
the  street  becomes  blistered  and  broken  up  in  dozens  of  places. 
The  defects  of  plank  foundations  are  stated  in  Art.  186. 

Although  sand,  gravel,  etc.,  by  themselves  are  unsuitable  as 
foundation  materials  for  block  pavements,  st^ll  when  used  with 
judgment  they  form  excellent  foundations  for  broken-stone  roads. 

455.  Sand  Foundation. — The  natural  soil  having  been  trimmed 
and  thoroughly  compacted  by  rolling  to  the  cross-section  which  is 
to  be  given  to  the  covering,  a  layer  of  sand  four  inches  thick  is 
spread  uniformly,  thoroughly  wetted  by  sprinkling,  and  rolled; 
two  other  layers  of  four  inches  each  are  in  like  manner  added  and 
rolled.   The  compression  effected  by  a  roller  weighing  ten  tons  will 
r.educe  the  thickness  of  twelve  inches  to  eight  a  greater  final  thick- 
ness than  this  is  unnecessary  unless  the  natural  soil  is  very  yield- 
ing, when  it  may  be  increased  to  twelve  or  sixteen  inches. 

456.  Blast-furnace   Slag. — The   ordinary  brittle  slag  makes  a 
very  good  foundation  for  a  road,  particularly  on  clay  or  wet  soils, 
as  by  rolling  the  top  pieces  form  a  powder  that  fills  the  interstices 


FOUNDATIONS.  321 


between  the  lower  fragments  so  thoroughly  that  neither  clay  nor 
mud  can  work  up  through  the  layer,  and  on  this  the  more  durable 
wearing  materials  can  be  placed.  It  was  found  impossible  to  form 
.any  roads  on  the  soft  clay  surface  of  the  Centennial  Fair  grounds 
at  Philadelphia  until  their  beds  had  been  prepared  by  a  layer  of 
well-rolled  furnace-slag,  after  which  they  stood  heavy  teaming 
without  under-drainage ;  the  binding  of  the  fragments  of  slag  with 
the  thorough  filling  of  the  interstices  preventing  any  mud  from 
working  up  through  the  first  or  cover  layer,  thus  keeping  the  road 
from  breaking  up. 

457.  Concrete. — As  a  foundation  for  all  classes  of  pavement 
(broken  stone  excepted)  hydraulic-cement  concrete  is  superior  to 
any  other.    When  properly  constituted  and  laid  it  becomes  a  solid 
coherent  mass  capable  of  bearing  great  weight  without  crushing, 
and  which  if  it  fail  at  all  must  fail  altogether.     It  is  the  most 
costly,  but  this  is  balanced  by  its  permanence  and  saving  in  the 
cost  of  repairs  to  the  pavement  which  it  supports.     It  admits  of 
access  to  subterraneous  pipes  with  less  injury  to  the  neighboring 
pavement  than  any  other,  for  the  concrete  may  be  broken  through 
at  any  point  without  unsettling  the  foundation  for  a  considerable 
distance  around  it,  as  is  the  case  with  sand  or  other  incoherent 
material ;  and  when  the  concrete  is  replaced  and  set,  the  covering 
may  be  reset  at  its  proper  level  without  the  uncertain  allowance  for 
settlement  which  is  necessary  in  other  cases. 

458.  Thickness  of  Concrete. —  The  thickness  of  the  concrete  bed 
must  be  proportioned  by  the  engineer;  it  should  be  sufficient  to 
provide  against  breaking  under  transverse  strain  caused  by  the  set- 
tlement of  the  subsoil.     On  a  well-drained  soil  six  inches  will  be 
found  sufficient,  but  in  moist  and  clayey  soils  twelve  inches  will 
not  be  excessive.    On  such  soils  a  layer  of  sand  or  gravel,  spread  and 
compacted  before  placing  the  concrete,  will  be  found  very  bene- 
ficial. 

459.  Concrete   (called   beton    by  the   French  engineers)   is  a 
species  of  artificial  stone  composed  of  (1)  the  matrix,  which  may 
be  either  lime  or  cement  mortar,  usually  the  latter,  and  (2)  the 
aggregate,  which  may  be  any  hard  material,  as  gravel,  shingle, 
broken  stone,  shells,  brick,  slag,  etc. 

The  essential  quality  of  concrete  seems  to  be  that  the  material 
of  the  aggregate  should  be  of  small  dimensions,  so  that  the  cement- 


322  HIGHWAY    CONSTRUCTION. 

ing  medium  may  act  in  every  direction  round  them,  and  that  the 
latter  should  on  no  account  be  more  in  quantity  than  is  necessary 
for  that  purpose.  The  aggregate  should  be  of  different  sizes,  so 
that  the  smaller  shall  fit  into  the  voids  between  the  larger.  This 
requires  less  mortar  and  with  good  aggregate  gives  a  stronger  con- 
crete. Broken  stone  is  the  most  common  aggregate. 

It  is  usual  to  require  that  the  stone  shall  be  broken  so  as  to 
pass  any  way  through  a  2-inch  ring.  To  insure  compact  packing 
the  aggregate  should  consist  of  a  mixture  of  broken  stone  ranging 
from  1  to  3  inches,  and  pebbles  which  are  at  least  equal  to  the 
strength  of  the  mortar.  Sun-dried  or  rain-soaked  material  is  to  be 
strictly  avoided.  The  choice  of  the  cementing  substance,  lime  or 
cement,  depends  upon  the  use  of  the  concrete. 

460.  The  strength  of  concrete  depends  upon  the  cohesion  of 
the  matrix,  adhesion  to  the  aggregates,  irregular  bonding  or  inter- 
locking of  the   coarser   fragments,   and   upon   the   strength   and 
proportion  of  each  ingredient. 

Concrete  for  pavement  foundations  should  be  dense  and  homo- 
geneous, with  the  voids  of  the  aggregate  thoroughly  filled  with 
mortar,  and  the  latter  must  again  be  so  constituted  that  the  voids 
between  the  grains  of  sand  shall  be  closely  filled  by  the  cement 
paste. 

Good  concrete  has  a  specific  gravity  of  1.5  to  2.5,  according  to 
its  composition  of  crushed  bricks  or  heaviest  stones.  A  cubic  yard 
weighs  from  2500  to  3900  pounds.  V  / 

461.  Proportions, — The  proportions  of  the  ingredients  required 
for  the  manufacture  of  concrete  may  be  ascertained  by  measuring 
the  respective  voids. 

The  proportion  of  voids  may  be  determined  by  experiment  in 
either  of  the  ways  described  in  Art.  373,  page  207. 

The  voids  of  broken  stone,  in  which  the  size  and  shape  of  the 
pieces  are  nearly  uniform,  are  about  0.5  of  the  mass.  If  the  pieces 
are  not  uniform,  the  voids  are  about  0.4  of  the  mass.  The  voids  in 
gravel  vary,  but  average  about  0.5  of  the  mass. 

462.  The  voids  between  the  grains  of  sand  will  probably  average 
33  per  cent;  that  is  to  say,  67  per  cent  of  the  cubic  contents  tc/be 
occupied  by  the  mortars  are  absorbed  by  the  solids  of  the  grains  of 
sand  and  33  per  cent  are  to  be  filled  in  with  cement,  so  that  a 
mortar  of  one  part  of  cement  to  two  of  sand,  and  no  more,  is 


FOUNDATIONS.  333 


required  for  water-tight  work.  A  strong  water-tight  concrete 
will  contain  by  volumes  as  follows:  cement,  sand,  stone,  as 
1:2:5;  and  with  fine  Portland  this  mixture  may  reach  after 
four  weeks  a  compressive  strength  of  175  tons  per  square  foot. 
The  eight  volumes  of  material  fill  finally  a  space  of  about  5.2 
volumes. 

463.  The   addition   of  water   must   be   limited   to   the  actual 
requirements,  which  fluctuate  for  natural  cements  between  50  and 
55  per  cent,  and  for  Portland  cement  between  40  and  45  per  cent, 
of  the  weight  of  the  cement  used.     Plasticity  is  only  to  be  attained 
by  diligently  tamping  an  apparently  dry  mass  until  water  appears 
on  the  surface. 

464.  The  following  are  some  of  the  more  usual  proportions : 

American  hydraulic  cement 1  part 

Sand. , , 2  parts 

Broken  stone , 3     " 

Portland  cement 1  part 

Sand 3  parts 

Broken  stone ; 5  to  7     " 

Portland  cement 1  part 

Sand 2£  parts 

Gravel 3 

Broken  stone  5      " 

Tests  of  this  formula  showed  a  filling  of  voids  within  6$  of  the- 
whole  volume.  One  barrel  of  cement  weighing  380  pounds  net  made 
1.18  cubic  yards  of  concrete  weighing  when  dry  136  pounds  per 
cubic  foot.  Cost  per  cubic  yard,  $6. 

For  one  cubic  yard  of  concrete  of  stone,  gravel  and  sand,  with- 
out voids,  the  following  quantities  of  materials  are  required : 

Broken  stone  50$  of  its  bulk  voids 1.00    cubic  yard 

Gravel  to  fill  voids  in  the  stone 50        "        " 

Sand        "        "        "      gravel 25 

Cement    "        "        "      sand 125      " 

For  one  cubic  yard  of  concrete  of  stone  and  sand  without  voids, 
tke  following  quantities  of  materials  are  required : 

Broken  stone  50$  of  its  bulk  voids 1.00  cubic  yard 

Sand  to  fill  voids  in  the  stone 50      " 

Cement"       "         "      sand 25      " 


324  HIGHWAY   CONSTRUCTION. 

465.  Mixing. — The  concrete  may  be  mixed  by  hand  or  by  ma- 
chinery.    In  the  first  method  the  cement  and  sand  are  mixed  dry. 
About  half  the  sand  to  be  used  in  a  batch  of  concrete  is  spread 
evenly  over  the  mortar  board,  then  the  dry  cement  spread  evenly 
over  the  sand,  and  then  the  remainder  of  the  sand  is  spread  on  top 
of  the  cement.     The  sand  and  cement  are  then  mixed  with  a  hoe 
or  by  turning  and  re-turning  with  a  shovel.     It  is  very  important 
that  the  sand  and  cement  be  thoroughly  mixed,     A  basin  is  then 
formed  by  drawing  the  sand  and  cement  to  the  outer  edges  of  the 
box',  and  the  water  is  poured  into  it.     The  sand  and  cement  are 
then  thrown  back  upon   the  water,  the  whole  mass  thoroughly 
mixed  with  the  hoe  or  shovel,  and  then  levelled  off.     The  broken 
stone  should  be  sprinkled  with  sufficient  water  to  remove  all  dust 
and  thoroughly  wet  the   entire   surface.     The   amount   of   water 
required  will  vary  considerably  with  the  absorptive  power  of  the 
stone  and  the  temperature  of  the  air.     The  wet  stone  is  then  to  be 
spread  evenly  over  the  top  of  the  mortar,  and  the  whole  mass 
thoroughly  mixed  by  turning  up  with  a  shovel.     When  the  aggre- 
gate consists  of  broken  bricks  or  other  porous  material  it  should  be 
thoroughly  wetted  and  time  allowed  for  absorption  previous  to  use; 
otherwise  it  will  take  away  part  of  the  water  necessary  to  effect 
the  setting  of  the  cement. 

466.  Laying. — After  mixing,  the  concrete  is  conveyed  in  wheel- 
barrows and  compacted  in  position  by  ramming  in  layers.     When 
the  thickness  is  to  be  6  inches  it  should  be  laid  in  one  layer;  if 
thicker,  in  two  equal  layers,  the  surface  of  the  first  layer  being 
moistened  before  spreading  the  second.     If  too  much  water  has 
been  used  in  mixing,  it  will  be  impossible  to  compact  it  by  ram- 
ming.    When  ready  for  use  the  concrete  should  be  quite  coherent 
and  capable  of  standing  at  a  steep  slope]  without  the  water  running 
from  it.     Ramming,  when  properly  done,  consolidates   the  mass 
about  5  or  6  per  cent,  rendering  it  less  porous,  and  very  materially 
stronger.,     The  rammers  are,  like  those  used  in  street-pav\ng,  ®f 
wood,  about  4  feet  long,  6  to  8  inches  in  diameter  at  foot,  with  a 
lifting-handle,  and  shod  with  iron;  weight  about  35  pounds.     They 
are  let  fall  six  or  eight  inches.     The  men  using  them,  if  standing 
on  the  concrete,  should  wear  india-rubber  boots  to  protect   their 
feet  from  corrosion  by  the  cement. 

The  ramming  should  be  continued  only  until  the  water  begins 


FOUNDATIONS.  325 


to  ooze  out  on  the  upper  surface.  Too  severe  or  long-continued 
pounding  injures  the  strength  of  the  concrete  by  forcing  the  broken 
stone  to  the  bottom  of  the  layer,  and  by  disturbing  the  incipient  set 
of  the  cement.  When  the  concrete  is  rammed,  walking  should  not 
be  permitted  on  it  for  at  least  12  hours;  24  would  be  better.  It  is 
necessary  to  give  the  concrete  abundance  of  time  to  dry  and  set. 
This  precaution  is  indispensable.  If  an  undue  amount  of  moisture 
should  remain  after  the  superstructure  is  laid,  it  will  destroy  the 
homogeneous  qualities  of  the  concrete. 

487.  A  correctly  proportioned  concrete  has  fully  as  much 
strength  as  the  cement-mortar  used  in  mixing  it.  By  diminishing 
the  aggregate  below  the  calculated  quantity  the  cost  of  concrete  is 
increased  without  benefit  to  strength. 

The  transverse  strength  of  concrete  ranges  between  50  and  400 
pounds,  depending  upon  the  character  of  the  Dement  and  skilful- 
ness  of  manipulation. 

468.  Compressive  Strength.— Trautwine  says  that  cubes  of  Port- 
land cement,  sand,  and  broken  stone,  "  well  made  and  rammed, 
should,  either  in  air  or  in  water,  require  to  crush  them  at  different 
ages  not  less  than  about  as  follows : 

Ageiu  months 1          3          6          9          12 

Tons  per  square  foot 15        40        65        85        100 

Under  favorable  conditions  of  materials,  workmanship,  and  weather, 
the  strengths  may  be  from  50  to  100  per  cent  greater." 

The  compressive  strength  of  6-inch  cubes  of  concrete  exposed 
to  the  air  for  six  months,  as  determined  in  connection  with  the 
construction  of  the  St.  Louis  Bridge,  was  as  follows:  with  the 
proportions  of  1  part  cement  (Akron  and  Louisville),  1  part  sand, 
and  4  parts  broken  limestone,  the  mean  compressive  resistance  for 
nine  trials  was  1200  pounds  per  square  inch  (85  tons  per  square 
foot) ;  and  with  the  proportions  of  1,  2,  4,  respectively,  the  average 
resistance  for  twelve  trials  was  940  pounds  per  square  inch  (70  tons 
per  square  foot). 

Tests  with  the  United  States  testing-machine  at  Watertown, 
Mass.,  between  steel  gave  an  average  of  1544  pounds  per  square 
inch  (110  tons  per  square  foot)  for  4-inch  to  6-inch  cubes  of  con- 
crete 46  months  old  composed  of  1  part  Kosendale  cement-paste, 
1}  parts  sand,  and  6  parts  broken  stone.  Under  the  same  condi- 


326 


HIGHWAY    CONSTRUCTION. 


tions,  concrete  composed  of  1  part  Roseudale  cement-paste,  3  parts 
sand,  and  G  parts  broken  stone  stood  1021  pounds  per  square  inch 
(73  tons  per  square  foot).  Another  sample  of  cement  gave  1078 
pounds  per  square  inch  (77  tons  per  square  foot)  for  concrete  2.2 
months  old  composed  of  1  part  cement  paste,  3  parts  sand,  and  4 
parts  broken  stone.  Ten  experiments  with  a  single  sample  of 
Portland  cement  gave  3067  pounds  per  square  inch  (219  per  square 
foot)  for  concrete  composed  of  1  part  cement  paste,  3  parts  sand, 
and  6  parts  broken  stone.  The  concrete  under  the  Washington 
monument,  composed  of  1  part  Portland,  2  parts  sand,  3  parts  peb- 
bles, and  4  parts  broken  stone,  when  six  months  old  stood  2000 
pounds  per  square  inch  (144  tons  per  square  foot). 

Experiments  made  in  connection  with  the  construction  of  the 
Vyrnwy  dam — built  to  impound  water  for  the  supply  of  Liverpool, 
England — gave  an  average  strength  from  six  experiments,  for  cubes 
of  mortar  composed  of  1  part  Portland  cement  and  2  parts  of  sand 
from  32  to  37  months  old,  crushed  between  pine  cushions  |  inch 
thick,  of  4428  pounds  per  square  inch  (284.7  tons  per  square  foot) ; 
and  cubes  of  concrete  composed  of  gravel  and  sufficient  mortar  com- 
posed as  above  to  fill  the  interstices  gave  an  average  strength,  for 
two  cubes  35  and  36  months  old,  of  3497  pounds  per  square  inch 
(224.9  tons  per  square  foot).  The  blocks  were  made  from  the  con- 
crete actually  used  in  the  work,  and  were  moulded  by  ordinary  work- 
men without  supervision,  with  the  intention  of  securing  blocks  repre- 
sentative of  the  concrete  as  laid  in  the  work.  For  cubes  of  the  con- 
crete tested  between  "  mill-boards  "  (straw-boards)  the  same  series 
of  experiments  gave  results  as  follows: 


Age  of  the  Blocks. 
Months. 

Number  of 
Experiments. 

Mean  Crushing  Strength. 

Lbs.  per  sq.  in. 

Tons  per  sq.  ft. 

32-36 

3 

2,365 

170.4 

20-30 

6 

2,278 

164.0 

5-8 

2 

1,742 

125.5 

1-2* 

7 

1,477 

106.4 

469.  Cost. — The  cost  of  concrete  varies  greatly,  depending  upon 
the  kind   of   mortar,  whether  lime  or  cement;  upon  the  richness 


FOUNDATIONS.  327 


of  the  mortar;  upon  the  proportion  of  aggregate  to  mortar,  upon 
the  cost  of  the  ingredients  and  of  the  labor,  etc. 

It  varies  from  $4.00  to  $6.00  per  cubic  yard  with  Rosendale 
cement,  and  from  $6.00  to  $9.00  per  cubic  yard  with  the  Portland 
cement.  The  cost  for  pavement  foundations  ranges  from  94  cents 
to  $1.50  per  square  yard. 

PORTLAND-CEMENT  CONCRETE. 
Proportions : 

Cement 1  part 

Sand 3  parts 

Broken  stone. 5    " 

Portland  cement 1.28  bbls.     at  $2.60  —  $3.33 

Sand O.SOcn.yd."      1.30  =  0.65 

Broken  stone 0.90       "       '       1.23  =  1.12 

Labor 0:91  day       "      1.75  =  1.59 

Foreman 0.07    "         "      300  =  0.21 

Total  cost  of  one  cubic  yard  in  place $6.90 

470.  An  excellent  concrete  is  made  of  80  parts  of  furnace-slag 
(crushed)  and  20  parts  of  asphaltic  cement;  the  slag  and  cement 
should  be  heated  before  mixing,  and  be  laid  while  hot. 

471.  As  the  value  of  concrete  depends  principally  upon  the  ma- 
trix or  cementing  medium,  a  thorough  knowledge  of  the   mortar 
and  the  characteristics  of  its  ingredients  is  indispensable  for  suc- 
cessful manipulation. 

The  material  employed  for  the  manufacture  of  mortar  are : 

(1)  Lime  (common  and  hydraulic). 

(2)  Hydraulic  cements  (natural  and  artificial). 

(3)  Sand. 

472.  Common  Lime    is   derived   from  the  calcination  of  pure 
and  impure  limestones,  and  is  extensively  employed  for  the  manu- 
facture of  mortar  used  in  building  construction.     It  is  unsuitable  for 
ihe  manufacture  of  concrete.     Concretes  in  which  it  is  used  as  a 
matrix  are  permeable,  weak,  and  liable  to  rupture  from  sudden 
shock.     Lime  mortar  sets  or  hardens  slowly,  and  if  deprived  of  air 
setting  may  never  take  place,  as  it  hardens  mainly  through  the  aid 
of  carbonic  acid  gas,  which  it  absorbs  slowly  from  the  atmosphere. 

Hydraulic  Lime  is  in  many  respects  similar  to  common  lime, 
but  possesses  the  property  of  hardening  under  water.  This  class  of 


328  HIGHWAY   CONSTRUCTION. 

lime  is  much  used  in  Europe,  but  there  is  none  produced  in  the 
United  States. 

473.  Hydraulic  Cement  is  of  two  classes,  natural  and  artificial. 
The  American  natural  or  Rosendale  type  of  cement  is  made  by 
burning  in  ordinary  draw-kilns  cement  rock  composed  of  limestone 
intimately  mixed  with  silica,  alumina,  magnesia,  etc.,  and  grinding 
the  calcined  product  to  powder.  The  cement  thus  produced 
depends  for  its  uniformity  upon  the  homogeneity  of  the  rock  from 
which  it  is  made. 

These  cements  are  of  a  porous,  globular  texture,  with  a  specific 
gravity  of  about  2.7.     They  do  not  heat  up  nor  swell  sensibly  whilst 
they  are  mixed;  they  set  quickly  in  air,  but  harden  slowly  under 
water,  without  shrinking,  and  attain  great  strength  with  well -de 
veloped  adhesive  force. 

Color. — The  color  of  these  cements  gives  no  clue  to  their  ce- 
mentitious  value,  since  it  is  chiefly  due  to  oxides  of  iron  and  man- 
ganese, which  bear  no  direct  relation  to  the  hydraulic  properties. 

To  insure  efficient  chemical  action  in  hardening,  the  grinding 
must  be  carried  to  the  production  of  impalpable  powder.  These 
cements  bear  admixture  of  sand  to  double  their  own  volume  and 
over.  For  mixing  pure  cements  from  30  to  40  per  cent  of  water 
must  be  added. 

Many  American  cements  of  this  class  contain  large  percentages 
of  carbonate  of  magnesia.  Pure  carbonate  of  magnesia,  when 
burned  at  a  moderate  heat,  ground  to  fine  powder,  and  made  into- 
paste  with  sea-water,  makes  a  cement  which  is  superior  in  hardness 
and  strength  to  any  other,  not  excepting  even  Portland  cement. 
These  cements  give  good  adhesion  to  stones  and  bricks,  because 
they  part  with  their  surplus  water  more  slowly  than  the  others. 
Whenever  judiciously  selected  and  conscientiously  manipulated 
they  have  given  full  satisfaction.  Many  causes  co-operate  in  affect- 
ing rocks  of  the  compound  character  required  for  the  production  of 
hydraulic  cements.  Deleterious  material  is  disseminated  through 
the  various  strata  of  a  quarry  in  constantly  and  widely  changing 
proportions,  each  stratum  exhibits  heterogeneous  features.  Hence 
it  taxes  judgment,  begotten  of  large  experience,  honesty,  careful- 
ness, and  skill,  to  keep  up  reasonably  uniform  quality. 

Different  quarries  show  dissimilar  stones.  The  best  brands  vary 
greatly  in  chemical  composition.  Fineness,  density,  thorough  and 


FOUNDATIONS.  329 


homogeneous  mixture,  humidity,  accessory  ingredients,  enter  largely 
into  the  problems. 

To  preserve  the  activity  and  strength  of  the  natural  cements, 
air  and  moisture  must  be  excluded  by  careful  packing  and  dry 
storage  of  the  barrels;  otherwise  the  premature  development  of 
carbonate  of  lime  will  interfere  with  the  subsequent  hydration. 

Prof.  DeSmedt  found  for  our  native  Virginia  cements  in  pure 
state,  after  30  days'  exposure,  170  to  250  pounds  tensile  strength 
per  square  inch,  which  increased  in  11  months  to  316  to  381  pounds. 
Mixed  with  equal  proportions  of  sand  he  obtained  from  116  to  155 
pounds  and  180  to  190  pounds  as  above. 

Gillmore  states  the  adhesion  of  Rosendale  cement  to  front  bricks, 
after  28  days,  when  pure  to  be  30  pounds,  and  when  mixed  with 
one  or  two  parts  of  sand  16  and  12  pounds. 

Clarke  reports  the  tensile  strength  of  these  Rosendale  cements, 
pure,  after  one  and  twelve  months,  as  145  and  290  pounds  respect- 
ively; when  mixed  1  to  1,  to  116  and  256  pounds;  when  mixed  1  to 
2,  60  and  180  pounds ;  and  when  mixed  1  to  3,  35  and  121  pounds 
after  the  same  periods. 

One  cubic  foot  of  Rosendale  cement  weighs  49  to  59  pounds. 
The  proportion  of  tensile  to  compressive  strength  averages  probably 
after  a  month  1  to  4,  and  rises  after  two  years  about  1  to  6  or  ?. 

The  specifications  of  the  Engineers'  Department  of  the  District 
of  Columbia  require  seven  days  after  mixture,  for  neat,  natural 
cement,  95  pounds,  and  for  mixtures  with  one  and  two  parts  of  sand 
56  and  22  pounds  tensile  strength  per  square  inch,  respectively.  The 
gradual  increase  of  strength  by  time  is  carefully  noted  and  estab- 
lishes the  reputation  of  the  accepted  brands. 

474.  Natural  Portland  Cement. — Portland  cement   derives  its 
name  from  the  resemblance  which  hardened  mortar  made  of  it 
bears  to  a  stone  found  in  the  isle  of  Portland,  off  the  south  coast  of 
England.     It  is  manufactured  in  those  rare  cases  where  rocks  are 
traced  which  contain  combinations  of  lime  and  silica  of  alumina  in 
the  chemical  proportions  and  physical  condition  found  necessary 
for  producing  artificial  Portland. 

The  treatment  then  differs  from  that  of  ordinary  cement  only 
in  the  higher  temperature  for  burning.  There  are  extensive  works 
of  this  class  around  Perlmoos  in  Germany,  Grenoble  in  France,  etc. 

475.  Artificial  Portland  Cement  —Fully  95  per  cent  of  all  the 


330  HIGHWAY    CONSTRUCTION. 

Portland  cement  used  at  the  present  day  is  artificial.  It  is  made 
by  thoroughly  mixing  together,  in  suitable  proportions,  clay  and 
finely  pulverized  carbonate  of  lime  (either  chalk,  marl,  or  compact 
limestone),  burning  the  mixture  in  kilns  at  a  high  temperature,  and 
then  grinding  the  burned  product  between  ordinary  millstones.  The 
result  is  an  impalpable,  dense,  drossy,  steel-hard  powder,  having  a 
specific  gravity  of  3.0  to  3.15.  A  few  weeks'  storage  seasons  the 
powder  and  makes  it  ready  for  use. 

As  accessory  ingredients,  sulphate  of  lime  and  other  combinations 
of  sulphur  occur  in  Portland  cement,  which,  combining  with  seven 
chemical  equivalents  of  water,  and  even  more,  cause  considerable 
increase  of  volume.  This  explains  why  a  large  percentage  of  sul^ 
phuric  acid  endangers  the  durability  of  hydraulic  cements,  while  a 
small  addition  of  it  tends  to  increase  their  strength. 

If  the  contents  of  clay  in  Portland  cement  rise  above  50  pet 
centum  of  the  calcined  lime  (overclayed  cement),  complete  vitrifica- 
tion is  to  be  feared  during  the  burning;  the  lack  of  cementing  sub- 
stance (lime)  is  felt,  and  the  cement  becomes  an  inert  mass  unfit 
for  use.  On  the  other  hand,  an  "  overtimed  "  cement  tends  toward 
quick  setting  and  blowing  or  expansion.  These  effects,  due  to  the 
presence  of  free  caustic  lime,  may  be  remedied  by  airing  such 
cement  for  a  day  or  more,  when  the  caustic  lime  will  absorb  car- 
bonic acid  from  the  air  and  become  a  neutral  body  for  the  cement. 
There  is  for  each  material  one  most  favorable  proportion  in  which 
the  tendencies  to  shrinking  and  to  expanding  neutralize  each 
other,  so  that  a  good  cement  is  the  result. 

The  chemical  reactions  require  for  cement  burned  at  white  heat 
only  half  as  much  water  as  those  burned  at  moderate  heat;  this  no 
doubt  contributes  to  the  superior  strength  of  the  Portland.  Water 
in  the  proportion  of  20  to  25  per  cent  of  the  weight  of  the  cement 
generally  suffices  for  mixing  pure  cement.  Mixtures  with  sand,  ac- 
cording to  its  dry  or  moist  state,  require  increased  quantities.  By 
far  the  strongest  mortar,  with  or  without  sand,  results  from  mix- 
tures in  a  state  of  incoherent  dampness,  with  no  more  plasticity 
than  absolutely  necessary  for  the  work  in  hand. 

Too  long-continued  stirring  or  excess  of  water  prevents  setting, 
a  paste  being  formed  which  slowly  hardens  by  shrinkage,  caused 
by  evaporation  and  pressure,  analogous  to  fat  lime. 

Normal  material  and  treatment  result  in  slow  and  cool  setting 


FOUNDATIONS.  331 


"but  comparatively  low  adhesive  power.  The  tensile  strength  in- 
creases for  a  slow-setting  Portland  cement  gradually  for  about  two 
years,  while  the  compressive  strength  increases  for  many  years. 

All  Portland  cements  bear  the  admixture  of  large  quantities  of 
sand,  but  an  excess  retards  setting  and  reduces  the  tensile  strength. 
Mixtures  of  1,  2,  3,  and  4  parts  of  sand  to  one  part  of  cement 
showed  one  year  after  mixing  a  reduction  of  25,  50,  60,  and  70  per 
centum  (Michaelis  and  Grant's  tests).  An  excess  of  sand  makes  & 
harsh,  raw  mixture,  difficult  of  manipulation  and  hence  unsuitable 
for  architectural  work. 

Magnesia  as  a  prominent  ingredient  of  the  limestone,  used  as 
raw  material  for  producing  Portland  cement,  acts  badly,  even 
treacherously.  It  does  not  harden  hydraulically  either  with  silica 
or  with  alumina;  hence  it  remains  as  calcined  magnesia,  simply 
ballast,  which  lessens  the  quantity  of  hydraulic  substances.  Mixed 
with  water  it  forms  a  hydrate  of  no  high  cementitious  value.  The 
absorption  of  water  proceeds  the  slower  the  stronger  the  magnesia 
has  been  calcined.  In  consequence  the  hydration  takes  place  at  a 
time  when  the  hydraulic  hardening  of  Portland  cement  is  virtually 
completed,  and  the  swelling,  due  to  larger  masses  of  magnesia, 
causes  a  destruction  of  this  cohesion  already  attained,  and  this  has 
caused  the  collapse  of  bridges  and  buildings,  and  the  crumbling  of 
plastering  on  walls  in  France,  according  to  the  observations  of 
Lechartier,  Deville,  and  Calvert.  This  belated  increase  of  volume 
escapes  observation  under  the  ordinary  tests  for  expansion  and  re- 
quires special  caution.  Portland  cements  containing  more  than  5 
per  cent  of  magnesia  should  be  rejected. 

476.  Characteristics  of  Portland  Cement. 

Color. — The  color  should  be  a  dull  greenish  gray,  caused  by  the 
dark  ferruginous  lime  and  the  intensely  green  maganese  salts.  Any 
variation  from  this  color  indicates  the  presence  of  some  impurity: 
blue  indicates  an  excess  of  lime ;  dark  green,  a  large  percentage  of 
iron;  brown,  an  excess  of  clay;  a  yellowish  shade  indicates  an 
underburned  material. 

Fineness. — It  should  have  a  clear,  almost  floury  feel  in  the  hand ; 
a  coarse,  gritty  feel  denotes  coarse  grinding.  The  fineness  should 
be  such  that  80  per  cent  will  pass  through  a  sieve  of  2500  meshes 
to  the  square  inch. 

Weight.— -It  should  weigh  from  84  to  88  pounds  per  cubic  foot. 


332  HIGHWAY   CONSTRUCTION. 

A  cement  weighing  from  70  to  80  pounds  per  cubic  foot  is  invari- 
ably a  weak  one,  though  it  may  be  of  the  requisite  fineness;  at  the 
same  time  a  heavy  cement  if  coarsely  ground  is  also  weak  and  will 
have  no  carrying  capacity  for  sand. 

Light  weight  may  be  caused  by  laudable  fine  grinding,  or  by 
objectionable  underburning.  In  testing,  weight  and  fineness  must 
be  taken  in  conjunction. 

Specific  Gravity,  between  3  and  3.05.  As  a  rule  the  strength  of 
Portland  cement  increases  with  its  specific  gravity. 

Tensile  Strength. — When  moulded  into  a  briquette  and  placed 
in  water  for  seven  days  it  should  be  capable  of  resisting  a  tensile 
strain  of  from  300  to  400  pounds  per  square  inch. 

Setting. — A  pat  made  with  the  minimum  amount  of  water 
should  set  in  not  less  than  three  hours  nor  take  more  than  six 
hours. 

Expansion  and  Contraction. — Pats  left  in  the  air  or  placed  in 
water  should  during  or  after  setting  show  neither  expansion  nor 
contraction,  either  by  the  appearance  of  cracks  or  change  of  form. 

A  cement  that  possesses  the  foregoing  properties  may  be  con- 
sidered a  fair  sample  of  Portland  cement  and  would  be  suitable  for 
any  class  of  work. 

Portland  cement,  although  the  best  material  that  can  be  used  as 
a  cementing  medium,  should  not  be  used  by  any  one  who  is  not  pre- 
pared to  take  the  trouble  and  incur  the  trifling  expense  of  testing 
it;  because  if  manufactured  with  improper  proportions  of  its  con- 
stituents, or  improperly  burnt,  it  may  do  more  mischief  than  the 
poorest  lime. 

477.  Cement  Tests. — As  the  value  of  cements  varies  greatly  with 
their  physical  properties,  and  since  one  lot  of  cement  is  liable  to 
differ  very  much  from  another  lot  of  the  same  brand,  it  is  necessary, 
in  order  to  obtain  an  idea  of  their  relative  merits,  to  make  a  series 
of  tests  as  to  the  effect  that  the  amount  of  sand,  water,  temperature, 
pressure,  age,  etc.,  has  upon  them. 

How  to  carry  out  and  interpret  the  results  of  various  tests  of 
cements  involves  great  care  and  study  and  erroneous  conclusions 
may  be  arrived  at  when  undertaken  by  those  not  thoroughly  ac- 
quainted with  the  subject  and  with  the  particular  cements  to  be 
tested. 


FOUNDATIONS.  333 


478.  The  properties  of  a  cement  which  are  usually  examined  to 
determine  its  constructive  value  are  (1)  color,  (2)  weight,  (3)  activity, 
{4)  soundness,  (5)  fineness,  and  (6)  strength.     The  last  three  are  the 
most  important. 

479.  Color.— As  previously  stated,  the  color  of  American  natural 
cements  has  no  influence  upon   its  quality.     The  color  of  these 
cements  is  generally  brown,  ranging  from  very  light  to  dark  brown. 
Sometimes  a  very  light  color  indicates  an  inferior  or  underburned 
rock.     With  Portland  cement  it  is  different;  the  color  has  an  im- 
portant bearing  upon  its  quality;  it  should  be  dull  greenish  gray, 
and  any  deviation  from  this  indicates  impurities,  as  stated  in  Art. 
476. 

480.  Weight. — For   any  particular  cement  the  weight  varies 
with  the  degree  of  heat  in  burning,  the  degree  of  fineness  in  grind- 
ing, and  the  density  of  packing.     Other  things  being  the  same,  the 
harder-burned  varieties  are  the  heavier.     The   finer  a  cement  is 
ground  the  more  bulky  it  becomes,  and  consequently  the  less  it 
weighs. 

The  weight  per  unit  of  volume  is  usually  determined  by  sifting 
the  cement  into  a  measure  as  lightly  as  possible,  and  striking  the 
top  level  with  a  straight-edge.  In  careful  work  the  height  of  fall 
is  specified.  Since  the  cement  absorbs  moisture,  the  sample  must 
be  taken  from  the  interior  of  the  package.  The  weight  per  cubic 
ioot  is  neither  exactly  constant,  nor  can  it  be  determined  precisely; 
and  for  the  practical  purpose  of  the  user  is  of  very  little  service 
in  determining  the  value  of  a  cement.  However,  it  is  often  speci- 
fied as  one  of  the  requirements  to  be  fulfilled. 

481.  The  following  values,  determined  by  sifting  the  cement 
with  a  fall  of  three  feet  into  a  box  having  a  capacity  of  one  tenth 
of  a  cubic  foot,  may  be  taken  as  fair  average  for  ordinary  cements. 
The  difference  in  weight  for  any  particular  kind  is  mainly  due  to  a 
difference  in  fineness. 

Portland,  English  and  German 77  to  90  Ibs.  per  cu.  ft. 

' '          fine  ground  French 69 

"  American 95 

Roman 54 

Rosendale  49  to  56 

LimeofTeil.  50 


334  HIGHWAY   CONSTEUCTIOK. 

Since  a  bushel  is  1.244  cubic  feet,  the  weight  per  bushel  can 
be  approximately  obtained  by  adding  25  per  cent  to  the  above 
quantities.  However,  it  is  better  to  make  the  cubic  foot  the  standard 
unit  measure. 

482.  Activity. — A  mortar  is  said  to  have  set  when  it  has  at- 
tained such  a  degree  of  induration  that  its  form  cannot  be  altered 
without  causing  a  fracture,  i.e.,  when  it  has  entirely  lost  its  plas- 
ticity.    Some  cements  set  quickly,  while  others  are  comparatively 
slow  in  developing  the   first   indications   of  hydraulicity.      This 
property  is  called  hydraulic  quickness  or  activity.     A  quick-setting 
cement  is  especially  valuable  in  constructions  under  water. 

A  distinction  should  be  carefully  made  between  hydraulic  ac- 
tivity and  hydraulic  energy  or  strength.  The  former  refers  to  the 
time  required  to  attain  a  small  degree  of  strength,  and  the  latter  to 
the  amount  of  strength  ultimately  attained.  There  is  no  necessary 
relation  between  time  of  setting  and  ultimate  strength ;  but,  as  a, 
general  rule,  the  slow-setting  cements  ultimately  attain  to  a  greater 
strength  than  quick-setting  ones. 

The  activity  of  cement  may  be  increased  by  adding  a  quicker- 
setting  cement,  as  plaster  of  paris,  lime,  clay,  or  even  grease, — all 
such  ingredients,  particularly  the  last,  weakening  the  resulting 
mortar. 

483.  "  The  effects  of  a  variation  of  temperature  upon  the  hy- 
draulic   quickness  of  mortars — whether  derived    from   hydraulic 
cement,  a  mixture  of  common  lime  and  pozzuolana,  or  produced 
by  artificial  means — is  very  marked :  so  much  so,  indeed,  that  in  all 
comparative  tests  of  this  kind  it  is  important  to  adopt  some  fixed 
standard  of  temperature,  not  only  for  the  water  with  which  the 
cement  is  mixed,  as  well  as  that  in  which  the  cement  is  immersed, 
but  for  the  dry  ingredients  and  the  surrounding  atmosphere.     All 
cements  are  not  equally  sensitive  to  a  variation  of  temperature/'7 

The  rise  in  temperature  is  much  more  apparent  in  the  setting 
of  quick-setting  cements  than  in  others,  because  the  external  cool- 
ing is  relatively  much  less. 

Herzog  obtained  the  following  results  concerning  the  rise  in 
temperature  of  a  Portland  cement,  which  he  formed  while  wet  into 
a  prism  10  centimeters  long  and  at  another  time  into  a  prism  20 
centimeters  long.  In  each  case  the  original  temperature  was  13.5 
degrees  C. 


FOUNDATIONS.  335 


TEN  CENTIMETERS  LONG. 

Immediately  after  moulding 16  degrees  C. 

After  30  minutes 17  "  " 

"  70  "  17.5  «  «« 

"  4  hours 18  "  «« 

"  5  "  1 18.5  «  «« 

"  6  "  23.5  •«  " 

"  7  hours  and  30  minutes 27  "  •  «« 

"  8  "  max 29.5  "  « 

TWENTY  CENTIMETERS  LONG. 

Immediately  after  moulding 19  degrees    C. 

After  1  hour  and  30  minutes 20.5     "        «* 

"      2     "       "    30        "        22 

"     4    "      "    30        "      24 

"      5    "      "    30        "      38 

"     7    "     43        "        " 

"     8    "     45 

"     8    "    and  30  minutes,  max  45.5    "        " 

Thus  we  see  that  the  temperature  increased  16  degrees  in  one 
case  and  32  degrees  in  the  other;  accordingly  the  rise  in  tempera- 
ture was  proportional  to  the  side  of  the  cement-prism.  Thus  it 
will  be  seen  that  all  theories  about  the  rise  in  temperature  of  set- 
ting cements  have  no  value  unless  they  take  the  volume  of  cement 
into  account. 

484.  The  quantity  of  water  used  in  gauging  the  cement  has 
great  influence  upon  the  tensile  strength  and  must  be  regulated 
according  to  the  kind  of  cement,  since  every  cement  has  a  certain 
given  capacity  for  water;  of  course,  however,  in  practice  a  quantity 
that  is  somewhat  greater  than  this  must  generally  be  used. 

In  the  following  table  by  Feichtinger  it  will  be  seen  that 
the  amount  of  water  absorbed  from  the  air  by  Portland  cements 
(column  1)  and  hydraulic  limes  (columns  2,  3,  4)  varies  consider- 
ably with  the  time. 

In  practice  about  50  per  cent  of  water  is  generally  used,  which  is 
a  great  excess,  so  that  there  is  usually  about  30  per  cent  of  water  to 
be  driven  off  by  evaporation.  If  an  undue  amount  be  employed,  the 
tensile  strength  is  reduced  to  a  considerable  extent.  On  the  other 
hand,  if  the  quantity  be  as  small  as  possible  consistent  with  proper 
manipulation,  the  result  will  be  much  higher.  From  numerous 


336 


HIGHWAY   CONSTRUCTION. 


TABLE  XLIV. 
AMOUNT  OP  WATER  ABSORBED  BY  CEMENT  AND  LIME, 


1  per  cent. 

2  per  cent. 

3  per  cent. 

4  per  cent. 

Fresh  srrouiid 

99 

1  28 

61 

6  79 

After  4  hours.  ... 

1  41 

1  67 

71 

7  80 

20      "    

2  29 

2.08 

1.14 

8.26 

3  days  

5  62 

3  42 

1  82 

8  07 

7     "    

6  58 

3  85 

2  15 

11  20 

14    ««    

7.96 

4  46 

2.63 

11  80 

28     " 

10  52 

8  30 

6  20 

14  48 

80     "    

11.56 

9  50 

7  40 

14  65 

experiments  it  has  been  found  that,  as  a  general  rule,  a  proportion 
of  1  part  of  water  to  3  parts  of  cement  by  measure,  or  1  to,  3J  by 
weight,  is  the  best,  both  as  regards  convenience  of  mixing  and 
results.  With  a  much  less  quantity  the  gauging  would  be  so  stiff 
as  to  render  the  manipulation  most  difficult;  the  risk  of  air-holes, 
the  reduction  of  which  to  a  minimum  is  a  point  to  be  particularly 
attended  to,  would  be  augmented;  the  angles  of  the  mould  would 
be  imperfectly  filled,  and  generally  a  very  imperfect  briquette 
formed.  Consequently  the  results  of  such  tests  would  be  unsatis- 
factory and  unreliable.  In  general  practice  it  will  be  found  that  a 
slight  variation  in  the  above-mentioned  proportions  will  be  neces- 
sary, depending  upon  the  age  and  degree  of  fineness  of  the  cement, 
but  only  to  a  limited  extent. 

485.  Effect  of  Age   on  the   Cement.— The    age    of    Portland 
cement,  although  strictly  not  a  condition  of  manufacture,  is  an 
important  element  in  its  economical  and  safe  use.     Cement  not 
only  improves  generally  by  keeping,  but  the  older  the  cement  the 
less  danger  will  there  be  of  its  blowing,  as  the  free  lime  would  be 
acted  upon  by  the  atmosphere,  causing  it  to  slake  and  reducing  the 
danger  and  expansion  to  a   minimum.     The   age  has   also  been 
found  to  exert   considerable  influence  upon  the  rate  of  setting, 
causing  it  to  require  a  much  longer  time  to  set  than  new  cement. 

486.  Tests  of  Activity. — To  test  hydraulic  activity,  mix  cement 
with  25  to  30  per  cent  of  its  weight  of  clean  water  having  a  tem- 
perature of  between  65  and  70  degrees  Fahr.,  to  a  stiff  plastic 
mortar,  and  make  one  or  two  cakes  or  pats  two  or  three  inches  in 
diameter  and  about  |  inch  thick.     As  soon,  as  the  cakes  are  pre- 


FOUNDATIONS.  337 


pared  immerse  in  water  at  65  degrees  Fahr.,  and  note  the  time 
required  for  them  to  set  hard  enough  to  bear  respectively  a  TV- 
inch  wire  loaded  to  weigh  £  of  a  pound  and  a  ^-inch  wire  loaded 
to  weigh  1  pound.  When  the  cement  bears  the  light  weight, 
it  is  said  to  have  begun  to  set;  when  it  bears  the  heavy  weight, 
it  is  said  to  have  entirely  set.  Cements,  however,  will  increase 
in  hardness  long  after  they  can  just  bear  the  heavy  wire.  The 
activity  of  the  cement  is  measured  by  the  interval  which  elapses 
between  the  time  when  the  first  weight  is  supported  and  that  when 
the  second  is  just  borne.  Notice  that  with  the  wires  as  above  the 
weight  per  unit  of  surface  in  the  second  case  is  16  times  as  much 
as  in  the  first.  Hence  it  is  not  necessary  to  have  the  diameters  as 
stated,  but  only  to  have  the  pressure  per  unit  of  area  16  times  greater 
in  the  one  case  than  in  the  other.  The  same  wire  may  be  used  in 
both  tests,  the  load  only  being  varied.  Different  kinds  and 
brands  of  cement  vary  greatly  in  the  time  required  to  set.  Some 
brands  of  Rosendale  cement  will  support  the  heavy  wire  in  two 
minutes,  and  some  brands  of  Portland  in  not  less  than  12  hours. 
Cold. retards  the  setting.  Freshly-ground  cements  set  quicker  than 
old  ones.  The  quick-setting  cements  usually  set  so  that  experi- 
mental samples  can  be  handled  within  five  to  thirty  minutes  after 
mixing.  The  slow-setting  cements  require  from  1  to  8  hours. 

487.  Quick-  and  Slow-setting  Cements.— Cements  which  set  in 
less  than  half  an  hour  are  termed  quick-setting,  and  those  which 
do  not  set  before  two  hours,  slow-setting.     These  distinct  defini- 
tions ought  to  be  specially  introduced  in  important  specifications, 
where  they  will  prevent  misunderstandings  as  to  what  is  meant  by 
a    slow-setting    cement.     Excepting    special    cases,    slow-setting 
cements  are  more  trustworthy. 

488.  Soundness. — Soundness    refers    to    the    property   of    not 
expanding   or   contracting   or    cracking   or    checking  in   setting. 
These  effects  may  be  due  to  free  lime,  free  magnesia,  or  to  unknown 
causes.     Testing  soundness  is  therefore  determining  whether  the 
cement  contains  any  active   impurity.     An  inert  adulteration  or 
impurity  affects  only  its  economic  value,  but  an  active  impurity 
affects  also  its  strength  and  durability. 

The  most  simple  test  for  detecting  expansion  in  a  cement  is  to 
make  small  pats  with  a  trowel,  about  3  or  4  inches  square,  and 
place  them  in  water  when  sufficiently  set,  where  they  should 


338  HIGHWAY    CONSTRUCTION". 

remain  a  few  days.  If  the  cement  be  good,  they  will  show  no- 
alteration  in  form ;  but  any  cracks  showing  on  the  edges,  or  other 
deviations  from  the  original  shape  of  the  pats,  indicate  that  the- 
cement  is  of  an  expansive  nature  and  therefore  not  to  be  trusted. 
But  because  a  cement  will  not  stand  this  test  it  is  not  in  all  cases' 
to  be  condemned  as  useless,  as  its  expansive  or  blowing  property 
may  be  attributable  to  its  being  used  too  soon  after  leaving  the 
mill.  A  proper  process  of  cooling,  placing  it  in  a  thin  layer  on  a 
dry  floor  for  a  short  time,  will  correct  the  defect. 

Contraction  due  to  the  cement  being  over-clayed  may  be 
detected  by  a  similar  test  to  that  for  expansion. 

The  soundness  of  a  cement  may  also  be  tested  by  placing  some 
mortar  in  a  glass  tube  (a  swelled  lamp-chimney  is  excellent  for 
this  purpose)  and  pouring  water  on  top.  If  the  tube  breaks,  the 
cement  is  unfit  for  use  in  damp  places.  A  less  delicate  and  less 
valuable  test  than  either  of  the  above  is  to  note  whether  the 
cement  heats  when  mixed  with  water.  A  thermometer  is  some- 
times used  in  making  this  test, 

The  tests  of  soundness  should  not  only  be  carefully  conducted,, 
but  should  extend  over  considerable  time.  Occasionally  cement  is 
found  which  seems  to  meet  the  usual  tests  for  soundness,  strength, 
etc.,  and  yet  after  a  considerable  time  loses  all  coherence  and  falls 
to  pieces. 

489.  Fineness. — The  question  of  fineness  is  wholly  a  matter  of 
economy.  Cement,  until  ground,  is  a  mass  of  partially  vitrified 
clinker  which  is  not  affected  by  water  and  which  has  no  setting 
power.  It  is  only  after  it  is  ground  that  the  addition  of  water 
induces  crystallization.  Consequently  the  coarse  particles  in  a 
cement  have  no  setting  power  whatever,  and  may  for  practical 
purposes  be  considered  only  as  so  much  sand  and  essentially  an 
adulterant. 

There  is  another  reason  why  it  should.be  well  ground.  A  mor- 
tar or  concrete  being  composed  of  a  certain  quantity  of  inert  mate- 
rial bound  together  by  a  cementing  material,  it  is  evident  that  to 
secure  a  strong  mortar  or  concrete  it  is  essential  that  each  piece  of 
aggregate  shall  be  entirely  surrounded  by  the  cementing  material, 
go  that  no  two  pieces  are  in  actual  contract. 

Obviously,  then,  the  finer  a  cement  the  greater  surface  will  a. 
given  weight  cover,  and  the  more  economy  will  there  be  in  its  use. 


FOUNDATIONS.  339 


Fine  cement  can  be  produced  by  the  manufacturers  in  three 
ways:  (1)  by  supplying  the  millstones  with  comparatively  soft, 
underburnt  rock  which  is  easily  reduced  to  power;  (2)  by  running 
the  stones  more  slowly,  so  that  the  rock  remains  longer  between 
them;  or  (3)  by  bolting  through  a  sieve  and  returning  the  un- 
ground  particles  to  the  stones.  The  first  process  produces  an 
inferior  quality  of  cement,  while  the  second  and  third  add  to  the 
cost  of  manufacture. 

490.  Measuring  Fineness. — The  degree  of  fineness  of  a  cement 
is  determined   by  measuring   the  per  cent  which  will  not   pass 
through  sieves  of  a  certain  number  of  meshes  per  square  inch. 
The  committee  of  the  American  Society  of  Civil  Engineers  recom- 
mended the  determination  "by  weight  of  the  per  cent  that  is 
rejected  by  sieves  of  2500,  5476,  and  10,000  meshes  to  the  square 
inch  respectively,  the  first-mentioned  sieve  being  of  No.  35,  the 
second  of   No.  37,  and  the  third  of   No.  40,  wire  gauge.     These 
sieves  are  usually  referred  to  by  the  number  of  meshes  per  linear 
inch;  the  first  being  known  as  No.  50,  the  last  as  No.  100.     It  is 
stated  that,  as  sold,  the  number  of   meshes  varies  somewhat,  and 
the  number  of  wires  is  generally  less  by  about  10  ten  per  cent 
than  the  number  of  the  sieve.     The  diameter  of  the  holes  is  about 
equal  to  the  diameter  of  the  wire. 

German  Portland  cements  are  commonly  ground  finer  than 
English.  "  Most  English  manufacturers  grind  their  cement  to 
such  a  degree  of  fineness  that  when  sifted  through  a  sieve  having 
2500  holes  (50  by  50)  to  the  square  inch,  it  shall  leave  a  residue  of 
not  more  than  10  per  cent  by  weight.  Cement  ground  to  this 
fineness  will  leave  from  19  to  20  per  cent  of  residue  cm  a  4900 
(70  by  70)  sieve,  and  practically  nothing  on  a  625  (25  by  25)  sieve." 
This  is  supposed  to  be  the  most  economical  degree  of  fineness. 

Different  brands  of  Kosendale  cement  vary  considerably  in  their 
fineness.  Those  of  the  best  reputation  will  leave  from  4  to  10  per 
cent  residuum  on  the  No.  50  sieve;  other  brands,  from  10  to  23  per 
cent. 

491.  Strength.— Although   in  ordinary  practice   cements   are 
subject  only  to  compression,  yet  at  the  present  time  all  tests  are 
made  with  a  view  to  ascertaining  their  tensile  strength.     The  rea- 
son for  this  is  that  comparatively  light  strains  produce  rupture; 
and  that  when  rupture  does  take  place,  the  strain  causing  it  is  really 


340  HIGHWAY   CONSTRUCTION. 


due  to  tension  produced  by  the  sinking  of  one  part  of  the  structure 
and  not  to  compressive  force. 

492.  The  Testing-machine. — The  details  of  the  form  of  the 
specimen  to  be  tested  (the  briquette),  as  recommended  by  the  Com- 
mittee of  the  American  Society  of  Civil  Engineers,  are  given  in  Fig. 
33.  The  method  of  placing  the  briquette  in  the  machine  is  shown 
in  Fig.  34.  In  applying  the  stress,  it  is  also  recommended  to  make 
the  initial  strain  0,  and  increase  it  regularly  at  the  rate  of  400 
pounds  per  minute  until  rupture  takes  place.  "  For  a  weak  mix- 
ture one  half  the  speed  is  recommended." 

There  are  many  machines  on  the  market,  made  specially  for 
testing  the  strength  of  cement.  Fig.  35  represents  a  cement-test- 
ing machine  which  can  be  made  by  an  ordinary  mechanic  at  an 
expense  of  only  a  few  dollars.  Although  it  does  not  have  the  con- 
veniences and  is  not  as  accurate  as  the  more  elaborate  machines,  it 
is  valuable  where  the  quantity  of  work  will  not  warrant  a  more 
expensive  one,  and  in  many  cases  is  amply  sufficient. 

It  was  devised  by  F.  W.  Bruce  for  use  at  Fort  Marion,  St. 
Agustine,  Florida,  and  reported  to  the  Engineering  News  by  Lieu- 
tenant W.  M.  Black,  U.  S.  A. 

The  machine  consists  essentially  of  a  counterpoised  wooden 
lever  10  feet  long,  working  on  a  horizontal  pin  between  two  broad 
uprights  20  inches  from  one  end.  Along  the  top  of  the  long  arm 
runs  a  grooved  wheel  carrying  a  weight.  The  distances  from  the 
fulcrum  in  feet  and  inches  are  marked  on  the  surface  of  the  lever. 
The  clamp  for  holding  the  briquette  for  tensile  tests  is  suspended 
from  the  short  arm,  18  inches  from  the-  fulcrum.  Pressure  for 
shearing  and  compressive  stresses  is  communicated  through  a  loose 
upright,  set  under  the  long  arm  at  any  desired  distance  (generally 
6  or  12  inches)  from  the  fulcrum.  The  lower  clip  for  tensile 
strains  is  fastened  to  the  bed-plate.  On  this  plate  the  cube  to  be 
crushed  rests  between  blocks  of  wood,  and  to  it  is  fastened  an  up- 
right with  a  square  mortise  at  the  proper  height  for  blocks  to  be 
sheared.  The  rail  on  which  the  wheel  runs  is  a  piece  of  light 
T  iron  fastened  on  top  of  the  lever.  The  pin  is  iron,  and  the  pin- 
holes  are  reinforced  by  iron  washers.  The  clamps  are  wood,  and 
are  fastened  by  clevis  joints  to  the  lever-arm  and  bed-plate  respec- 
tively. When  great  stresses  are  desired,  extra  weights  are  hung  on 


FOUNDATIONS. 


341 


Pig.  33.  FORM  OF  BRIQUETTE.-, 


O3 


SECTION.AS 


Pig.34. 


Pig-.35. 


342  HIGHWAY   CONSTRUCTION. 

the  end  of  the  long  arm.     Pressures  of   3000  pounds  have  been 
developed  with  this  machine. 

493.  Most  of  the  tests  made  in  this  country  and  England  are 
carried  out  for  the  purpose  of  ascertaining  the  strength  of  neat 
cements,  although  such  material  is  rarely,  if  ever,  used  without  the 
admixture  of  sand.    In  Europe,  on  the  other  hand,  the  practice  was 
established  about  ten  years  ago,  both  by  manufacturers  and  engi- 
neers, to  determine  the  value  of  a  cement  by  testing  it  when  mixed 
with  sand  into  mortar,  the  usual  proportions  of  the  mixture  being 
three  volumes  of  sand  to  one  volume  of  cement.     It  is  obvious  that 
the  latter  practice  is  preferable,  since  thereby  a  knowledge  of  the 
strength  and  properties  of  the  binding  material  actually  used  in 
the  work  will  be  gained,  and  furthermore  because  no  valid  infer- 
ence as  to  the  cohesion  of  a  mortar  can  be  drawn  from  a  statement 
of  the  tensile  strength  of  the  neat  cement. 

Tests  of  this  kind  should,  therefore,  be  made  with  cement 
mortar  mixed  in  the  same  proportions  as  contemplated  in  the  work 
itself,  and  also  with  the  same  sand  if  practicable,  inasmuch  as  the 
quality  of  the  latter  exerts  a  marked  influence  upon  the  resulting 
strength  of  the  mortar.  In  general,  it  may  be  said  that  the  greater 
the  proportion  of  sand  in  the  mortar  tested  the  more  accurately 
can  the  actual  cementing  quality  of  the  cement  be  indicated. 

494.  Cement-mortar  is  composed  of  hydraulic  cement  and  sand 
in  varying  proportions,  depending  upon  the  kind  and  quality  of  the 
cement.     Cement-mortar  differs  from  lime-mortar  in  its  setting,  in 
that  it  sets  within  itself  without  the  aid  of  external  elements.    More- 
over, cement  forms  by  the  addition  of  water  a  chemical  combination 
throughout   all   its  parts,  and  setting   or   hardening   takes  place 
throughout  the  whole  mass  almost  simultaneously.     The  strength 
of  cement  over  lime  mortar  is  shown  by  tests  at  the  Watervliet 
(N.  Y.)  Arsenal  to  be  about  two  to  one  in  favor  of  the  former. 

495.  Quality  of  Mortar. — Good  mortar  should  have  plasticity 
when  mixed  with  large  quantities  of  sand,  and  after  solidification 
compressive  strength  and  tensile  strength,  as  evidence  of  inde- 
pendent cohesion,  power  to  resist  the  action  of  frost  and  heat,  and 
adhesive  qualities  for  cementing  blocks  into  monolithic  bodies.     It 
is  to  be  invariable  in  volume  during  and  after  solidification,  to  be 
weather-proof  and,  for  hydraulic  works,  also  water-tight. 

496.  Quality  of   Sand. — The  sand   imparts  crushing  strength, 


FOUNDATIONS.  343 


lessens  shrinkage,  and  saves  expense  in  lime-mortars.  Hydraulic 
cements  require  sand  only  at  exposed  surfaces.  Otherwise  it  serves 
as  an  adulterant  for  reducing  a  surplus  of  strength  and  density 
to  actual  requirements  of  a  given  bulk.  The  sand  should  be 
clean,  sharp,  large-grained,  not  too  uniform  in  size,  free  from  loam, 
vegetable  or  clayey  substances,  well  screened,  and,  if  accessary, 
washed.  Admixed  particles  of  clay  adhere  to  the  sand  and  form 
diaphrams  between  sand  and  mortar,  which  for  durable  harden- 
ing require  close  contact. 

Since  sand  is  mostly  used  in  greater  quantities  than  the  cement- 
ing substances,  it  equals  them  in  importance.  It  is  in  all  classes 
embedded  in  the  matrix  as  a  mechanical  mixture.  The  tensile  and 
crushing  strengths  of  the  same  cement,  with  equal  quantities  of 
different  qualities  of  sand,  vary  more  than  those  of  different  brands 
of  cement  within  the  same  group  do  among  themselves. 

497.  Quality  of  Water. — Fresh  or  salt  water  may  be  used  in 
mixing  the  mortar,  provided  it  is  clean;  but  salt  water  may,  with 
some  natural  cements,  hinder  the  setting. 

498.  Quantity  of  Water. — In  regard  to  the  proper  amount  of 
water  to  be  used  in  tempering  a  cement-mortar,  it  may  be  said 
that  this  will  depend  upon  the  quality  and  quantity  of  sand,  as  also 
upon  the  quality  of  the  cement.     From  the  numerous  and  careful 
experiments  with  Portland  and  Rosendale  cements,  made  a  few 
years  ago  by  Mr.  Eliot  C.  Clarke,  C.E.,  and  published  in  the  Trans- 
actions of  the  American  Society  of  Civil  Engineers  for  April,  1885, 
the  inference  was  drawn  that,  "  as  a  rule,  American  cements  re- 
quire more  water  than  Portland,  fine-ground  more  than  coarse,  and 
quick-setting  more  than  slow-setting  cements/'     For  experimental 
purposes  in   the  laboratory,  the    amount   of  water  added  by   Mr. 
Clarke  to  the  dry  mixture  of  sand  and  cement  was  usually  about 
one  fourth  of  the  weight  of  the  Portland  and  one  third  of  the 
weight  of  the  American  cement  contained  in  the  batch;  but  these 
amounts  were  increased  or  diminished  somewhat  in  order  to  obtain 
mortars  of  uniform  consistency.     Mr.  Clarke  adds,  in  mixing  mor- 
tars on   the   site  of  public  works,  and   particularly  for  concrete 
works,  much  larger  quantities  of  water  than  are  used  by  him  for 
testing  purposes   are  commonly  added  by  workmen  in  order  to 
render  the  labor  of  mixing  and  spreading  less  difficult,  but  that  the 
result  of  this  procedure  is  always  a  greater  or  less  loss  of  strength. 


344  HIGHWAY    CONSTRUCTION. 

For  the  standard  tests  of  cement-mortars  by  European  engineers 
the  rules  prescribe  one  part  by  weight  of  cement,  three  parts  by 
weight  of  normal  sand,  and  four  tenths  of  a  part  by  weight  of 
clean  fresh  water. 

499.  Strength  of  Mortar. — Three  classes  of  strength  are  re- 
quired in  all  mortars,  viz.,  adhesive,  compressive,  and   shearing. 
These  strengths  are  all  dependent  upon  the  strength  of  the  cement, 
the  strength  of  the  sand,  and  upon  the  adhesion  of  the  former  to 
the  latter. 

500.  Adhesive  Strength. — It  is  commonly  assumed  that  after 
the  lapse  of  a  moderate  time  the  adhesive  and  cohesive  strengths 
of  cement-mortars  are  about  equal,  and  that  in  old  work  the  former 
exceeds  the  latter.     Modern  experiments,  however,  fail  to  establish 
the  truth  of  this  assumption,  and  indicate  rather  that  the  adhesion 
of  such  mortars  to  bricks  or  stones  is  much  less  than  the  tensile 
strength  during  the  first  few  months;  also  that  the  relation  be- 
tween the  adhesive  and  cohesive  strengths  of  both  neat  cements 
and  mixtures  with  sand  are  very  obscure.     It  has  been  found  that 
the  adhesion  of  mortars  to  bricks  or  stone  varies  greatly  among  the 
different  kinds  of  these  materials,  and  particularly  with  their  po- 
rosity; it  also  varies  with  the  quality  of  the  cement,  the  character, 
grain,  and  quantity  of  sand,  the  amount  of  water  used  in  tempering, 
the  amount  of  moisture  in  the  stone  or  brick,  and  the  age  of  mor- 
tar.    Some  cements  which  exhibit  high  tensile  strength  give  low 
values  for  adhesion,  and  conversely  cements  which  are  apparently 
poor  when  tested  for  cohesion  show  excellent  adhesive  qualities. 
Quick-setting  cements  are  usually  found  to  give  greater  adhesive 
strength  than  slow-setting  ones,  while  in  the  case  of  cohesion  the 
opposite  is  generally  true.     Under  these  circumstances,  therefore, 
it  is  manifest  that  a  test,  at  various  stages  of  age,  of  the  adhesive 
properties  of  a  binding  material  like  cement-mortar  should  be  re- 
garded as  a  very  important  one,  in  the  case  of  masonry  structures 
which  must  soon  after  completion  be  subjected  to  other  than  com- 
pressive strains,  and  it  is   to  be  regretted  that  so  comparatively 
little  information  respecting  such  tests  with  cements  and  mortars 
as  made  at  the  present  time  is  available. 

To  assist  somewhat  in  arriving  at  a  fair  measure  of  the  strength 
of  hydraulic  mortars  at  different  periods  of  time,  as  well  as  the 
proper  composition  of  the  same,  the  statistics  given  in  Table  XLV 
have  been  compiled  from  a  great  variety  of  sources: 


FOUNDATIONS. 


345 


TABLE  XLV. 
ADHESIVE  STRENGTH  OF  MORTARS. 


1 

* 

!i 
I 

Kind  of  Cement  Used. 

Materials 
cemented  to- 
gether. 

Average  Adhesive 
Strength  in  Ib's. 
per  sq.  in. 

Authority. 

-  a 

53    D 

M 

Cement,  1. 
Sand,  1. 

Cement,  1. 
Sand,  2. 

Cement,  1. 
Sand,  3. 

1  Cement,  1. 
Sand.  4. 

7 

7 
7 
? 
7 
7 
7 
7 
16 
16 
28 
28 
28 
30 
30 
30 
30 
30 
30 
30 
30 
30 
30 
30 
30 
30 
42 
48 
56 
90 
95 
110 
180 
180 
180 
180 
180 
180 

270 
320 
lyr. 

" 

Quick-setting  cement 
Portland 

Hydraulic  lime 
Portland 

Quicklime 
Lime  and  cement 
Hydraulic  lime 
Portland 

Quick-setting  cement 
Slow-        " 
Rosendale 

Portland 

Blue  lias  lime 

Lime  and  pozzuolana 
Portland 

Hydraulic  lime 
Portland 
Hydraulic  lime 
Quicklime 

Portland 

Lime  and  pozzuolana 
Rosendale 
Quicklime 
Good  quicklime 
Ordinary  hydraulic  lime 
Good     ' 

Portland 
it 

Hard  brick 

Sawed  limestone 
Cut  granite 
Polished  marble 
Bridgewater  brick 
Brick  t 

Limestone 
Brick  t 

!!   * 

Hard  brick 

Croton  brick 
Fine  cut  granite 
Sawed  limestone 
Cut  granite 
Polished  marble 
Bridgewater  brick 
Sandstone 
Staffordshire  brick 
Gray  stock  brick 
Common  soft  brick 
Hard  brick 
Brick  H 
"      If 
"      H 
"      t 

::  j! 

Limestone 
Hard  brick 
Soft 
Sawed  slate 
Portland  stone 
Polished  marble 
Hard  brick 
Croton  brick 
Not  stated 

«        <t 

Materials  in  air 
"         "  water 
Gault    clay   brick 
pressed 
Stock  brick  in  air 
"         "in  water 
Staffordshire    blue 
brick  in  air 
Staffordshire    blue 
brick  in  water 
Fareham  red  brick 
in  air 
Fareham  red  brick 
in  water 

*98 

Robertson,  1858 
I.  J.  Mann,  1883 

Dr.  Bohme,  1883 
Prof.  Warren,  '87 

Boistard 

Dr.  Bohme,  1883 
Prof.  Warren,  '87 

Rober  son,  1858 
Gen.  Gillmore,  '63 

'57 

41 
38 
19 
24.1 
168 

35!  i 

213 

.... 

*15 

.... 

"21 
102 
117 

30  '.4 
105 
146 

is!? 

38 
53 
9-15 
5 
25.5 
45 
73 
*59 
*30 
12.3 
12.0 

15.3 
20 
26 

26!9 
24 

48 

8.8 
9.2 

13.2 
9 
16 

i?!5 
14 
45 

'.5!2 

30.8 
27.5 

78 
i|97 
1(71 
1166 
49 

15.7 
20.8 

Lc  J.  Mann,  1882 

U                     li                it 

Building  News,'80 

J.  White,  1832 
Bauschinger,  1873 

Dr.  Bohme,  1883 
Bauschinger,  1873 

Rondolet,  1831 
Robertson,  1858 
I.  J.  Mann,  1883 

J.  White,  1832 
Gen.  Gillmore,  '63 
Vicat,  1818 

ti         ti 
Mallet,  1829 

J.  Grant,  1871 
u        it         i< 
t       ti        it 
it       ti        <« 
ii       it         (i 

t!                 11                   II 

'••• 

*40 
*36 
*18 
**i 

68.8 

46.9 

04  9 

39!3 

54 
41.9 

56.9 
38.9 

*33 

28.1 
14.2 
12.8 

22.6 

*15 

'(62 
1155 
1175 

*40 
*18 

.... 

"*8 

68 

40 

24 

*•?} 

"*85 
*140 

*51 

70 

45 
78 
96 

48 
40 
126 
123 

99 

44 
63 
70 

47 
29 
S3 
62 

.... 

*  Proportions  of  sand  not  given,  but  presumably  about  those  indicated  in  headings  of  table. 
t  Standard  sand  used  in  mixture.                     t  Clean  river  sand  used  in  mixture. 
§  Crushed  sandstone  used  in  mixture.             f  Fine  river  sand  used  m  mixture. 
1  Coarse  particles  in  cement  sifted  out  before  testing. 

346 


HIGHWAY    CONSTRUCTION. 


501.  Shearing  Strength. — In  recent  times  elaborate  experiments 
to  ascertain  the  shearing  strength  of  mortar,  both  in  the  joints  of 
brickwork  and  separate  blocks,  have  been  made  by  Prof.  Bausch- 
inger of  Munich.  The  results  are  too  numerous  for  a  verbal 
description,  and  they  are  accordingly  given  in  Table  XLVI.  None 
of  the  values  obtained  are  very  large,  ranging  after  ninety  days 
from  70  to  7  pounds  per  square  inch  on  brickwork  with  mortar 
mixed  in  the  proportion  of  three  parts  of  relatively  fine  river  sand 
to  one  of  cement-lime.  The  shearing  strength  of  cubes  of  mortar 
also  appears  to  be  considerably  greater  than  that  of  the  compara- 
tively thin  joints  in  brickwork,  and  to  be  influenced  by  the  quality 
of  the  sand. 


TABLE  XLVI. 
SHEARING  STRENGTH  OF  CEMENTS  AND  MORTARS. 


Age  in  Days  when 
Tested. 

Kind  of  Cement. 

Average  Shearing  Strength 
in  Ibs.  per  sq.  in. 

Authority. 

Neat 
Cement. 

. 

a_r 
£  c 

6* 

Cement, 
Sand,  2. 

Cement, 
Sand,  3 

Cement, 
Sand,  4. 

3* 

Sf 

Q& 

42 
49 
52 
90 
90 
90 

50 
60 
1  w'k 

Sw'ks 
4w1ks 
Sw'ks 

I. 

Shear  in,  and  parallel 
to,  bed-joints  of  brick- 
tvork. 

Portland  (Bonn)*  
"              "     *   .... 
"              "     *'.'.  ... 
"          (Perlmoosj*. 
Hydraulic  lime* 

73.'9 

iss 

72.5 

m.6 

*64' 

'22!  7 
76.8 
7.1 

142.2 
362.6 
108  1 

Prof.  Bauschinger,  1873 

u 

M 
M 

Prof.  Bauschinger,  1873 

1878 

.... 



Quicklime* 

320  0 

'66*.  8 
78.2 
93.9 
122.3 
112.3 
137.9 
167.8 
199.1 

II. 

Shear  in  cubes  of  ce- 
ments and  mortars 
dried  in  air. 

Portland  (Bonn)*  
"          (Perlmoos)t. 

t                ;;      §. 

1         S: 

%                  §. 

1!                                   §• 

369.7 
256.0 
224.7 
301.5 
270.2 
322.8 
257.4 
341.3 
258.8 
376.8 

369.7 
405.3 

284.4 
383.9 

!  :! 

.... 

123.7 
128.0 
163.5 
153.6 
199.1 
196.2 
237.5 

*  Fine  river  sand.  t  Coarse  sand. 

t  Average  values  for  series  of  four  different  brands  of  quick-setting  cements. 

§  Clean,  medium  sand. 

I  Average  values  for  series  of  four  different  brands  of  slow-setting  cements. 


FOUNDATIONS. 


34' 


As  in  tlie  case  of  adhesion,  no  exact  relation  between  the  tensile 
the  shearing  strengths  of  mortar  placed  in  brickwork  can  yet 
be  deduced,  owing  to  the  lack  of  sufficient  data;  but,  on  the  other 
hand,  the  experiments  show  that  the  shearing  strength  of  blocks  or 
oubes  of  mortar  is  about  20  per  cent  greater  than  the  tensile  strength 
under  the  same  circumstances. 

502.  Compressive  Strength.— But  few  experiments  have  been 
made  upon  the  compressive  strength  of  mortar.     An  examination 
of  the  results  of  about  sixty  experiments  made  with  the  Watertown 
testing-machine  seems  to  show  that  the  compressive  strength  of 
mortar,  as  determined  by  testing-cubes,  is  from  8  to  10  times  the 
tensile  strength  of  the  same  mortar  at  the  same  age.     Data  deter- 
mined by  submitting  cubes  of  mortar  to  a  compressive  strain  are  of 
little  or  no  value  as  showing  the  strength  of  mortar  when  employed 
in  thin  layers,  as  in  the  joints  of  masonry.     The  strength  per  unit 
of  bed  area  increases  rapidly  as  the  thickness  of  the  test-specimen 
•decreases,  but  no  experiments  have  ever  been  made  to  determine 
the  law  of  this  increase  for  mortar. 

503.  Tensile  Strength. — The  following  table,  carefully  compiled 
from  a  large  number  of  reliable  experiments,  gives  the  tensile 
strength  of  cement-mortar : 

TABLE  XLVII. 

TENSILE  STRENGTH  OP  CEMENT-MORTAR. 


Composi>ion 


Age  of  Mortar. 


Mortar. 

Rosendale. 

Portland. 

Cement 

Sand. 

1  Week. 

1  Month. 

6  Months 

1  Year. 

1  Week. 

1  Month. 

6  Months 

1  Year. 

1 

0 

100 

180 

275 

300 

300 

400- 

450 

500 

1 

1 

60 

100 

180 

225 

175 

250 

340 

375 

1 

2 

25 

60 

125 

170 

120 

150 

245 

290 

1 

3 

20 

40 

80 

120 

90 

110 

175 

220 

1 

4 

15 

25 

60 

90 

75 

'75 

130 

170 

1 

5 

10 

15 

50 

80 

60 

65 

110 

130 

1 

6 

6 

10 

45 

75 

50 

35 

90 

100 

504.  Fineness  of  Sand.— Vicat,  in  the  course  of  elaborate  ex- 
periments with  limes  and  mortars  in  the  early  part  of  this  century, 


348  HIGHWAY   CONSTRUCTION. 

established  standards  for  size  of  grain  of  what  he  termed  coarse 
sand  and  fine  sand,  as  follows ;  coarse  sand  being  such  as  will  pass 
through  a  sieve  of  64  meshes  per  square  inch  and  be  retained  on 
one  of  289  meshes  per  square  inch,  while  fine  sand  will  pass  through 
a  sieve  of  289  meshes  per  square  inch  and  be  retained  on  one  of  625 
meshes  per  square  inch.  On  this  definition  he  ranked  the  superi- 
ority of  coarse,  mixed,  and  fine  sands  with  limes  according  to  the 
following  schedule : 

For  eminently  hydraulic  limes,  1,  fine;  2,  mixed;  3,  coarse. 

For  slightly  hydraulic  limes,  1,  mixed;  2,  fine;  3,  coarse. 

For  fat  or  quick  limes,  1,  coarse;  2,  mixed;  3,  fine. 

It  will  suffice  to  say  that  with  cement-mortars  much  better 
results  are  obtained  when  the  sand  is  of  the  size  of  grain  above 
described  and  is  sharp  and  clean. 

Mr.  Clarke  says  that  when  the  sand  was  formed  of  a  mixture  of 
fine  and  coarse  grains  nearly  as  good  results  were  attained  as  with 
coarse  grains  alone. 

Before  leaving  this  subject  it  may  be  of  interest  to  refer  briefly 
to  the  experiments  made  at  Wilhelmshaven  in  1877  by  H.  Arnold,. 
C.E.,  as  published  in  the  Journal  of  the  Hanoverian  Architects 
and  Engineers'  Society  for  1883,  and  from  which  was  found  that 
the  size  of  grain  and  quality  of  the  sand  used  in  Portland -cement 
mortar  are  important  factors  in  its  ultimate  strength.  With  six 
different  kinds  of  substantially  clean  sands  and  the  same  brand  of 
cement  mixed  into  mortar  in  the  proportions  of  three  volumes  of 
sand  to  one  volume  of  cement,  the  tensile  strength  after  seven  days 
ranged  from  101  to  243  pounds  per  square  inch,  and  after  twenty- 
eight  days  from  133  to  311  pounds  per  square  inch,  thus  exhibiting 
extrdniely  wide  variations,  depending  largely  upon  the  size  and 
roughness  of  the  grains  of  sand. 

In  every  instance  it  was  found  that  a  greater  strength  was  de- 
veloped with  a  coarse-grained  sand  free  from  very  fine  particles 
and  dust  than  with  a  fine-grained  sand,  both  being  equally  sharp. 
Mr.  Arnold  also  points  to  the  fact  deduced  from  his  experiments, 
that  with  the  same  cement  but  different  sands  of  similar  size  of 
grain,  the  cohesion  of  the  mortar  may  be  found  to  vary  consider- 
ably, and  will  probably  depend  upon  the  chemical  composition  of 
the  sand.  He  therefore  concludes  that  in  order  to  obtain  satis- 
factory results  from  the  cement-mortar  used  in  the  construction  of 


FOUNDATIONS.  349 


public  works,  the  quality  of  the  sand  available  in  the  particular 
locality  should  first  be  taken  into  careful  consideration. 

If  no  other  than  a  fine  sand  happens  to  be  available  and  a  given 
strength  of  the  mortar  is  to  be  attained  at  the  end  of  one  week, 
experiments  should  be  made  to  earn  whether  the  proportions  of 
sand  to  cement  named  in  the  specifications  should  be  changed, 
since  the  strength  diminishes  rapidly  with  the  quantity  of  sand 
used;  and  in  such  an  event  it  may  also  be  advisable  to  use  an 
entirely  different  kind  of  cement.  It  is  a  necessary  condition  of 
success  in  mortar-making  that  every  particle  of  the  sand  or  "  aggre- 
gate "  be  completely  covered  with  the  cement  or  "  matrix  •"  and 
since,  when  the  grains  in  a  given  volume  are  small,  the  magnitude 
of  the  total  surface  to  be  covered  is  greater  than  when  the  grains 
are  large,  it  follows  that  fine  sand  requires  a  larger  proportion  of 
cement  than  coarse  sand.  Any  specification  or  plan  contemplating 
the  use  of  a  good  coarse  sand  must,  therefore,  be  altered  if  fine 
sand  alone  is  used,  or  else  the  quality  of  the  work  will  be  im- 
paired. 

In  support  of  the  foregoing  remarks,  it  has  been  quite  generally 
observed  by  engineers  that  when  most  of  our  American  natural 
cements  are  mixed  entirely  with  fine  sand  the  process  of  hardening 
is  greatly  retarded,  even  if  not  entirely  prevented;  while  the  same 
cements,  when  tested  neat,  exhibit  a  cohesive  strength  ranging 
from  50  to  136  pounds  in  twenty-four  hours,  thus  showing  conclu- 
sively the  effect  of  admixing  the  fine  material.  An  instructive  in- 
stance of  this  kind  was  noticed  some  years  ago,  when  an  excellent 
quality  of  Akron  "Star"  cement  was  mixed  with  very  fine  sand 
from  the  Pinnacle  pits  in  the  proportion  of  2 1  parts  sand  to  1  part 
of  cement.  For  several  days  the  mass  remained  in  a  plastic  state 
in  the  tin  can  in  which  it  had  been  deposited,  and  upon  being 
/emoved  and  exposed  to  the  air  upon  a  window-sill  for  several 
months  it  displayed  very  little  strength  and  broke  in  handling. 
On  the  approach  of  cold  weather  the  largest  fragment  was  kept  in 
an  apartment  constantly  heated  by  steam,  and  after  lying  undis- 
turbed therein  for  three  months  pieces  could  easily  be  broken  off 
with  the  fingers.  At  the  present  time,  after  having  attained  an 
age  of  one  year,  it  is  still  quite  friable  and  entirely  unfit  for  use. 
Another  mass  of  mort-ar  prepared  at  the  same  time  from  the 
same  cement,  but  with  clean,  coarse  sand,  mixed  in  the  proportions 


350 


HIGHWAY   CONSTRUCTION. 


of  3  parts  of  sand  to  1  part  of  cement,  indurated  promptly  and 
exhibited  far  better  qualities. 

TABLE  XLVIII. 

EFFECT  OF  SIZE  OF  GRAIN  OF  SAND  ON  TENSILE  STRENGTH  off 
CEMENT-MORTAR. 


Denomination  of  Size  of  Grains. 

Dangast  Sand 
after 

Crushed  Granite 
after 

7  days. 

28  days. 

7  days. 

28  days. 

Hulled  barley  

177 
162 
131 
134 
141 

64 

213 
191 

177 
164 
160 

87 

194 
176 
164 
144 
136 

87 

255 
234 
242- 
192 
193 

134 

Oatmeal     .     .    .  .....   

Grit  

Coarse  dust       ) 

Fine  dust  ) 

Tensile  Strength  of  Mortar  mixed  3  :  1 
with 


TABLE  XLIX. 
CHARACTER  OF  SIEVES  FOR  SIFTING  SANDS. 


Number  of  Sieve. 

Number  of 
Holes  per 
lineal  inch. 

Number  of 
Holes  pei- 
square  inch. 

Size  of  Hole  of 
Length  of  Side 
in  inches. 

Diameter  of 
Wire  in  inches. 

1  

20 

400 

.03101 

.01899 

2  

30 

900 

.02119 

.01214 

3  

50 

2500 

.01119 

.00881 

4  

80 

6400 

.00599 

.00510 

5  

170 

28900 

.00309 

.  00279 

505.  Portland  cement  acquires  its  strength  more  quickly  than 
Rosendale.  Both  cements,  but  especially  the  Rosendale,  harden 
more  and  more  slowly  as  the  proportion  of  sand  mixed  with  them 
increases ;  and  whereas  neat  cement  and  rich  mortars  attain  nearly 
their  ultimate  strength  in  six  months  or  less,  weak  mortars  con- 
tinue to  harden  for  a  year  or  more.  It  has  also  been  found  that 
after  a  period  of  about  a  year  weak  mortars  often  lose  in  strength 
or  tenacity  what  they  may  gain  in  hardness,  from  the  fact  of  their 


FOUNDATIONS.  351 


becoming  brittle.  Specimens  of  such  mortar  two  years  old  break 
very  irregularly.  Mortars  less  than  one  month  old  are  relatively 
weak,  and  hence  the  advantage  of  waiting  as  long  as  possible  before 
loading  masonry  structures.  Portland-cement  mortars  are  especially 
useful  in  cases  where  the  structure  is  necessarily  subjected  to  severe 
strains  within  so  short  a  period  as  one  week,  as  frequently  happens 
in  the  case  of  pavements. 

506.  Permeability  of  Mortar.— The  permeability  of  mortar  is 
increased  as  the  proportion  of  the  cement  decreases.     It  increases 
with  the  coarseness  of  the  sand.     Mortars  made  with  a  mixture  of 
sand  of  various  sizes  are  relatively  non-porous  and  non-permeable. 
Mortars  mixed  dry  are  more  permeable  than  those  mixed  wet  or  of 
a  "  normal  consistency." 

507.  Effect  of  Frost  upon  Mortars. — It  is  a  matter  of  common 
knowledge  that  ordinary  quick-lime  mortar  which  is  exposed  to  the 
action  of  frost  before  it  has  become  well  set  or  indurated  will  thereby 
become  greatly  injured  in  its  adhesive  and  cohesive  properties ;  and 
hence  where  such  mortar  is  used  it  is  customary  to  suspend  all  build- 
ing operations  on  the  arrival  of  the  cold  season.     Should,  however, 
it  be  necessary  to  proceed  with  the  construction,  experienced  masons 
and  builders  sometimes  make  use  of  a  quick-setting  cement-mortar 
in  place  of  lime,  and  cease  work  when  the  weather  is  at  all  severe. 
It  is,  therefore,  of  importance  to  learn  something  of  the  behavior 
of  cements  under  such  circumstances. 

The  impression  seems  to  prevail  quite  extensively  that  cement- 
mortars  are  riot  appreciably  injured  by  freezing,  and  that  masonry 
may  safely  be  constructed  at  any  temperature  below  the  freezing 
point  at  which  a  man  can  still  work,  provided  that  either  brine  or 
salt  be  used  instead  of  fresh  water,  or  that  the  materials  be  first 
heated.  With  regard  to  the  use  of  brine  or  salt  it  may  be  remarked 
that  whether  the  mortar  will  be  injured  thereby  or  not  seems  to 
depend  principally  upon  the  character  of  the  cement.  Most  of  the 
natural  or  "  Roman"  cements  suffer  a  considerable  loss  of  strength 
if  mixed  with  salt  water,  while  the  Portland  cements  do  not  appear 
to  be  materially  affected. 

Respecting  the  practice  of  heating  the  cement,  sand,  and  water 
before  mixing,  and  then  using  the  hot  mortar  in  cold  weather  upon 
frosty  stones  or  bricks,  or  depositing  it  in  icy  water,  the  experiments 
of  William  W.  Maclay,  C.E.,  submitted  in  1877  to  the  American 


352  HIGHWAY   CONSTRUCTION. 


Society  of  Civil  Engineers,  show  indisputably  that  such  a  method 
of  treatment  is  erroneous,  and  that  a  great  amount  of  injury  is 
effected  when  heated  mortar,  even  if  made  of  Portland  cement,  is 
immersed  directly  in  cold  water.  The  tests  were  all  made  with 
Burham  Portland  cement,  which,  when  tested  neat  at  ordinary 
temperature,  gave  a  tensile  strength  of  278  pounds  per  square  inch 
after  seven  days.  In  one  series  of  experiments  the  ingredients  of 
the  mortar  all  had  a  temperature  of  about  40  degrees  Fahr.,  and  in 
another  they  were  heated  to  100  degrees  Fahr.  These  two  sets  of 
briquettes  were  kept  for  seven  days  in  precisely  the  same  manner, 
and  were  broken  on  the  same  day,  so  that  any  changes  in  tempera- 
ture during  this  period  would  necessarily  affect  them  alike.  The 
averages  of  the  tensile  strengths  acquired  show  that  by  first  heating 
the  ingredients  to  about  100  degrees,  then  mixing  them  in  air 
having  a  temperature  of  from  13  to  37  degrees,  and  afterward 
exposing  the  briquettes  for  six  days  to  the  winter  weather,  their 
strength  in  the  case  of  neat  cement  was  only  from  7  to  20  per  cent 
of  that  attained  when  the  materials  were  mixed  without  heating,  or 
with  the  temperature  of  the  mortar  at  40  degrees;  and  in  the  case  of 
mortar  mixed  in  the  proportion  of  2  sand  to  1  cement,  the  tensile 
strength  of  the  heated  mortar  after  28  days  was  only  30  per  cent  -of 
that  reached  by  the  cold  mortar  at  40  degrees.  From  these  and 
other  similar  experiments  Mr.  Maclay  concludes  that  the  mixing 
of  cement-mortar  with  highly-heated  materials  for  use  above  water 
in  very  low  temperatures  greatly  reduces  its  normal  strength,  and 
that  for  use  below  icy  water  its  value  will  thereby  be  almost  entirely 
destroyed.  If  mortar  must  be  used  at  all  in  such  weather,  it  should 
be  used  cold,  and  the  only  condition  to  be  observed  is  that  the 
materials  shall  be  free  from  frost  at  the  time  of  using.  "  In  the 
experiments  where  the  materials  were  mixed  cold  and  then  exposed 
to  the  winter  weather,  Portland-cement  mortar  appeared  to  set 
without  freezing  even  in  as  low  a  temperature  as  13  degrees  Fahr., 
except  when  it  was  windy;  but  where  the  briquettes  were  made  of 
hot  mortar  they  invariably  froze,  as  was  proven  by  their  becoming 
soft  again  when  the  temperature  rose." 

Portland  cement  was  found  to  possess  the  peculiarity,  also 
noticed  by  many  other  writers  on  the  subject,  of  setting  in  a  low 
temperature  wherein  other  varieties  of  cement  will  surely  freeze. 
No  definite  limits  of  this  action,  however,  have  yet  been  assigned. 


FOUNDATION'S.  353 


Mr.  E.  Leblanc  exposed  cakes  of  Portland-cement  mortar  to  frost 
immediately  after  mixing  and  before  any  setting  had  occurred,  with 
the  result  that  "  they  cracked  deeply  and  in  part  became  disinte- 
grated, but  the  detached  fragments  after  being  thawed  were  found 
perfectly  hard."  In  Mr.  Maclay's  experiments  none  of  the  Port- 
land-cement briquettes  when  mixed  cold  cracked  in  the  slightest 
degree  even  when  exposed  to  as  low  a  temperature  as  11  degrees 
Fahr.,  and  they  all  became  hard  after  thawing.  This  seems  to  be 
the  prevailing  opinion  among  engineers.  Mr.  J.  Dutton  Steele, 
O.E.,  in  discussing  the  paper  of  Mr.  Maclay,  states  that  "  cement- 
mortar  is  not  seriously  impaired  by  being  laid  in  frost,  as  its  prop- 
erty of  setting  is  simply  held  in  suspense  during  the  time  it 
remains  frozen."  Gen.  Q.  A.  Gillmore,  U.S.A.,  in  his  work  on 
Beton,  etc.,  remarks  that  "when  the  temperature  is  not  much 
below  the  freezing  point  during  the  day,  work  may  be  safely  carried 
on  if  care  be  taken  to  cover  over  the  new  material  at  night.  After 
it  has  once  set  and  has  had  a  few  hours  to  harden,  neither  severe 
frost  nor  alternate  freezing  and  thawing  has  any  effect  upon  it." 

In  the  report  of  the  work  performed  at  the  Royal  Testing 
Laboratory  of  Berlin  in  1886  there  is  an  account  of  a  number  of 
experiments  for  ascertaining  the  eifect  of  frost  upon  the  strength 
of  Portland  cement,  both  neat  and  when  mixed  into  mortar  in  the 
proportion  of  3  parts  of  sand  to  1  part  of  cement.  These  tests  were 
made  in  two  distinct  series,  the  first  one  involving  only  a  single 
exposure  to  frost  on  and  during  the  sixth  day  after  mixing,  while 
in  the  second  series  the  briquettes  were  treated  as  follows :  First, 
allowed  to  indurate  for  twenty-four  hours  in  the  air  of  a  warm 
room;  second,  exposed  for  twenty-four  hours  to  a  freezing  tem- 
perature of  from  +  10  degrees  to  +  5  degrees  Fahr. ;  third,  thawed 
four  hours  in  a  warm  room;  fourth,  placed  under  water  until 
tested. 

The  experiments  were  made  with  six  different  brands  of  cement, 
and  for  each  set  of  briquettes  exposed  to  frost  another  similarly 
constituted  set  was  kept  in  temperatures  above  the  freezing  point 
to  serve  as  a  basis  of  comparison  of  tensile  strength.  Upon  test- 
ing the  frozen  and  unfrozen  samples,  it  was  found  that  the  effect 
of  frost  varied  greatly  with  the  quality  of  the  cement;  the  loss  in 
tensile  strength  incurred  by  such  freezing  ranging  after  seven  days 
from  2  to  22  per  cent  in  the  case  of  neat  cement,  and  from  3  to  24 


354  HIGHWAY   CONSTRUCTION. 

per  cent  in  the  case  of  the  mortar  mixed  as  above  described ;  also* 
ranging  after  28  days  from  2  to  12  per  cent  in  the  case  of  neat 
cement,  and  from  1  to  33  per  cent  in  the  case  of  the  mortar.  It 
should  be  noted  particularly  that  the  foregoing  results  were  de- 
rived when  pure,  clean,  and  standard  materials  only  were  used.  On 
the  other  hand,  where  the  cement  was  adulterated  with  30  per  cent 
of  pulverized  slag  from  a  blast-furnace  the  loss  in  strength  by 
freezing  was  much  greater  than  above  given,  especially  in  the  case 
of  the  mortar.  After  seven  days  this  loss  ranged  from  6  to  62  per 
cent,  and  after  28  days  from  21  to  44  per  cent,  standard  sand  hav- 
ing been  used. 

Other  interesting  experiments  with  regard  to  the  effect  of  frost 
on  Portland-cement  mortar  were  carried  out  early  in  1886  at  Ham- 
burg, Germany,  by  Mr.  Moeller,  C.E.,  and  an  account  thereof  is 
contained  in  the  Deutsche  Bauzeitung  for  November  17,  1886. 

The  results  showed  that  Portland-cement  mortar,  whose  time  of 
setting  is  lengthened  by  the  addition  of  sand  or  lime,  or  both,  suf^ 
fers  severely  in  loss  of  tensile  strength  by  the  action  of  frost,  arid 
tnat  such  loss  becomes  greater  as  the  proportion  of  sand  or  lime  is 
increased;  further,  that  a  quick-setting  Portland  cement  will  indu- 
rate in  spite  of  the  frost,  provided  that  it  be  protected  therefronv 
for  two  days  after  having  been  tempered,  and  that  it  be  as  dry  as 
possible  before  exposure  to  the  cold.  It  was  also  found  that  the-' 
mixing  of  such  materials  with  brine  renders  the  mortar  more  capa- 
ble of  resisting  the  influence  of  frost,  and  that  this  statement  like- 
wise holds  true  for  slow-setting  compounds,  such  as  1  part  of  cement,, 
1  part  of  lime,  and  3  parts  of  sand.  Mortars  thus  prepared  and 
mixed  with  fresh  water  instead  of  brine,  and  kept  for  two  days  at 
a  temperature  of  -f-  41  degrees  Fahr.,  and  then  exposed  to  the  frost, 
lost  nearly  all  strength,  so  that  even  after  four  months  pieces  could 
easily  be  broken  off  from  the  briquettes  with  the  fingers;  whereas- 
when  tempered  with  strong  brine  their  strength  after  seven  months 
was  about  fourteen  times  greater.  Accordingly,  if  the  mortar  can 
be  kept  from  freezing  for  a  few  days  by  the  use  of  salt  or  brine, 
so  as  to  allow  the  setting  to  take  place,  much  benefit  is  sure  to  be- 
derived. 

It  may  also  be  deduced  from  these  experiments  that  when  it 
becomes  absolutely  necessary  to  lay  masonry  in  freezing  weather,' 
quick-setting  Portland  cements,  mixed  with  small  proportions  of 


FOUNDATIONS.  355 


sand  and  water,  should  alone  be  employed ;  and  when  a  satisfactory 
quality  of  work  is  expected  or  required,  the  use  of  brine  or  salt 
should  be  resorted  to,  as  well  as  the  protection  of  the  newly-laid 
masonry  at  night  by  means  of  adequate  coverings.  In  case,  how- 
ever, that  the  temperature  is  lower  than  23  degrees  Fahr.  even 
these  precautions  will  not  prevent  more  or  less  damage. 

Under  such  circumstances,  moreover,  it  is  self-evident  that  the 
stones  or  bricks  should  be  free  from  snow  or  ice  and  as  dry  as  prac- 
ticable; also  that  all  the  materials,  including  the  sand  and  cement, 
be  free  from  frost  by  being  kept  at  a  temperature  above  the  freez- 
ing point  for  some  days  before  being  used  in  the  work.  The  safest 
rule,  however,  is  to  cease  operations  with  mortars  of  any  kind  dur- 
ing the  prevalence  of  frost. 

In  a  paper  read  before  the  American  Society  of  Civil  Engineers 
in  July,  1886,  its  author,  Alfred  Noble,  C.E.,  states  that  "  in  the 
construction  of  the  lock  at  the  St.  Mary's  Falls  Canal,  the  laying 
of  masonry  was  discontinued  about  October  20  of  each  year,  on 
account  of  the  frequent  recurrence  of  freezing  weather.  On  the 
last  day  of  the  work  done  in  1877  mortars  made  of  Portland 
cement  and  of  a  good  quality  of  American  natural  cement  were 
used  in  adjoining  portions  of  the  same  wall.  Both  mortars  were 
mixed  in  the  proportions  of  1  cement  to  1  sand,  and  the  masonry 
was  laid  during  a  light  rain.  The  following  spring  the  surface  of 
the  Portland-cement  mortar  was  sound,  showing  perfectly  the 
marks  of  the  rain-drops,  while  the  natural-cement  mortar  was  dis- 
integrated to  a  depth  of  three  or  four  inches."  Mr.  Noble  also 
mentions  a  few  other  cases  where  Portland-cement  mortar  was  used 
in  laying  masonry  during  very  cold  weather  without  affecting  the 
subsequent  induration  of  the  mortar  noticeably.  The  inference  to 
be  drawn  from  his  paper  is  that  if  it  becomes  imperative  to  use 
mortar  in  freezing  weather,  Portland  cement  should  be  used. 

Similar  effects  of  frost  were  also  noticed  by  Mr.  Francis  Colling- 
wood,  C.E.,  on  the  Rosendale-cement  mortars,  mixed  in  the  pro- 
portion of  2  sand  to  1  cement,  used  for  the  masonry  of  the  East 
River  Bridge,  since  he  states  that  "  the  tops  of  the  various  pieces 
of  masonry  were  always  gone  over  carefully  in  the  spring.  The 
concrete  which  had  been  put  in  late  would  usually  be  found  disin- 
tegrated to  a  depth  of  from  one  to  four  inches,  but  below  this  it 
was  found  sound.  The  rule  seems  to  be  that  it  was  unsound  only 


356  HIGHWAY   CONSTRUCTION. 

so  far  as  it  was  exposed  alternately  to  freezing  and  thawing;  and 
wherever  it  had  taken  a  set  before  freezing,  and  had  not  been 
thawed  out  for  some  time,  it  was  sound."  The  experience  of  Mr. 
George  S.  Morison,  C.E.,  with  cements  as  given  in  his  discussion 
of  Mr.  Noble's  paper,  was  in  full  accord  with  -what  was  therein 
stated,  and  in  his  extensive  practice  as  a  designer  and  builder  of 
large  bridges  he  uses  Portland  cement  exclusively  in  all  places 
where  the  mortar  is  liable  to  freeze  before  setting.  Mr.  Eliot  C. 
Clarke,  C.E.,  also  mentioned  that  in  experimenting  with  concretes 
of  Rosendale  and  Portland  cements  which  had  been  exposed  to  the 
weather  for  three  years  he  found  that  the  former  was  injured  and 
disintegrated  from  year  to  year,  while  the  latter  were  not  affected 
at  all. 

Recent  expressions  of  opinion  from  many  other  excellent  au- 
thorities respecting  the  action  of  frost  on  cement-mortars  are  to 
the  same  effect  as  above  recited.  It  is  generally  agreed  that  the 
freezing  of  freshly-prepared  cement-mortar  will  not  destroy  its 
capacity  to  harden  after  becoming  thawed,  but  exactly  how  much 
its  cohesive  and  adhesive  strength  will  thereby  become  impaired 
does  not  appear  to  be  definitely  known;  neither  is  the  effect  of  re- 
peated freezing  and  thawing  very  clearly  pointed  out.  In  our 
winters  it  frequently  happens  that  water  freezes  in  the  shade,  while 
at  the  same  time  ice  melts  in  the  sunlight,  and  hence  under  such 
circumstances  in  a  wall  facing  south  a  slow-setting  mortar  in  the 
face  will  be  alternately  frozen  and  thawed,  while  that  in  the  rear 
will  continue  to  remain  frozen.  This  condition  of  the  work  can- 
not fail  to  be  prejudicial  to  its  ultimate  strength,  and  manifestly 
demands  that  a  strong  and  quick-setting  mortar  be  used  if  the  lay- 
ing of  masonry  be  continued  in  freezing  weather.  Numerous  in- 
stances of  failure  of  walls  and  abutments  built  in  winter  may  be 
cited  which  are  fairly  attributable  to  the  thawing  out  of  the  frozen 
mortar  after  the  warm  weather  has  set  in,  whereby  it  becomes 
almost  as  soft  as  when  first  mixed.  In  such  cases  the  thawed 
mortar  acts  rather  as  a  lubricant  than  as  an  efficient  binding  mate- 
rial, and  if  the  structure  is  then  subjected  to  lateral  forces  of  con- 
siderable magnitude,  deformation  or  failure  is  sure  to  follow  unless 
a  very  wide  margin  of  safety  has  been  allowed  in  the  design. 
When,  however,  the  dimensions  are  fixed  with  reference  to  econ- 
omy and  the  use  of  ordinarily  good  materials  and  workmanship,  as 


FOUNDATIONS.  357 


generally  happens,  the  action  of  frost  becomes  a  very  serious  factor 
in  the  stability  and  durability  of  the  work,  and  therefore  care 
should  be  taken  in  the  proper  selection  of  the  cement.  It  must 
always  be  remembered  that  frozen  cement-mortar  will  not  set  so 
long  as  it  remains  frozen,  and  that  when  it  becomes  thawed  it  is 
simply  in  the  condition  of  material  freshly  mixed,  which,  while  in. 
that  state,  imparts  no  more  strength  to  the  structure  than  sand, 
ashes,  mud,  or  other  inert  matter. 

A  rather  close  observation  for  a  number  of  years  of  the  effects 
of  frost  on  Buffalo  and  Akron  cement-mortars,  mixed  in  the  pro- 
portion of  two  sand  to  one  cement  and  three  sand  to  one  cement, 
leads  to  the  conclusion  that  such  mortars  entirely  disintegrate  to  a 
depth  of  several  inches  in  exposed  joints  of  masonry  laid  in  cold 
weather;  also  that  when  used  as  coatings  or  renderings  of  rough 
stone  surfaces  a  flaking  thereof  occurs  by  frost  which  leads  to 
rapid  disintegration.  If  it  is  imperative  that  masonry  be  built  in 
freezing  weather,  a  quick-setting  Portland  cement-mortar  should 
be  used,  instead  of  such  as  is  prepared  with  natural  cements; 
also  that  even  when  Portland  cement  is  used  with  brine,  work 
should  be  suspended  when  the  temperature  is  lower  than  25  degrees 
Fahr.,  if  good  results  are  to  be  expected ;  and  finally,  smaller  pro- 
portions of  sand  shoud  be  used  than  during  the  prevalence  of  higher 
temperatures. 

508.  The  standard  of  tensile  strength  required   by   German 
engineers  of  Portland-cement  mortar,  prepared  by  mixing  one  unit 
of  weight   of  cement  with  three  like  units  of  normal  sand,  and 
four  tenths  of  such  a  unit  of  clean  fresh  water,  and  tested  after  an 
exposure  of  one  day  in  air  and  twenty-seven  days  in  water,  is  227 
pounds  per  square  inch  and  a  resistance  to  compression  of  2300 
pounds  per  square  inch. 

509.  English  Specifications  for  Portland  Cement. — The  follow- 
ing is  a  summary  of  the  specifications  used  by  Mr.  Henry  Faija, 
an  accepted  English  authority : 

Fineness.— To  be  such  that  the  cement  will  pass  through  a 
sieve  having  625  holes  (252)  to  the  square  inch,  and  leave  only  10 
per  cent  residue  when  sifted  through  a  sieve  having  2500  holes 
(502)  to  the  square  inch. 

Expansion  or  Contraction. — A    pat  made  and  submitted  to 


358  HIGHWAY    CONSTRUCTION. 

moist  heat  and  warm  water  at  a  temperature  of  about  100  degrees 
Fahr.  shall  show  no  sign  of  blowing  in  twenty-four  hours. 

Tensile  Strength. — Briquettes  of  slow-setting  Portland,  which 
have  been  gauged,  treated,  and  tested  in  the  prescribed  manner,  to 
cany  an  average  tensile  strain,  without  fracture,  of  at  least  17G 
pounds  per  square  inch  at  the  expiration  of  three  days  from  gaug- 
iug;  and  those  tested  at  the  expiration  of  seven  days  to  show  an 
increase  of  at  least  50  per  cent  over  the  strength  of  those  at  three 
days,  but  to  carry  a  minimum  of  350  pounds  per  square  inch. 

For  quick-setting  Portland  at  least  176  pounds  per  square  inch 
at  three  days,  and  an  increase  at  seven  days  of  20  to  25  per  cent, 
but  a  minimum  of  400  pounds  per  square  inch.  Very  high 
tensile  strengths  at  early  dates  generally  indicate  a  cement  verging 
on  an  unsound  one." 

510.  Data  for  Estimates. — The  following  data  will  be  found 
useful  in  estimating  the  amounts  of  the  different  ingredients  neces- 
sary to  produce  any  required  quantity  of  mortar : 

One  barrel  of  lime  (230  pounds)  will  make  about  2^  barrels  (0.3 
cubic  yard)  of  stiff  lime-paste.  One  barrel  of  lime-paste  and  three 
barrels  of  sand  will  make  about  three  barrels  (0.4  cubic  yard)  of 
good  lime-mortar.  One  barrel  of  unslaked  lime  will  make  about 
6.75  barrels  (0.95  cubic  yard)  of  one  to  three  mortar. 

A  barrel  of  Portland  cement  weighs  400  pounds  gross,  or  about 
375  net.  Hudson  River  Rosendale  weighs  300  pounds  net  per  bar- 
rel. Western  Rosendale  weighs  265  pounds  net  per  barrel. 

A  barrel  of  Rosendale,  as  packed  at  the  manufactories  on  the 
Hudson  will  measure  from  1.25  to  1.40  barrels  if  measured  loose. 
A  barrel  of  Western  Rosendale  will  make  about  1.1  barrels  if 
measured  loose.  A  commercial  barrel  of  Portland  will  make  about 
1.2  barrels  if  measured  loose. 

One  cubic  foot  of  dry  cement  (shaken  down  but  not  compressed) 
mixed  with  0.33  cubic  foot  of  water  will  give  0.63  cubic  foot  of  stiff 
paste.  One  barrel  (300  pounds)  of  finely  ground  Rosendale  cement 
will  make  from  3.70  to  3.75  cubic  feet  of  stiff  paste;  or  79  to  83 
pounds  of  cement-powder  will  make  about  one  cubic  foot  of  stiff 
paste.  Volume  for  volume,  Portland  will  make  about  the  same 
amount  of  paste  as  Rosendale;  or  100  pounds  of  Portland  will  make 
a< cubic  foot  of  stiff  mortar. 

511.  Machine-mixed  mortars  and  concretes  are  superior  to  hand- 


FOUNDATIONS.  359 


•mixed.  In  hand-mixing  the  first  drawback  is  the  liability  to  error 
in  measuring  out  correct  and  uniform  proportions  of  prescribed 
materials.  Mortar  men  make  mistakes  which  generally  happen  to 
be  against  the  proper  proportions  of  cement.  The  quantity  of  sand 
will  also  vary  according  to  whether  it  is  measured  in  wet  or  dry 
condition,  packed  or  loose.  Next  the  workmen  fail  to  intermix  the 
cement  and  sand  thoroughly  before  adding  the  water — an  important 
point.  Again,  they  will  ease  up  on  the  labor  required  to  mix  all 
well  together  after  applying  water,  and  to  facilitate  the  operation 
will  over-dose  the  water.  A  further  error  occurs  in  assuming  that 
all  barrels  of  cement  contain  equal  quantities.  The  necessity  of  a 
close  supervision  will  be  recognized  in  these  particulars. 

512.  Specifications  for  Concrete  (Boston). — The  American  cement- 
concrete  shall  be  made  of  one  part  of  American  hydraulic  cement, 
two  parts  of  clean,  sharp  sand,  and  five  parts  of  clean  broken  stone 
or  screened  gravel-stones  by  measure. 

The  Portland-cement  concrete  shall  be  made  of  one  part  Port- 
land cement,  three  parts  of  clean,  sharp  sand,  and  seven  parts  of 
clean  broken  stone  or  screened  gravel-stones  by  measure. 

The  stone  for  the  concrete  shall  be  free  from  clay,  dirt,  or  other 
objectionable  material;  no  stone  shall  be  larger  than  2-j-  inches  and 
but  very  few  less  than  J-  inch  in  their  greatest  dimensions. 

The  mixing  shall  be  done  in  proper  boxes,  in  a  manner  satisfac- 
tory to  the  engineer;  and  after  the  materials  are  wet  the  work  must 
proceed  rapidly  until  the  concrete  is  in  place  and  is  so  thoroughly 
rammed  that  water  flushes  to  the  furface  and  all  the  interstices  be- 
tween the  stones  are  entirely  filled  with  mortar.  The  surface  of 
the  concrete  foundation  must  be  floated  and  made  exactly  parallel 
with  the  crown  of  the  pavement  to  be  laid,  and  must  be  suitably 
protected  from  the  action  of  the  sun  and  wind  until  set.  It  shall 
be  allowed  to  set  a  sufficient  time,  to  be  determined  by  the  engin- 
eer, before  walking  over  or  working  upon  it  shall  be  allowed. 

513.  Specifications  for  Concrete  (Berlin). — The  concrete  is  to  be 
prepared  from  a  mixture  of  cement  and  sand  or  a  mixture  of  cement, 
;sand,  and  broken  granite  or  limestone.     In  making  it  at  least  one 
barrel  of  cement  in  the  standard  proportion  of  180  kilos  gross  or 
170  kilos  net  weight  is  to  be  used  with  one  cubic  meter  of  sand  or  of 
.sand  and  stone.     The  proportions  of  sand  and  broken  stone  are  to 
be  .determined  in  each  case  by  the  inspector.     If  in  exceptional 


360  HIGHWAY    CONSTRUCTION. 

cases  a  greater  proportion  of  cement  is  employed  to  obtain  quicker 
setting,  a  corresponding  payment  will  be  made  for  each  barrel  used,, 
as  given  in  the  schedule  of  prices. 

The  cement  is  to  be  weighed  whenever  the  inspector  desires. 
In  order  that  the  proportions  may  exactly  conform  to  the  specifica- 
tions, the  sand  or  mixture  of  sand  and  stone  is  to  be  measured  in. 
boxes  holding  exactly  one  half  or  one  cubic  meter. 

The  mixing  is  done  on  a  platform  that  must  be  30  centimeters 
(11.8  inches)  larger  all  around  than  the  bottom  of  the  measuring- 
boxes.  The  sides  are  to  be  provided  with  strips  to  prevent  the 
falling  of  the  material.  In  order  to  insure  regular  work  at  least 
five  mixing-boards  are  to  be  set  up  at  each  place  of  working. 

Sand  and  cement  are  to  be  twice  mixed  dry  before  water  is 
added.  After  the  addition  of  the  water  the  mass  must  be  immedi- 
ately worked  to  a  stiff  condition.  During  the  preparation  of  the 
concrete,  all  the  foreign  bodies  in  the  cement  or  sand  are  to  be 
carefully  removed.  If,  during  the  process  of  mixing,  a  portion  of 
the  concrete,  of  sand  or  stone,  falls  from  the  platform,  it  must  not 
be  again  added  to  the  mass  and  used  in  the  concrete,  but  must 
be  removed. 

Laying  the  Concrete. — In  order  to  insure  the  exact  formation 
of  the  concrete  foundation,  a  series  of  templates  are  to  be  laid  on 
the  road-bed  from  4  to  5  meters  apart  and  parallel  to  the  axis  of 
the  street.  The  greatest  care  must  be  taken  to  have  these  templates 
at  the  proper  height,  and  all  out  of  alignment  must  be  immedi- 
ately removed. 

When  the  road-bed  has  been  finally  brought  to  the  proper  grade* 
the  concrete  is  to  be  laid  between  the  templates  and  thoroughly 
tamped  and  worked  into  a  profile  corresponding  to  that  of  the 
finished  street  surface. 

Use  of  the  Concrete  after  its  Preparation. — While  the  concrete 
is  setting,  it  is  to  be  sprinkled  with  water  so  that  the  surface  is 
continually  moist,  and  as  long  as  it  remains  soft  the  work  must  ba 
protected  by  suitable  guards  from  intruders. 

No  concrete  shall  be  prepared  at  a  temperature  below  2  degrees 
Reaumur  (36£  degrees  Fahr.).  Concrete  just  laid  is  to  be  pro- 
tected for  two  days,  when  frost  begins,  by  a  co.vering  of  mats  or 
bundles  of  straw. 

The  foundation  must  have  exactly  the  same  profile  as  the  upper 


FOUNDATIONS.  361 


surface  of  the  finished  pavement  is  to  receive.  It  is  especially 
necessary  that  the  surface  be  free  from  all  inequalities,  elevations 
as  well  as  depressions.  Work  must  not  begin  on  the  construction 
of  the  foundation  until  the  inspector  has  definitely  stated  that  the 
work  on  the  roadbed  has  been  finished  in  the  manner  prescribed 
in  the  regulations. 

514.  Specifications  for  Concrete    (New  York). — One   part    of 
American   cement,  equal   to   the   best  quality  of  freshly  burned 
Rosendale  cement,  two  parts  of  clean,  sharp,  washed  sand,  free 
from  clay,  to  be  thoroughly  mixed  dry  and  then  made  into  mortar 
with  the  least  possible  amount  of  water;  to  this  shall  be  added 
three  parts  of  sound  stone,  broken  with  a  hammer,  the  largest  of 
which  will  pass  through  a  2-inch  ring,  the  broken  stone  to  be  wet 
before  being  added  to  the  mortar.     The  whole  mass  shall  then  be 
shoveled  over  until  it  is  thoroughly  mixed  before  it  is  put  in  place : 
it  shall  then  be  put  in  place  and  rammed  until  it  is  thoroughly 
compacted  and  has  a  clean  mortar  surface. 

The  whole  operation  of  mixing  and  laying  each  batch  will  be 
performed  as  expeditiously  as  possible,  by  the  employment  of  a 
sufficient  number  of  skilled  men. 

The  upper  surface  will  be  made  exactly  parallel  with  the  pave- 
ment when  laid,  and,  if  necessary,  will  be  protected  from  the  action 
of  the  sun  and  wind  until  set. 

No  concrete  will  be  allowed  to  be  used  which  has  been  mixed 
more  than  three  hours. 

The  concrete  shall  be  laid  to  a  depth  of  6  inches. 

515.  Concrete  for  Foundations,  as  used  in  Paris.— The  propor 
tions  by  bulk  are : 

Cement ...e 1    Part 

Sand 4    Parts 

Gravel 6 

Water H    ' 

or  one  of  cement  to  ten  of  sand  and  gravel. 

The  concrete  is  mixed  on  a  large  mortar-board,  the  mixers  mov- 
ing the  board  ahead  as  the  work  advances,  and  never  being  more 
than  a  few  feet  from  the  spot  where  the  concrete  is  to  be  placed. 

A  square  wooden  form  is  placed  on  the  mortar-board;  into  this 
is  dumped  successively,  in  the  order  named,  2  barrows  of  gravel. 


362  HIGHWAY    CONSTKUCTIOJST. 

£  sack  of  cement,,  1  barrow  of  gravel,  \  sack  of  cement,  2  barrows 
of  sand.  The  form  is  then  removed,  and  the  mass  turned  over  dry 
with  the  shovel  by  two  men  working  side  by  side.  It  is  then 
turned  a  second  time  by  the  two  men,  while  a  third  sprinkles  on 
the  water  from  a  pot.  The  mass  is  then  turned  over  a  third  time, 
and  shoveled  from  the  board  directly  into  place. 

This  concrete  sets  quickly,  and  every  evening  the  surface  of  that 
laid  during  the  day  is  covered  with  a  thin  coat  of  pure  cement. 

516.  Specifications  for  Preparation  of  Roadbed. — The  subsoil 
or  other  matters  (be  it  earth,  rock,  or  other  material)  shall  be 
excavated  and  removed  to  a  depth  of  inches  below  the  top  line 
•of  the  proposed  pavement.  Should  there  be  any  spongy  material, 
vegetable  or  other  objectionable  matter,  in  the  bed  thus  prepared, 
-all  such  material  must  be  entirely  removed,  and  the  space  filled 
with  clean  gravel  or  sand  carefully  rammed. 

The  roadbed  shall  be  truly  shaped  and  trimmed  to  the  required 
cross-section  and  grade,  and  rolled  to  ultimate  resistance  with  a 
roller  weighing  not  less  than  ten  tons;  such  portions  of  the  road- 
bed as  cannot  be  reached  by  the  roller  shall  be  consolidated  with 
hand  rollers  or  tampers. 

Note. — The  employment  of  ashes,  garbage,  or  other  objectionable 
matter  should  not  be  permitted  for  filling  on  the  streets  of  cities 
and  towns. 

Kock  shall  be  excavated  to  a  depth  of  2  feet  below  the  level  of 
the  finished  grade,  and  the  space  so  excavated  shall  be  refilled  to 
subgrade  level  with  gravel,  steam  ashes,  or  other  approved  material, 
and  thoroughly  consolidated. 

516a.  Foundation  employed  in  Liverpool.— The  foundation  em- 
ployed in  Liverpool  for  heavy-traffic  pavements  is  described  by  Mr. 
P.  H.  Boulnois,  City  Engineer,  as  f  ollows : "  The  ground  having  been 
prepared  in  the  usual  way,  and  the  channel  (gutter)  and  curb  stones 
fixed  in  position,  a  stratum  of  stones  (which  should  by  preference  be 
of  a  non-absorbent  character),  broken  so  as  to  pass  all  ways  through  a 
3-inch  ring,  is  spread  evenly  over  the  surface  of  the  ground,  and 
upon  this  is  placed  a  layer  of  cement  mortar  mixed  in  the  propor- 
tions of  one  of  Portland  cement  to  six  of  fine,  sharp,  clean  gravel 
in  the  method  to  be  described  hereafter.  Upon  this  layer  of  mor- 
tar is  placed  another  layer  of  broken  stone — the  whole  of  the  stones 


FOUNDATIONS.  363 


in  each  layer  to  be  thoroughly  watered  while  the  work  is  proceed- 
ing— and  this  stone  is  forced  into  the  interstices  of  the  first  layer 
by  the  use  of  flat  beaters  of  wrought  iron,  weighing  1 6  pounds 
each,  shaped  like  square  shovels,  with  handles  at  an  angle  of  33 
degrees. 

"  This  process  is  repeated  until  the  proper  level  and  contour  is 
reached,  and  the  surface  is  finished  off  parallel  to  the  exact  curva- 
ture of  the  carriageway. 

"The  foundation  thus  prepared  is  left  until  the  concrete  is  suffi- 
ciently set  or  hardened  to  receive  the  pavement,  which,  if  possible, 
should  not  be  less  than  ten  days,  although  this  period  may  be 
shortened,  where  the  exigencies  of  the  traffic  render  it  imperative,  by 
strengthening  the  proportion  of  cement  to  gravel,  care  to  be  taken 
in  all  cases  to  periodically  water  the  surface  of  the  concrete  to  assist 
the  ultimate  hardening,  and  in  very  hot  weather  it  is  advisable  to 
cover  the  surface  of  the  concrete  with  old  cement-bags  saturated 
with  water. 

"  The  proportions  of  broken  stone,  gravel,  and  cement  used  in 
such  a  concrete  are  as  follows : 

"  Before  Mixing. — Broken  stone,  8  parts;  gravel,  6  parts;  cement, 
1  part. 

"  After  Mixing. — Broken  stone  and  gravel,  mixed  together,  11 
parts;  cement,  1  part;  three  parts  of  gravel  having  been  expended 
in  filling  the  interstices  of  the  stones. 

"  The  method  adopted  for  insuring  that  the  cement  mortar  shall 
contain  the  proper  proportions  as  carried  out  in  Liverpool  is  as 
follows:  An  apparatus  is  used  consisting  of  a  set  of  double  mixing- 
boards,,  each  7  feet  by  3|  feet,  having  1-J-inch  deal  sides  and  back 
9  inches  high,  and  1^-inch  deal  bottom  lined  with  sheet  iron.  A 
partition  in  the  centre  divides  the  board  into  two  compartments; 
at  the  back  of  each  compartment  is  a  box  for  measuring  the  gravel, 
with  a  capacity  of  1  cubic  foot,  14  inches  square  at  the  top,  10 
inches  square  at  the  bottom,  and  12  inches  deep.  It  is  hinged  to 
the  back  of  the  board  by  strong  iron  eyes  and  bolts. 

"  Any  number  of  mixing-boards  being  placed  side  by  side,  about 
1  foot  apart,  the  water-supply  is  arranged  as  follows  :  A  length  of 
flexible  hose  is  attached  at  one  end  to  the  nearest  hydrant,  and  at 
the  other  end  to  the  ball-tap  of  a  sheet-iron  regulating-cistern, 


364  HIGHWAY    CONSTRUCTION". 

containing  18  gallons,  fixed  on  a  light  angle-iron  frame,  about  4 
feet  from  the  ground  to  the  bottom  of  the  cistern;  this  is  placed  at 
one  end  of  the  series  of  mixing-boards.  Opposite  to.  the  inlet-pipe 
is  an  outlet-pipe  of  flexible  tubing  attached  to  the  cistern  by  brass 
unions;  water  is  conveyed  through  this  pipe  to  a  horizontal 
wrought-iron  pipe,  7  feet  long,  supported  upon  light  iron '  stand- 
ards placed  over  the  back  of  each  mixing-board.  Attached  to  this 
pipe  is  a  pair  of  brass  swivel  rose-ended  pipes  with  stop-taps;  these 
roses  are  so  arranged  as  to  discharge  the  water  in  a  gentle  rain- 
like  spray  over  the  centre  of  each  mixing-compartment.  This  ar- 
rangement may  be  extended  to  any  number  of  boxes,  the  service- 
pipes  being  connected  by  flexible  tubing. 

"  The  cement  is  measured  in  light  iron  bowls  having  a  capacity 
of  -j-  cubic  foot. 

"  The  usual  arrangement  for  mixing  concrete  is  as  follows  :  The 
mixing-boards  are  placed  with  their  backs  to  a  heap  of  gravel,  the 
cement  being  stored  at  one  end,  also  at  the  back  of  the  boxes;  a 
laborer  with  a  mixing-shovel  is  detailed  off  to  each  mixing-com- 
partment; a  man  at  the  back  fills  each  measuring-box  with  gravel; 
the  mixer  in  front  tips  over  this  box  with  his  shovel,  emptying  the 
gravel  into  the  mixing-board;  a  boy  brings  a  bowlful  of  cement 
from  the  store  and  spreads  it  over  the  gravel;  the  mixer  turns  over 
the  contents  of  his  board  until  the  cement  and  gravel  are  thor- 
oughly mixed  in  a  dry  state;  he  then  turns  the  tap  of  the  rose- 
pipe,  and  allows  the  water  to  flow  over  the  mixture  until  sufficient 
moisture  for  setting  is  obtained,  the  quantity  of  water  used  vary- 
ing with  the  dampness  of  the  gravel.  The  concrete  is  now  thrown 
into  wheelbarrows  and  conveyed  to  its  destination.  One  mixer  in 
nine  hours  can  turn  out  ninety  such  mixings,  which  are  equal  to  6£ 
cubic  yards." 

516b.  Specifications  for  Concrete  (Chicago). — PROPORTIONS. — 
One  part  cement,  three  parts  sand,  seven  parts  broken  stone;  sand 
and  cement  mixed  dry;  water  then  added  to  make  a  stiff  mortar, 
to  which  the  stone  is  immediately  added  and  mixed  (water  being 
added  if  necessary)  until  each  particle  of  stone  is  covered  with 
mortar.  The  concrete  is  deposited  in  one  layer  and  rammed  to  a 
true  and  smooth  surface.  The  subgrade  is  kept  moist,  and  the 


FOUNDATIONS.  365 


concrete  is  sprinkled  as  necessary  and  left  exposed  for  at  least 
seven  days. 

MATERIALS. — Portland  Cement,  92  per  cent  passing  through 
a  No.  100  sieve,  passing  the  "boiling  test/7  setting  in  45  minutes 
or  more;  tensile  strength  (neat)  400  pounds  in  7  days,  175  pounds 
for  1  cement  to  3  sand,  with  15  per  cent  increase,  in  28  days. 

Sand,  clean,  dry;  grains  ^  inch  and  less,  not  more  than  30  per 
cent  voids;  weighing  109  pounds  per  cubic  foot. 

Stone,  limestone,  clean,  between  1£  inches  and  1  inch  in  largest 
dimensions. 


CHAPTER  X. 
RESISTANCE  TO  TRACTION. 

517.  The  resistance  to  traction  on  highways  is  occasioned  (1)  by 
the  want  of  uniformity  in  the  surface  of  the  road,  the  weight  of  the 
load  having  to  be  lifted  over  the  projecting  points  and  out  of  hol- 
lows and  ruts,  thus  diminishing  the  effective  load  which  the  horse 
may  draw  to  such  as  it  can  lift. 

(2)  The  want  of  strength  of  the  roadbed  itself,  however  free 
its  surface  may  be  from  asperities  or  cavities,  if  its  substructure 
be  of  such  a  nature  that  it  will  yield  to  the  pressure  of  the  wheels, 
adds  another  impediment  to  the  movement  of  a  load  over  it,  with 
the  additional  disadvantage  that  while  the  horse  is  endeavoring  to 
lift  the  load  from  a  cavity  or  hollow,  the  fulcrum,  which  in  the 
first  case  was  supposed  to  be  fixed  and  rigid,  is  in  the  latter  yielding 
and  variable,  subjecting  the  horse  to  the  constant  effort  of  lifting, 
instead  of  simply  drawing. 

518.  Want  of  Uniformity  in  the  Surface. — The  power  required 
to  draw  a  wheel  over  a  stone  or  any  obstacle,  such  as  S  in  Fig.  36, 
may  be  thus  calculated.     Let  P  represent  the  power  sought,  or 


A  b 

FIG.  36. 

that  which  would  just  balance  the  weight  on  the  point  of  the 
stone,  and  the  slightest  increase  of  which  would  draw  it  over. 

36G 


RESISTANCE   TO  TRACTION".  367 

This  power  acts  in  the  direction  CP  with  the  leverage  of  BO 
or  DE.  Gravity,  represented  by  W,  resists  in  the  direction  CB 
with  the  leverage  of  BD.  The  equation  of  equilibrium  will  be 
P  x  CB  =  W  X  BD,  whence 


CB  ~  CD  -AB 

Let  the  radius  of  the  wheel  —  CD  =  26  inches,  and  the  height 
of  the  obstacle  =  AB  =  4  inches.  Let  the  weight  W  =  500 
pounds,  of ,  which  200  pounds  may  be  the  weight  of  the  wheel  and 
300  pounds  the  load  on  the  axle.  The  formula  then  becomes 


„       ,_A  |/676  -  484        KA_  13.85        0,  .  „  , 

P  =  500  2L_  --  _-  =  500  -—  —  =  314.7  pounds. 
— 


—     4 


The  pressure  at  the  point  D  is  compounded  of  the  weight  and 
the  power,  and  equals 


C'D  2S 

W  —£  =  500  X  z=  =  591  pounds, 


and  therefore  acts  with  this  great  effect  to  destroy  the  road  in  its 
collision  with  the  stone,  in  addition  there  is  to  be  considered  the  effect 
of  the  blow  given  by  the  wheel  in  descending  from  it.  For  minute 
accuracy  the  non-horizontal  direction  of  the  draught  and  the 
thickness  of  the  axle  should  be  taken  into  account.  The  power 
required  is  lessened  by  proper  springs  to  vehicles,  by  enlarged 
wheels,  and  by  making  the  line  of  draught  ascending. 

519.  Resistance  of  Penetration.  —  This  resistance  is  that  of  a 
medium  distributed  over  the  submerged  portion  of  the  circum- 
ference of  a  wheel,  in  advance  of  the  perpendicular  line  drawn 
from  the  centre  of  the  wheel  to  the  plane  of  the  road.  The 
following  investigation  furnishes  a  formula  for  calculating,  with 
sufficient  degree  of  accuracy,  the  resistance  of  gravel,  loose  stones, 
soft  earth,  or  clay. 

Let  AOB,  Fig.  37,  be  a  wheel  drawn  over  the  horizontal 
surface  CDE  of  the  road,  in  the  direction  OF,  and  let  the  road 
be  of  such  a  consistency  that  the  wheel  penetrates  to  the  depth 


368 


HIGHWAY    CONSTRUCTION. 


DB  below  the  surface,  leaving  a  track  BG  behind  it.  The  arc 
JBCis  the  submerged  pcfrtion  of  the  circumference,  and  it  may  be 
assumed  to  be  identical  with  the  chord  of  the  arc  BC.  Now  the 
resistance  is  distributed  over  the  surface  BC,  and  it  may  be  taken 


as  acting  on  this  surface  perpendicularly  to  the  plane  of  the  road, 
or  vertically  and  directly  opposed  to  the  gross  weight,  consisting 
of  the  weight  of  the  wheel  and  the  load  upon  it.  To  simplify  the 
investigation,  let  it  be  supposed  that  the  upper  portion  of  the  road 
is  homogeneous,  as  clay  or  sand;  then  the  resistance  to  penetra- 
tion is  nothing  at  the  surface,  and  it  increases  as  the  depth;  and 
the  upward  resistance  along  the  line  of  submersion,  BG,  is  a 
maximum  at  B  and  it  vanishes  at  (7,  and  the  varying  intensity  of 
the  graduated  pressure  may  be  represented  by  an  isosceles  triangle, 
of  which  the  centre  of  gravity,  H,  situated  at  one  third  of  its  length, 
BH,  from  the  base,  B,  is  also  the  centre  of  resistance,  and  therefore 
also  the  centre  of  pressure  under  the  load;  and  the  radial  line  OH 
is  the  resultant  of  the  pressure  of  the  load,  measured  in  force  and 
direction  by  the  vertical  01,  and  the  tractive  force,  measured  by 
the  horizontal  line  HI  or  OK.  But  the  vertical  01  may  be  taken 
as  equal  to  the  radius  OB,  and  the  horizontal  HI  may  be  taken 
as  one  third  of  the  semi-chord  of  submersion  CD',  whence  the 
proportion 

Load  :  tractive  force  : :  OB  :  CD  : :  radius  of  wheel  :  J  semichord; 


RESISTANCE   TO   TRACTION. 


369 


and  the  resistance  to  traction  is  equal  to  the  product  of  the  load 
by  the  third  of  the  semichord  divided  by  the  radius  of  the  wheel. 
But  the  length  of  the  semichord  CD  may  be  more  easily  deter- 
mined by  calculation  from  the  measured  depth  of  submersion  DB. 
It  is  equal  to  the  square  root  of  the  products  of  the  segments  into 
which  the  diameter  AB  is  divided  by  the  plane  of  the  road  CDE, 
or  to  \/AJ)~x  DB\  an(i  ^ne  whole  of  the  calculations  is  embraced 
by  the  equation 


Tractive  force  OK  =     X 


WVADxBD 
OB 


(1) 


The  work  done  in  compressing  the  material  of  the  road  is 
easily  indicated  diagrammatically,  by  supposing  the  wheel  to  advance 
through  a  space  equal  to  the  semichord  CD,  or  the  length  of  the 
-submersion.  Thus,  in  Fig.  38,  the  wheel  AB  is  supposed  to  roll 


FIG.  38. 


FIG.  39- 


forward  and  to  occupy  the  position  A'B' .  The  work  done  in 
compressing  the  road  is  proportioned  to  the  four-sided  area 
BCC'B',  comprised  between  the  circumferential  segments  #£7  and 
B'C',  and  this  area  is,  by  the  properties  of  the  circle,  equal  to  the 
original  rectangular  area,  B  DOB'. 

Now,  suppose  a  wheel  ABA,  Fig.  39,  of  larger  diameter  with 
the  same  gross  weight,  to  travel  over  the  same  surface.  It  is 
obvious  that,  if  it  could  sink  to  the  same  depth,  db,  as  that  for  the 
smaller  wheel,  the  length  of  immersion,  dc,  would  be  increased, 
and  the  rectangle,  db  X  dc,  representing  work,  would  be  greater 


370  HIGHWAY    CONSTRUCTION. 

than  that  performed  by  the  smaller  wheel  in  the  first  example. 
Such  a  supposition  cannot  be  admitted  :  the  depth  of  immersion, 
dB,  for  the  larger  wheel,  must  be  less  than  that,  db,  for  the  smaller 
wheel,  though  the  length  of  immersion  dC,  must  be  greater  than  that, 
dc,  for  the  smaller  wheel,  but  not  so  much  greater  as  if  the  wheel 
were  sunk  to  the  first  depth,  db. 

In  fine,  larger  wheels  sink  less  but  spread  more  into  the  surface 
than  the  smaller  wheels,  in  such  proportion  that  the  area  of  the 
rectangle  representing  work  of  submersion  is  constant  for  all  sizes. 
of  wheels.  In  this  instance,  accordingly,  the  rectangle  db  X  dc  = 
the  rectangle  dB  X  dC. 

It  might  be  thought  that,  on  this  principle  of  the  constancy  of 
the  work  of  submersion,  in  a  soft  road,  the  resistance  to  traction 
must  be  the  same  for  all  diameters  of  wheels.  But,  as  the  rect- 
angle of  work  is  spread  over  a  longer  space,  dO,  for  the  larger 
wheel,  than  the  space,  dc,  for  the  smaller  wheel,  it  follows,  on  the* 
contrary,  that  the  resistance  or  force  of  traction  varies  in  some 
proportion  inversely  as  the  diameter,  being  less  as  the  diameter  is 
greater.  This  conclusion  accords  with  experience;  but  though  the 
actual  law  of  variation  may  not  be  strictly  deducible  in  the  line  of 
reasoning  here  traced,  it  is  nevertheless  useful  to  carry  the  reason- 
ing to  its  logical  conclusion.  Let  a  and  A  be  the  diameters  respec- 
tively of  the  smaller  and  the  larger  wheels,  b  and  B  the  depths  of 
immersion,  and  c  and  C  the  lengths  of  immersion,  or  dc  and  DC, 
respectively.  As  already  stated,  the  areas  of  immersion  are  equal 
to  each  other,  or 


(2) 


Also,  the  values  of  c  and  C  are,  by  the  properties  of  the  circle,  ex- 
pressible by  the  products  Vab  and  VAB,  for  all  cases  that  need 
occur  in  practice;  and,  by  substitution  in  the  equation  (2), 


.......     (3) 

and,  squaring  both  sides, 

.    .    .    ....    (4) 


RESISTANCE    TO    TRACTION. 


Finally,  extracting  the  cube  root  of  each  side  of  this  equation  (4), 
the  equation  (5)  is  obtained, 


........     (5) 

which  may  be  developed  into  the  proportion 

b'\Br.VA\n\  .......     (6) 

showing  that  the  depth  of  immersion  varies  as  the  cube  root  of  the 
diameter.  But,  as  be  —  BC,  and  b:  B:  :  C:c,  then, 

C:c::V2:Va,  .......     (7) 

showing  that  the  length  of  immersion  is  as  the  cube  root  of  the 
diameter.  It  has  already  been  seen  that  the  force  of  traction  is  as 
the  length  of  immersion;  therefore,  finally, 

520.  The  circumferential  or  rolling  resistance  of  wheels  to 
traction  on  a  level  road  is  inversely  proportional  to  the  cube  root 
of  the  diameter. 

On  this  principle  of  resistance,  it  follows  that,  to  reduce  the 
rolling  resistance  of  a  wheel  one  half,  for  instance,  the  diameter 
must  be  enlarged  to  eight  times  the  primary  diameter. 

The  deduction  of  M.  Morin,  that  the  resistance  varies  simply  in 
the  inverse  ratio  of  the  diameter  of  the  wheel,—  so  that,  for  exam- 
ple, a  wheel  of  twice  the  diameter  would  only  incur  half  the  resist- 
ance, —  has  been  generally  accepted.  But  this  deduction  is  not 
supported  by  the  foregoing  analysis  of  forces,  and  there  is  good 
reason  for  renouncing  it,  in  the  more  recent  experiments  of  M. 
Dupuit.  He  placed  model  wheels  or  rollers  of  various  diameters  at 
the  summit  of  an  inclined  plane,  succeeded  by  a  horizontal  plane, 
on  which  they  rolled  down  by  the  force  of  gravity  and  arrived  at  a 
state  of  rest  after  having  expended  the  energy  acquired  in  falling 
through  the  height  of  the  plane.  From  these  and  other  experi- 
ments he  drew  the  following  deductions  : 

On  macadamized  roads  in  good  condition,  and  on  uniform  sur- 
faces generally, 

(1)  The  resistance  to  traction  is  directly  proportional  to  the 
pressure. 


372 


HIGHWAY    CONSTRUCTION. 


(2)  It  is  independent  of  the  width  of  the  tire. 

(3)  It  is  inversely  as  the  square  root  of  the  diameter. 

(4)  It  is  independent  of  the  speed. 

M.  Dupuit  admits  that  on  paved  roads  which  give  rise  to  con- 
stant concussion,  the  resistance  increases  with  the  speed,  whilst  it 
is  diminished  by  an  enlargement  of  the  tire  up  to  a  certain  limit. 

The  resistance  produced  by  the  hollows  between  the  stones  of  a 
pavement  is  of  a  different  character.  According  to  M.  Gerstner, 
the  resistance  arising  from  such  a  surface  is  directly  proportional 
to  the  load,  to  the  square  of  the  velocity,  and  to  the  ratio  of  the 
width  of  the  cavity  to  the  radius  of  the  wheel,  and  inversely  pro- 
portional to  the  width  of  the  paving-stones. 

521.  Friction. — The  resistance  of  friction  arises  from  the  rub- 
bing of  the  wheels  against  the  surfaces  with  which  they  come  in 
contact,  and  will  always  exist.     The  friction  of  surfaces  is  variable, 
and  can  be  determined  only  by  experiment.     Friction  of  the  axles 
and  resistance  of  the  air  are  causes  of  resistance  to  motion  but 
their  consideration  may  be  neglected,  as  their  effects  are  constant, 
and  independent  of  the  imperfections  of  the  road. 

522.  Many  experiments  have  been  made  at  various  times  to 
ascertain,  in  functions  of  the  quality  and  condition  of  the  road-sur- 
faces, the  measure  of  the  tractive  force,  or  the  force  required  to 
overcome  the  resistances  which  oppose  themselves  to  tfie  movement 
of  a  vehicle  along  horizontal  roads  of  different  degrees  of  smooth- 
ness and  hardness  and  covered  with  different  materials. 

Table  L  presents  the  results  of  those  experiments.    The  frac- 

TABLE  L. 

RESISTANCE  TO  TRACTION  ON  DIFFERENT  ROAD-SURFACES. 
(RUDOLF  BERING). 


Character  of  Road. 

Resistance 
in  Terms  of 
Load. 

Pounds 
per  ton. 

Velocity. 

Authority. 

Sand     

i 

448 

Pace 

Bevan 

& 

187 

3'  to  12'  per  sec. 

Morin 

? 

320 

Pace 

Bevan 

"      (4  in.  thick)  

A 

224 

Morin 

"      (common  road)  
"      (road)  

i 

140 

86 

« 
3  per  sec. 

Macheil 
Rumford 

«          t< 

3, 

90 

12'  per  sec. 

RESISTANCE   TO   TRACTION. 


373 


RESISTANCE  TO  TRACTION  ON  DIFFERENT  ROAD-SURFACES—  Contin ued. 


Character  of  Road. 

Resistance 
in  Terms  of 
Load. 

Pounds 
per  ton. 

Velocity. 

Authority. 

A 

75 

Pace 

j  Bevan 

Turf  (wet)  

| 

280 

« 

(  Minard 
Moiin 

"    (dry  and  hard)  

JL 

124 

tt 

2 

90 

Bevan 

Earth  (ordinary  road)  
Earth  (dry  and  hard)  .... 

^A 

224 
101-75 

Pace 
« 

Morin 

Clay  (hard)   

112 

Bevan 

Cobblestones  (ordinary).  .  . 

I 

280 

Trot 

(good,  Si  in'.).' 
Macadam  (little  usod)  

1, 

140 
150 
75 
140-97 

Pace 
Trot 
Pace 

'  Kossack* 
« 

Morin 

(bad). 

*r* 

160 

Pace 

Gordon 

'         fold) 

JL 

90 

Navier 

"        (ordinary)  .  .  .  •  . 

iff 

JL 

90 

Trot 

(  MacNeU 

it               11 

Macadam    (good,    slightly 
muddy)                «         • 

^ 

JL-JL 

64 

75-41 

Pace 

(  Perdon't 
Kossack 

Morin 

45 

Navier 

Macadam  (very  hard    and 
smooth) 

<a 

JL 

45 

MacNeil 

X 

64 

Trot 

Rumford 

«            « 

s 

50 

Pace 

n 

it            « 

jJLi 

48-37 

Gordon 

tt            tt 

5RJ 

52-30 

Morin 

Belgian  block  (ordinary).  .  . 
Bel   block  (Boulev    Paris) 

5. 

-1-1L 

56 
50-34 

Pace 

MacNeil 
Navier 

"          "      (aood) 

A 

75 

Trot 

Rumford 

1C                     ft                      tf 

s 

37 

Pace 

« 

"          "      (well  laid) 

2 

35 

MacNeU 

"             "       (frond} 

/fi 

50-26 

Morin 

4587 
1 

90 

(  Perdon't 
•<  Poncelet 

"         "      fffood") 

T7 

JL 

132 

Trot 

(  Minard 
Rumford 

«          «            « 

£ 

45 

Pace 

« 

tt           tt       frrnncl  Tjondl 

2 

36 

Gordon 

,wv 

56-40 

Morin 

A  onhalt 

40     57 
Ti« 

17 

Gordon 

14 

130     16« 

11 

« 

Sleighs  ou  snow  3  in.  thick 
£  in.  runner,  temperature 

2ft°  Fn.hr 

JL 

75 

TO 

320 

1 

51 

98 

.  S. 

38 

Dept. 

1             A   rr-vZ 

42 

Agn- 

54 

culture. 

Asphalt  (poor)  

26 

- 

374  HIGHWAY   CONSTRUCTION. 

tions  which  are  generally  rounded  off,  indicate  the  part  of  the  whole 
weight  which  is  equivalent  to  the  resistance  of  drawing  it  on  a 
level  road.  An  examination  of  this  table  will  clearly  show  the  great 
economy  in  horse-power  by  using  the  hardest  and  smoothest  ma- 
terial for  road-coverings.  For  instance,  if  1  horse  can  just  draw  a 
load  on  a  level  road  on  iron  rails,  it  will  require  1£  horses  to  draw  it 
on  asphalt,  3£  on  the  best  Belgian-block  pavement,  7  on  good 
cobblestone  pavement,  13  on  bed  cobblestone,  20  on  an  ordinary 
earth  road,  and  40  on  a  sandy  road. 

523.  The   following  deductions  are  from  the  experiments  of 
MM.  Dupuit  and  Morin: 

1st.  The  resistance  to  traction  on  uniform  smooth  surfaces  is 
directly  proportional  to  the  load,  and  inversely  as  the  square  root  of 
the  diameter  of  the  wheels. 

2d.  It  is  independent  of  the  width  of  the  tire  when  this  quantity 
exceeds  3  or  4  inches. 

3d.  It  is  independent  of  the  speed. 

4th.  On  paved  surfaces  which  give  rise  to  constant  concussion, 
it  increases  with  the  speed. 

5th.  Upon  soft  roads  of  earth  or  sand  or  turf,  or  roads  fresh 
and  thickly  gravelled,  the  resistance  to  traction  is  independent  of 
the  velocity. 

6th.  At  a  walking  pace,  the  resistance  is  the  same,  under  the 
same  circumstances,  for  vehicles  with  springs  and  for  vehicles  with- 
out springs. 

7th.  The  destruction  of  the  road  is,  in  all  cases,  greater  as  the 
diameter  of  the  wheels  is  less,  and  it  is  greater  in  vehicles  without 
than  with  springs. 

524.  The  comparative  ease  of  draft  on  various  surfaces  is  largely 
Influenced  by  the  amount  of  foothold  afforded,  and   it  may  be 
doubted  if  dynamometer  experiments,  however  carefully  made,  are 
altogether  conclusive.     The  tractive  force  is  influenced  by  the  di- 
ameter of  the  wheels,  the  friction  of  the  wheels  on  the  axles,  and  the 
speed,  as  well  as  by  the  resistance  of  the  road  surface;  and  these 
must  be  all  taken  into  account  to  obtain  accurate  results.     Kecent 
experiments  on  London  and  Paris  street  pavements  gave  the  fol- 
lowing results,  speed  2  to  6  miles  per  hour: 


RESISTANCE   TO   TRACTION". 


TABLE  LI. 
TRACTIVE  FORCE  ON  A  LEVEL. 


Surface. 

Pounds  per  ton. 

Londolr. 

Paris. 

Macadamized  .  .  .       

40.7    to  44.  29 
89.0     "39.32 
33.62  "36.03 
26.2    "27.00 

32.12  to  39.  38 

Asphalt       

Wood  

33.  44  to  39  16 
35.20 

'Granite            

525.  Gravity. — The  grade  of  the  road,  or  the  quantity  by  which 
it  differs  from  a  level.  The  grade  resistance  is  due  to  the  force  of 
gravity,  and  is  the  same  on  both  good  and  bad  roads,  and  unlike  the 
others  may  be  determined  from  the  laws  of  mechanics,  whilst  the 
former  are  determinable  entirely  by  experiment  on  the  road  in 
•question.  The  resistance  due  to  gravity  on  any  incline  in  pounds 

2240 

per  ton  =  —     — = •=-. 

rate  of  grade 


TABLE  LII. 
RESISTANCE  DUE  TO  GRAVITY  ON  DIFFERENT  INCLINATIONS. 


Grade  1  in  

90 

80 

40 

50 

60 

70 

80 

90 

100 

P,00 

300 

400 

Rise  in  feet  per  mile  

264 

176 

132 

105 

88 

75 

66 

58 

52 

26 

17 

13 

Resistance  in  Ibs.  per  ton 

112 

74| 

56 

45 

38 

32 

28 

25 

22 

1U 

7* 

5* 

526.  The  additional  resistance  caused  by  inclines  may  be  inves- 
tigated in  the  following  manner:  Suppose  the  whole  weight  to  be 
borne  on  one  pair  of  wheels,  and  that  the  tractive  force  is  applied 
in  a  direction  parallel  to  the  surface  of  the  road. 

Let  AB  in  Fig.  40  represent  a  portion  of  the  inclined  road,  C 
being  a  vehicle  just  sustained  in  its  position  by  a  force  acting  in  the 
direction  CD.  It  is  evident  that  the  vehicle  is  kept  in  its  position 
by  three  forces ;  namely,  by  its  own  weight  W  acting  in  the  vertical 
direction  CF,  by  the  force  F  applied  in  the  direction  CD  parallel 
to  the  surface  of  the  road,  and  by  the  pressure  P  which  the  vehicle 
exerts  against  the  surface  of  the  road  acting  in  the  direction  CE 
perpendicular  to  the  same.  To  determine  the  relative  magnitude 


376 


HIGHWAY    CONSTRUCTION. 


of  these  three  forces,  draw  the  horizontal  line  A  G  and  the  vertical 
one  B  G ;  then,  since  the  two  lines  CF  and  B  G  are  parallel  and  are 


FIG.  40. 

both  cut  by  the  line  AB,  they  must  make  the  two  angles  CFE  and 
AB G  equal;  also  the  two  angles  CEFand.  AGB  are  equal;  there- 
fore the  remaining  angles  FCE  and  BA  G  are  equal,  and  the  two- 
triangles  CFE  and  ABG  are  similar.  And  as  the  three  sides  of  the 
former  are  proportional  to  the  three  forces  by  which  the  vehicle  is 
sustained,  so  also  are  the  three  sides  of  the  latter;  namely,  AB  or 
the  length  of  the  road  is  proportional  to  W,  or  the  weight  of  the 
vehicle ;  B  G,  or  the  vertical  rise  in  the  same,  to  F,  or  the  force  re- 
quired to  sustain  the  vehicle  on  the  incline ;  and  A  G,  or  the  hori- 
zontal distance  in  which  the  rise  occurs,  to  P,  or  the  force  with 
which  the  vehicle  presses  upon  the  surface  of  the  road.  Therefore 


and 


W:AB::F:  GB, 


W:AB::P:AG. 


And  if  to  A  G  such  a  value  be  assigned  that  the  vertical  rise  of  the 
road  is  exactly  one  foot,  then 


W 


- 
AB 


:=z  =  W.  sin  A, 


RESISTANCE   TO   TRACTION.  377 

and 

„       W.AG         W.AG          _._ 

P    =    -7-p-     =    -~  =       W.   COS     Ay 

AB       VAGF  +  I 

in  which  A  is  the  angle  BA  G. 

527.  To  find  the  force  requisite  to  sustain  a  vehicle  upon  an 
inclined  road  (the  effects  of  friction  being  neglected),  divide  the 
weight  of  the  vehicle  and  its  load  by  the  inclined  length  of  the 
road,  the  vertical  rise  of  which  is  one  foot,  and  the  quotient  is  the 
force  required. 

528.  To  find  the  pressure  of  a  vehicle  against  the  surface  of  an 
inclined  road,  multiply  the  weight  of  the  loaded  vehicle  by  the  hori- 
zontal length  of  the  road,  and  divide  the  product  by  the  inclined 
length  of  the  same;  the  quotient  is  the  pressure  required. 

529.  The  force  with  which  a  vehicle  presses  upon  an  inclined 
road  is  always  less  than  its  actual  weight;  the  difference  is  so  small 
that,  unless  the  inclination  is  very  steep,  it  may  be  taken  equal  to 
the  weight  of  the  loaded  vehicle. 

530.  To  find  the  resistance  to  traction  in  passing  up  or  down  an 
incline,  ascertain  the  resistance  on  a  level  road  having  the  same 
surface  as  the  incline,  to  which  add,  if  the  vehicle  ascends,  or  sub- 
tract, if  it  descends,  the  force  requisite  to  sustain  it  on  the  incline; 
the  sum  or  difference,  as  the  case  may  be,  will  express  the  resistance. 

531.  Tractive  Power  and  Gradients. — The  necessity  for  easy 
grades  is  dependent  upon  the  power  of  the  horse  to  overcome  the 
resistance  to  motion  composed  of  the  four  forces,  friction,  collision, 
gravity,  and  the  resistance  of  the  air. 

All  estimates  on  the  tractive  power  of  horses  must  to  a  certain 
extent  be  vague,  owing  to  the  different  strengths  and  speeds  of 
animals  of  the  same  kind,  as  well  as  to  the  extent  of  their  training 
to  any  particular  kind  of  work.  Authorities  on  the  subject  differ 
widely,  and  sometimes  express  themselves  in  a  loose  manner  that 
throws  doubt  on  their  meaning. 

532.  The  draught  or  pull  which  a  good  average  horse,  weighing 
1200  pounds,  can  exert  on  a  level,  smooth  road  at  a  speed  of  2£ 
miles  per  hour  is  100  pounds,  equivalent  to  22,000  foot-pounds  per 
minute,  or  13,200,000  foot-pounds  per  day  of  10  hours. 

533.  The  tractive  power  diminishes  as  the  speed  increases  and 
perhaps,  within  certain  limits,  say  from  f  to  4  miles  per  hour,  nearly 


378 


HIGHWAY    CONSTRUCTION-. 


in  inverse  proportion  to  it.  Thus  the  average  tractive  force  of  a 
horse,  on  a  level,  and  actually  pulling  for  10  hours,  may  be  assumed 
approximately  as  follows: 

TABLE  LIII. 
TRACTIVE  POWER  OP  HORSES  AT  DIFFERENT  VELOCITIES. 


Miles  per  hour. 

Tractive  Force. 
Pounds. 

Miles  per  hour. 

Tractive  Force. 
Pounds. 

A 

333  33 

2i.. 

111.11 

1 

250 

2* 

100 

200 

2* 

90.91 

li 

166  66 

3  

83.33 

1* 

142.86 

3|  

71.43 

i*  

125 

4       

62.50 

534.  The  work  done  by  a  horse  is  greatest  when  the  velocity 
with  which  he  moves  is  -£  of  the  greatest  velocity  with  which  he  can 
move  when  unloaded;  and  the  force  thus  exerted  is  0.45  of  the 
utmost  force  that  he  can  exert  at  a  dead  pull. 

TABLE  LIV. 
DURATION  OF  A  HORSE'S  DAILY  LABOR  AND  MAXIMUM  VELOCITY  UNLOADED. 


Duration  of  Labor. 
Hours. 

Maximum  Velocity. 
Miles  per  hour. 

Duration  of  Labor. 
Hours. 

Maximum  Velocity. 
Miles  per  hour. 

1        

14.7 

6  

6  0 

2     

10.4 

7  ,  

5.5 

3  

8.5 

8  

5.2 

4     

7.3 

9  t.. 

4.9 

5  

6.6 

10  

4.6 

535.  The  tractive  power  of  a  horse  may  be  increased  in  about 
the  same  proportion  as  the  time  is  diminished,  so  that  when  working 
from  5  to  10  hours,  on  a  level,  it  will  be  about  as  shown  in  the  fol- 
lowing table : 

TABLE  LV. 


Hours  per  day. 

Traction  (pounds). 

Hours  per  day. 

Traction  (pounds). 

10     

100 

7  

146£ 

9  

HH 

6  

1661 

8     . 

125 

5     

200  " 

RESISTANCE   TO   TRACTION". 


379 


The  tractive  power  of  teams  is  about  as  follows : 


1  horse =1 

2  horses 0.95  x  2  =  1.90 

3  "      0.85X3  =  2.55 

4  "  0.80  x  4  =  3.20 


Table  LVI  is  useful  as  showing  the  maximum  amount  of  labor 
a  horse  of  average  strength  is  capable  of  performing  at  different 
Tates  of  speed. 

TABLE  LVI. 


Resistance  to 

Useful  Effect  of  One  Horse  working  1 
day  in  tons  drawn  1  mile.* 

Speed  in 

Duration  of  the 

Traction 

Miles  per  hour. 

Day's  Work. 

assumed  at 

On  Level  Iron  Rails. 

On  Level  Maca- 

Pounds. 

Tons. 

dam.    Tons. 

2* 

1H 

83* 

115 

14 

3 

8 

83* 

92 

12 

3* 

§JL 

83* 

82 

10 

4 

S3* 

72 

9 

5 

83* 

57 

7.2 

6 

2™ 

83* 

48 

6.0 

7 

H 

83* 

41 

5.1 

8 

H 

83* 

36 

4.5 

9 

A 

83* 

32 

4.0 

10 

83* 

28.8 

3.6 

*  The  actual  labor  which  a  horse  can  perform  is  greater,  but  he  is  injured 
by  it 

536.  Loss  of  Tractive  Power  on  Inclines. — In  ascending  inclines 
a  horse's  power  diminishes  rapidly;  a  large  portion  of  his  strength 
is  expended  in  overcoming  the  resistance  of  gravity  due  to  his  own 
weight  and  that  of  the  load.  Table  LVIII  shows  that  as  the  steep- 
ness of  the  grade  increases  the  efficiency  of  both  the  horse  and  the 
road-surface  diminishes;  that  the  more  the  horse's  energy  is  ex- 
pended in  overcoming  gravity  the  less  remains  to  overcome  the 
surface-resistance. 

Table  LVII  shows  the  gross  load  which  an  average  horse, 
weighing  1200  pounds,  can  draw  on  different  kinds  of  road-surfaces, 
<m  a  level  and  on  grades  rising  five  and  ten  feet  per  one  hundred 
feet. 


380 


HIGHWAY   CONSTKUCTION. 


TABLE  LVII. 


Description  of  Surface. 

Level. 

5  per  cent. 
Grade. 

10  per  cent. 
Grade. 

Pounds. 
13216 

Pounds. 

Pounds. 

Broken  stone  (best  condition)  
«•          "      (slightly  muddy)  

6,700 
4700 

1,840 
1,500 

1,060 
1,000 

3000 

1,390 

890 

"          "     (very  bad  condition) 

1  840 

1  040 

740 

Earth  (best  condition)                    

3  600 

1,500 

930 

"      (average  condition)       

1  400 

900 

660 

'  *      (moist  but  not  muddy) 

1  100 

780 

600 

Stone-block  pavement  (dry  and  clean). 
"         "             "         (muddv).. 

8,300 
6  250 

1,920 
1,800 

1,090 
1,040 

Sand  (wet)  

1,500 

675 

390 

••'     (dry)  

1,087 

445 

217 

The  formula  which  shows  the  relation  of  the  tractive  force  to 
the  weight  of  the  load  is 

K  =  pQ+(G+Q)  tan  a, 

in  which  K  represents  the  mean  tractive  power  of  the  horse,  taken 
at  \  of  its  weight,  equal  to  165  of  its  weight,  equal  to- 
165  pounds; 

/f  the  coefficient  of  resistance  to  traction; 
Q  the  load,  including  the  weight  of  the  wagon; 
G  the  mean  weight  of  the  horse  =  165  X  5  =  825  pounds; 
a  the  angle  of  inclination. 
Q,  the  load  in  the  above  expression,  is  equal  to 

K—  G  tana 
, 

}JL  -f-  tan  a 

and  this  form  has  been  utilized  for  the  computation  of  Table  LVIIfl,. 
showing  the  load  (with  vehicle)  that  the  average  horse,  exerting  an 
average  tractive  force,  can  pull  up  a  continuous  incline  having 
various  grades  and  different  coefficients  of  resistance,  without  re- 
quiring reinforcement  at  any  time. 

While  the  above  formula  holds  good  for  all  inclinations  shown 
in  the  table,  it  must  be  stated  that  it  is  no  longer  applicable  for  ex- 
cessive grades,  for  the  tractive  force  in  reality  diminishes  so  rapidly 
that  at  an  angle  of  30  degrees  it  becomes  zero. 


RESISTANCE    TO   TRACTION. 


381 


TABLE   LVIIa. 


Values  M 

|      '-  • 

Values  ft 

Grade 
tan  a 

A 

A 

A 

A 

i 

Grade 
tan  a 

A 

& 

A       A 

i 

Load  Q  in  Pounds. 

Load  Q  in  Pounds. 

0.000 

8250 

4950 

3300 

1650 

825 

0.022 

3497 

2654 

2040 

1204 

661 

0.002 

7425 

4627 

3141 

1601 

808 

0.025 

8*8 

2476 

1925 

1155 

642 

0.004 

6737 

4335 

2994 

1555 

793 

0.028 

2956 

2315 

1819 

1109 

623 

0.008 

5657 

3835 

2731 

1467 

761 

0.033 

2599 

2078 

1660 

1036 

591 

0.010 

5225 

3620 

2612 

1425 

747 

0.040 

2200 

1800 

1467 

943 

550 

0.012 

4847 

3424 

2502 

1385 

732 

0.050 

1764 

1483 

1238 

825 

495 

0.016 

4217 

3079 

2300 

1309 

703 

0.066 

1285 

1113 

953 

666 

415 

0.020 

3713 

2786 

2121 

1237 

615 

0.100 

687 

610 

550 

413 

275 

537.  The  decrease  in  the  load  which  a  horse  can  draw  upon  an 
incline  is  not  due  alone  to  gravity;  it  varies  with  the  amount  of 
foothold  afforded  by  the  road-surface.  The  tangent  of  the  angle  of 
inclination  should  not  be  greater  than  the  coefficient  of  tractional 
resistance;  therefore  it  is  evident  that  the  smoother  the  road-sur- 
face the  easier  should  be  the  grade.  The  smoother  the  surface  the 
less  the  foothold,  and  consequently  the  load.  Table  LVIII  shows 
the  decrease  in  the  loads  caused  by  various  road-coverings  on  grades 
from  1  to  20  per  cent. 

TABLE  LVIII. 

EFFECT  OF  GRADES  UPON  THE  LOADS  A  HORSE  CAN  DRAW  ON  DIFFERENT 

PAVEMENTS. 


Grade. 

Earth. 

Broken  Stone. 

Stone  Blocks. 

Asphalt. 

Level  

1.00 

1.00 

1.00 

1.00 

1  •  100        

.80 

.66 

.72 

.41 

2  .  100  

.66 

.50 

.55 

.25 

3  •  100  

.55 

.40 

.44 

.18 

4  •  100           

.47 

.33 

.36 

.13 

5  •  1  00     

.41 

.29 

.30 

.10 

10  •  100  

.26 

.16 

.14 

.04 

15  •  100             

.10 

.05 

.07 

•20  •  100  

.04 

.03 

.... 

538.  The  loss  of  tractive  power  on  inclines  is  greater  than  any 
investigation  will  show;  for,  besides  the  increase  of  draught  caused 
by  gravity,  the  power  of  the  horse  is  much  diminished  by  fatigue 


382  HIGHWAY    CONSTRUCTION. 

upon  a  long  ascent,  and  even  in  greater  ratio  than  man,  owing  to  its 
anatomical  formation  and  great  weight.  Though  a  horse  on  a  level 
is  as  strong  as  five  men,  on  a  grade  of  15  per  cent,  it  is  less  strong 
than  three;  for  three  men  carrying  each  100  pounds  will  ascend 
such  a  grade  faster  and  with  less  fatigue  than  a  horse  with  30O 
pounds. 

539.  A  horse  can  exert  for  a  short  time  twice  the  average  trac- 
tive pull  which  he  can  exert  continuously  throughout  a  day's  work; 
hence,  so  long  as  the  resistance  on  the  incline  is  not  more  than 
double  the  resistance  on  the  level,  the  horse  will  be  able  to  take  up 
the  full  load  which  he  is  capable  of  drawing. 

540.  Steep  grades  are  thus  seen  to  be  objectionable,  and  partic- 
ularly so  when  a  single  one  occurs  on  an  -otherwise  comparatively 
level  road,  in  which  case  the  load  carried  over  the  less  inclined  por- 
tions must  be  reduced  to  what  can  be  hauled  up  the  steeper  portion. 

541.  The  bad  effects  of  steep  grades  are  especially  felt  in  winter,, 
when  ice  covers  the  roads,  for  the  slippery  condition  of  the  surface 
causes  danger  in  descending,  as  well  as  increased  labor  in  ascending; 
the  water  of  rains  also  runs  down  the  road  and  gulleys  it  out, 
destroying  its  surface,  thus  causing  a  constant  expense  for  repairs. 
The  inclined  portions  are  subjected  to  greater  wear  from  the  feet 
of  horses  ascending,  thus  requiring  thicker  covering  than  the  more 
level  portions,  and  hence  increasing  the  cost  of  construction. 

542.  It  will  rarely  be  possible,  except  in  a  flat  or  comparatively 
level  country,  to  combine  easy  grades  with  the  shortest  and  most 
direct  route.    These  two  requirements  will  often  conflict;  in  such  a 
case  increase  the  length.     The  proportion  of  this  increase   will 
depend  upon  the  friction  of  the  covering  adopted.     But  no  general 
rule  can  be  given  to  meet  all  cases  as  respects  the  length  which  may 
thus  be  added,  for  the  comparative  time  occupied  in  making  the 
journey  forms  an  important  element  in  any  case  which  arises  for 
settlement.   Disregarding  time,  the  horizontal  length  of  a  road  may- 
be increased,  to  avoid  a  5  per  cent  grade,  seventy  times  the  height. 

Table  LIX  shows  with  sufficient  exactness  for  most  practical 
purposes  the  force  required  to  draw  loaded  vehicles  over  inclined 
roads.  The  first  column  expresses  the  rate  of  inclination ;  the  second, 
the  pressure  on  the  plane  in  pounds  per  ton ;  the  third,  the  tendency 
down  the  plane  (or  force  required  to  overcome  the  effect  of  gravity) 
in  pounds  per  ton;  the  fourth,  the  force  required  to  haul  one  ton  up 


RESISTANCE   TO   TRACTION. 


383 


TABLE  LIX. 


Rate 
of  Grade. 
Feet  per 
100  feet. 

i    Pressure  on 
the  Plane  in 
Ibs.  per  ton. 

Tendency 
down  the 
Plane  in  Ibs. 
per  ton. 

i 

Power  in  Ibs. 
required  to 
haul  one  ton 
up  the  Plane. 

!     Equivalent 
Length  of 
Level  Road. 
Miles. 

Maximum 
Load  in  Ibs. 
which  a  Horse 
can  haul. 

0.0 

2240 

00 

45.00 

1.000 

6270 

0.25 

5.60 

50.60 

1.121 

5376 

0.50 

11.20 

56.20 

1.242 

4973 

0.75 

16.80 

61.80 

1.873 

4490 

1 

* 

22.40 

67.40 

1.500 

4145 

1.25 

28.00 

73.00 

1.622 

3830 

1.50 

33.60 

78.60 

1.746 

3584 

1.75 

39.20 

84.20 

1.871 

3290 

2 

45.00 

90.00 

2.000 

3114 

2.25 

50.40 

95.40 

2.120 

2935 

2.50 

56.00 

101.00 

2.244 

2725 

2.75 

61.33 

106.33 

2.363 

2620 

3 

2239 

67.20 

112.20 

2.484 

2486 

4 

2238 

89.20 

134.20 

2  982 

2083 

5 

2237 

112.00 

157.00 

3.444 

1800 

6 

2233 

134.40 

179.40 

3.986 

1568 

7 

2232 

156.80 

201.80 

4.844 

1367 

8 

» 

179.20 

224.20 

4.982 

1235 

9 

2231 

201.60 

246.60 

5.480 

1125 

10 

2229 

224.00 

269.00 

5.977 

1030 

*  Near  enough  for  practice,  actually  2239.888. 

Pressure  on  the  plane  —  weight  X  nat  cos  of  angle  of.  plane. 

the  incline;  the  fifth,  the  length  of  level  road  which  would  be 
equivalent  to  a  mile  in  length  of  the  inclined  road — that  is,  the 
length  which  would  require  the  same  motive  power  to  be  expended 
in  drawing  the  load  over  it  as  would  be  necessary  to  draw  it  over  a 
mile  of  the  inclined  road;  the  sixth,  the  maximum  load  which  an 
average  horse  weighing  1200  pounds  can  draw  over  such  inclines, 
the  friction  of  the  surface  being  taken  at  -fa  of  the  load  drawn. 

543.  Character  of  Vehicles. — The  character  of  the  vehicles  used 
upon  a  roadway  has  a  great  influence  upon  its  endurance  to  the 
beat  of  the  wheels.  The  great  defect  of  our  vehicles  is  that  for  a 
given  load  the  tires  of  the  wheels  are  too  narrow.  It  has  been 
proved  by  repeated  and  careful  experiments  that  wheels  with  tires 
two  and  a  half  inches  wide  cause  double  the  wear  of  wheels  which 
have  tires  four  and  a  half  inches  wide.  It  is  true  that  on  ill-con- 
ditioned and  muddy  roads  a  narrow  wheel-tread  is  advantageous, 
for  the  reason  that  the  thick  mud  has  a  less  extended  hold  when  it 
wraps  around  the  felloes  and  spokes;  but  with  this  arrangement 


384 


HIGHWAY    CONSTRUCTION. 


the  interests  of  the  roadway  are  sacrificed  to  the  convenience  of  the 
individual  who  drives  upon  it. 

544.  The  width  of  the  surface  covered  by  these  narrow  tires  is 
not  sufficient  to  bear  the  heavy  load  imposed  upon  it,  and  the  knife- 
like  tire  cuts   into  it,  forming  and  deepening  ruts.     The  proper 
width  of  tire,  or  proper  load  upon  any  vehicle  for  a  given  width  of 
tire,  is   a  question  that   deserves  more   attention  than  is  usually 
accorded  to  it. 

545.  The  best  width  of  tire  measured  when  new  is  shown  in 
Table  LX. 

These  widths  are  best  for  easy  traction  and  the  maximum  wear 
of  the  road-surface.  To  make  the  tires  wider  does  not  diminish  the 
force  required  to  move  the  load,  and  unnecessarily  increases  the 
dead  weight  of  the  vehicles.  For  carriages,  coupes,  and  vehicles 
for  light  passenger  use  the  tires  need  not  exceed  %%  inches  and 
should  never  be  less  than  2  inches. 

The  width  of  tires  should  be  established  by  law. 

The  French  Commission,  presided  over  by  Morin  and  Dnpnit, 
recommends  as  maximum  width  of  tire  4f  inches,  and  as  minimum 
width  2f  inches. 

The  best  European  practice  allows  only  from  500  to  900  pounds 
per  inch  width  of  tire.  In  the  United  States  loads  ranging  from 
1000  to  5000  pounds  per  inch  width  of  tire  are  quite  common. 

TABLE  LX. 


Description  of  Vehicles. 


Load  on  each 
Wheel. 

Two  Wheels 
without  Springs. 
Inches. 

Two  Wheels 
with  Springs. 
Inches. 

Four  Wheels 
without  Springs. 
Inches. 

Four  Wheels 
with  Springs. 
Inches. 

t  ton 

i    " 

1    " 

6 
6 

3 
8 

5 
5 
5 

3 
3 

31 

11  " 

5 

4 

2    " 

6 

4| 

546.  The  freight  and  market  wagons  of  France  have  tires  from 
3  to  10  inches  in  width,  usually  from  4  to  6  inches.     The  four- 


NOTE. — All  laws  regarding  the  width  of  tires  in  London  have  been  abol- 
ished. 


RESISTANCE   TO   TRACTION".  385 

wheeled  freight-wagons  have  tires  rarely  less  than  6  inches  and  the 
rear  axle  is  about  14  inches  longer  than  the  fore,  so  that  the  rear 
wheels  run  on  a  line  about  an  inch  outside  of  the  line  of  the  fore- 
wheels.  The  varied  gauge  is  also  usually  observed  with  cabs,  hacks, 
and  other  four-wheeled  vehicles. 

547.  In  Bavaria  the  width  of  the  wheel-tires  is  laid  down  by  law 
as  follows : 

2-wheeled  carts  with  2  horses 4.133  inches 

"    4      "     6.180      " 

4-wheeled  carts  with  2     " 2.596      " 

"  "        "    3  or  4  horses 4.133 

"    5to8      "    6.180      " 

Carts  with  more  than  four  and  wagons  with  more  than  eight 
horses  are  not  allowed  to  use  the  road  except  under  special  permit 
from  the  authorities. 

548.  In  Austria  the  width  of  tires  for  wagons  carrying  2£  tons 
tons  is  4.33  inches,  and  for  wagons  carrying  4J-  tons  6.30  inches. 

548a.  In  June,  1892,  the  Studebaker  Bros.  Mfg.  Co.  of  South 
Bend,Ind.,  made  a  series  of  tests  to  determine  the  relative  merits  of 
wide  and  narrow  tires  with  regard  to  the  resistance  they  offered  to 
traction  upon  different  road-surfaces.  The  wagon  employed  was  a 
regular  3|-inch  thimble-skein  wagon  having  in  one  set  of  tests 
wheels  3  feet  8  inches  and  4  feet  6  inches  in  diameter,  and  in 
another  set  3  feet  6  inches  and  3  feet  10  inches.  A  Fairbanks 
dynamometer  was  attached  to  the  double-tree,  and  the  team  exerted 
their  pull  through  the  instrument  to  move  the  load. 

The  tests  showed  that  the  width  of  tire  has  very  little  effect  upon 
the  power  required  to  move  loads  upon  hard  surfaces,  such  as  stone 
blocks,  hard  sand,  or  gravel,  the  power  required  to  move  a  load 
of  one  ton  (2240  pounds)  being  on 

Stone  blocks  with  1^-in.  tire  168  pounds;  with  4-in.  tire  180 pounds. 
Hard  sand         "      "    "      "     383       "          "     "  "     "    360       " 
Hard  gravel      "     "   "     "    344       "          "    "  "     "    311       " 

Upon  soft  ground,  such  as  mud  and  grass  sods,  into  which  the 
narrow  tires  would  cut,  the  wide  tires  have  a  slight  advantage,  the 
power  required  to  move  one  ton  (2240  pounds)  being  on 
Soft  rnud  with  H-in.  tire  476  pounds;  with  4-in.  tire  412  pounds. 
Sod  "     "   "      "    610        "  "      3   "      "    537        " 

The  power  required  to  keep  the  load  in  motion  after  being 
started  was  found  to  range  from  25  to  50  per  cent  less  than 


386  HIGHWAY    CONSTRUCTION. 

that  required  to  start  it.  It  was  also  found  that  less  power  was 
required  to  start  the  load  when  wheels  of  large  diameter  were  em- 
ployed, and  that  the  diameter  of  the  wheel  had  no  apparent  effect 
on  the  power  required  to  keep  the  load  in  motion. 

Numerous  tests  of  the  influence  of  width  of  tire  on  draft  of 
wagons  have  been  made  at  the  University  of  Missouri.  The  fol- 
Jowing  is  a  brief  summary  of  the  results : 

The  width  of  the  tires  used  was  one  and  one-half  inches  and  six 
inches.  The  draft  was  determined  by  a  self-recording  dynamometer. 
The  net  load  in  every  trial  was  2000  pounds. 

The  loads  which  could  be  hauled  with  the  same  draft  were  on: 

1^-inchTire.  6-inch  Tire.    . 

Macadam 2000  Ibs.  2518  Ibs. 

Gravel,  good  condition 2000    "  2482   " 

Dirt,  dry  and  hard 2000   "  2500   " 

Clay,  with  mud,  deep  and  drying  on  top 

and  spongy  underneath  (1) 2000    "  3200   " 

(1)  In  this  condition  of  road  the  broad  tires  show  to  their  great- 
est advantage.  As  the  road  dries  and  becomes  firmer  the  difference 
between  the  draft  of  the  broad  and  the  narrow  tires  gradually  dimin- 
ishes until  it  reaches  about  25  to  30  per  cent  on  dry,  hard,  smooth 
dirt,  gravel,  or  macadam,  in  favor  of  the  broad  tire.  On  the  other 
hand,  as  the  mud  becomes  softer  and  deeper,  the  difference  between 
the  draft  of  the  two  types  of  tires  rapidly  diminishes  until  the  con- 
dition is  reached  when  the  mud  adheres  to  both  styles  of  wheels. 
Here  the  advantage  of  the  broad  tires  ceases  entirely,  and  the  draft 
required  for  the  narrow  tires  is  considerably  less. 

Clay,  surface  dry,  with  deep  ruts  cut  by  narrow  tires  in  the 
ordinary  use  of  the  road.  The  first  run  of  the  broad  tire  over  the 
narrow-tire  rut  showed  a  materially  increased  draft  when  compared 
with  that  of  the  narrow  tire  run  in  its  own  rut.  The  second  run 
of  the  broad  tire  in  the  same  track  where  the  rut  was  not  deep 
completely  eliminated  this  disadvantage,  and  showed  a  lighter 
draft  for  the  broad  tire  than  the  narrow  tire  showed  in  the  first 
run.  When  the  ruts  were  eight  inches  deep  with  rigid  walls  three 
runs  of  the  broad  tire  in  its  own  track  over  the  ruts  were  required 
to  eliminate  the  disadvantage. 


RESISTANCE    TO    TRACTION".  387 

The  conditions  which  showed  results  unfavorable  to  the  broad 
tires  were  : 

Gravel,  wet  and  sloppy. 

Dirt. — 1.  When  sloppy,  muddy,  or  sticky  on  the  surface  and 
firm  or  hard  underneath. 

2.  When  covered  with  a  very  deep,  loose  dust  and  hard  under- 
neath. 

3.  When  the  mud  is  very  deep  and  so  sticky  that  it  adheres  to 
the  wheels  of  both  types. 

The  experimenters  concluded  that  the  best  width  of  tire  for  a 
combination  farm  and  road  wagon  is  six  inches,  and  that  both 
axles  should  be  the  same  length,  so  that  the  front  and  hind  wheels 
will  run  in  the  same  track. 

549.  Size  of  Wheels. — The  wheels  of  a  vehicle  serve  a  twofold 
purpose.     In  the  first  place,  they  dimmish  the  friction  on  the 
ground  by  transferring  it  from  the  circumference  to  the  nave  and 
axle;  and  in  the  second  place,  they  serve  to  raise  the  vehicle  more 
easily  over  obstacles  met  with  on  roads. 

550.  The  friction  is  diminished  in  the  proportion  of  the  circum- 
ference of  the  axle  to  that  of  the  wheel ;  and  hence  the  larger  the 
wheel  and  the  smaller  the  axle  the  less  is  the  friction. 

The  mechanical  advantage  of  the  wheel  in  surmounting  an 
obstacle  may  be  computed  from  the  principle  of  the  lever. 

Let  the  wheel,  Fig.  41,  touch  the  horizontal  line  of  traction  in  the 
point  A  and  meet  a  protuberance  BD.  Suppose  the  line  of  draught 


A     B 
FIG.  41. 

CP  to  be  parallel  to  AB.  Join  CD  and  draw  the  perpendiculars 
DE  and  DF.  We  may  suppose  the  power  to  be  applied  at  E  and 
the  weight  at  F,  and  the  action  is  then  the  same  as  the  bent  lever 
EDF turning  round  the  fulcrum  at  D.  Hence  P  :  W  : :  FD 


388  HIGHWAY   CONSTRUCTION". 

but  FD  :  DE  ::  tan  FCD  :  1,  and  tan  FCD  =  tan 
therefore  P  —  W  tan  %(DAB).  Now  it  is  obvious  that  the 
angle  DAB  increases  as  the  radius  of  the  circle  diminishes;  and 
therefore,  the  weight  W  being  constant,  the  power  required  to 
overcome  an  obstacle  of  a  given  height  is  diminished  when  the 
diameter  is  increased.  Large  wheels  are  therefore  the  best  adapted 
for  surmounting  inequalities  of  the  road. 

551.  There  are,  however,  circumstances  which  provide  limits  to 
the  height  of  the  wheels  of  vehicles.     If  the  radius  A  C  exceeds  the 
height  of  that  part  of  the  horse  to  which  the  traces  are  attached, 
the  line  of  traction  CP  will  be  inclined  to  the  horse,  and  part  of 
the  power  will  be  exerted  in  pressing  the  wheel  against  the  ground. 
The  best  average  size  of  wheels  is  considered  to  be  about  6  feet  in 
diameter. 

552.  Wheels  of  large  diameter  do  less  damage  to  a  road  than 
small  ones,  and  cause  less  draught  for  the  horses. 

553.  With  the  same  load  a  two-wheeled  cart  does  far  more 
damage  than  one  with  four  wheels,  and  this  because  of  their  sud- 
den and  irregular  twisting  motion  in  the  trackway. 

554.  Springs  materially  decrease  the  resistance   and  act   pre- 
servingly  on  both  road  and  vehicle. 

554a.  Umpfenbach  recommends  the  following  wheel  diameters 
for  vehicles  frequenting  good  roads  : 

1.  For   two-wheeled   freight-carts,  5  feet  3  inches  to  5  feet  9 
inches. 

2.  For  four-wheeled  freight-wagons,  front  wheels  3  feet  1  inch, 
hind  wheels  3  feet  9  inches  to  4  feet  2  inches. 

These  diameters  should  be  increased  from  6  to  12  inches  for 
traffic  on  bad  roads. 


CHAPTER  XL 
LOCATION  OF  COUNTRY  ROADS. 

555.  THE  considerations  governing  the  location  of  country  roads 
are  dependent  upon  the  commercial  condition  of  the  country  to  be 
traversed.     In  old  and  long-inhabited  sections  the  controlling  ele- 
ment will  be  the  character  of  the  traffic  to  be  accommodated.     In 
such  a  section  the  route  is  generally  predetermined,  and  therefore 
there  is  less  liberty  of  a  choice  and  selection  than  in  a  new  and 
sparsely  settled  district,  where  the  object  is  to  establish  the  easiest, 
shortest,  and  most  economical  line  of  intercommunication  accord- 
ing to  the  physical  character  of  the  ground. 

556.  Whichever  of  these  two  cases  may  have  to  be  dealt  with, 
the  same  principle  governs  the  engineer,  namely,  to  so  lay  out  the 
road  as  to  effect  the  conveyance  of  the  traffic  with  the  least  ex- 
penditure of  motive  power  consistent  with  economy  of -construction 
and  maintenance. 

557.  Economy  of  motive  power  is  promoted  by  easy  grades,  by 
the  avoidance  of  all  unnecessary  ascents  and  descents,  and  by  a 
direct  line;  but  directness  must  be  sacrificed  to  secure  easy  grades 
and  to  avoid  expensive  construction. 

558.  Reconnoissance. — The  selection  of  the  best  route  demands 
much  care  and  consideration  on  the  part  of  the  engineer.     To 
obtain  the  requisite  data  upon  which  to  form  his  judgment  he 
must  make  a  personal  reconnoissance  of  the  district.    This  requires 
that  the  proposed  route  be  either  ridden  or  walked  over  and  a 
careful  examination  made  of  the  principal  physical  contours  and 
natural  features  of  the  district.     The  amount  of  care  demanded 
and  the  difficulties  attending  the  operations  will  altogether  depend 
upon  the  character  of  the  country. 

559.  The  immediate  object  of  the  reconnoissance  is  to  select 
one  or  more  trial  lines,  from  which  the  final  route  may  be  ultimate- 
ly determined. 


390  HIGHWAY   CONSTRUCTION. 

When  there  are  no  maps  of  the  section  traversed,  or  when  those 
which  can  be  procured  are  indefinite  or  inaccurate,  the  work  of 
reconnoitring  will  be  much  increased. 

560.  In  making  a  reconnoissance  there  are  several  points  which, 
if  carefully  attended  to,  will  very  considerably  lessen  the  labor  and 
time  otherwise  required.    Lines  which  would  run  along  the  imme- 
diate bank  of  a  large  stream  must  of  necessity  intersect  all  the 
tributaries  confluent  on  that  bank,  thereby  demanding   a  corre- 
sponding number  of  bridges.  Those,  again,  which  are  situated  along 
the  slopes  of  hills  are  more  liable  in  rainy  weather  to  suffer  from 
washing  away  of  the  earthwork  and  sliding  of  the  embankments; 
the  others  whicji  are  placed  in  valleys  or  elevated  plateaux,  when 
the  line  crosses  the  ridges  dividing  the  principal  water-courses  will 
have  steep  ascents  and  descents. 

561.  In  making  an  examination  of  a  tract  of  country,  the  first 
point  to  attract  notice  is  the  unevenness  or  undulations  of  its  sur- 
face, which  appears  to  be  entirely  without  system,  order,  or  arrange- 
ment; but  upon  closer  examination  it  will  be  perceived  that  one 
general  principle  of  configuration  obtains  even  in  the  most  irregular 
countries.     The  country  is  intersected  in  various  directions  by  main 
water-courses  or  rivers,  which  increase  in  size  as  they  approach  the 
point  of  their  discharge.    Towards  these  main  rivers  lesser  rivers  ap- 
proach on  both  sides,  running  right  and  left  through  the  country, 
and  into  these,  again,  enter  still  smaller  streams  and  brooks.     The 
streams  thus  divide  the  hills  into  branches  or  spurs  having  approx- 
imately the  same  direction  as  themselves,  and  the  ground  falls  in 
every  direction  from  the  main  chain  of  hills  towards  the  water- 
courses, forming  ridges  more  or  less  elevated. 

562.  The  main  ridge  is  cut  down  at  the  heads  of  the  streams 
into  depressions  called  gaps  or  passes;  the  more  elevated  points  are 
called  peaks.     The  water  which  has  fallen  upon  these  peaks  is  the 
origin  of  the  streams  which  have  hollowed  out  the  valleys.  Further- 
more, the  ground  falls  in  every  direction  towards  the  natural  water- 
courses, forming  ridges  more  or  less  elevated  running  between  them 
and  separating  from  each  other  the  districts  drained  by  the  streams. 

563.  The  natural  water-courses  mark  not  only  the  lowest  lines, 
but  the  lines   of    the    greatest   longitudinal  slope  in  the  valleys 
through  which  they  flow. 

564.  The  direction  and  position  of  the  principal  streams  give 


LOCATION    OF    COUNTRY    ROADS.  391 

also  the  direction  and  approximate  position  of  the  high  ground  or 
ridges  which  lie  between  them. 

565.  The  position  of  the  tributaries  to  the  larger  stream  gener- 
ally indicates  the  points  of  greatest  depression  in  the  summits  of 
the  ridges,  and  therefore  the  points  at  which  lateral  communication 
across  the  high  ground  separating  contiguous  valleys  can  be  most 
readily  made. 

566.  The  instruments  employed    in  reconnoitring,  are: — The 
compass,  for  ascertaining  the  direction ;  the  aneroid  barometer,  to 
fix  the  approximate  elevation  of  summits,  etc. ;  and  the  hand-level, 
to  ascertain  the  elevation  of  neighboring  points.   If  a  vehicle  can  be 
used,  an  odometer  may  be  added,  but  distances  can  usually  be 
guessed  or  ascertained    by   time   estimates    or  otherwise,   closely 
enough  for  preliminary  purposes.     More  outfit  than  the  above  (the 
use  of  which  is  supposed  to  be  understood),  with  the  best  maps  ob- 
tainable and  a  succession  of  travelling  companions  who  possess  a 
local  knowledge  of  the  country,  will  not  be  particularly  useful. 

567.  The  reconnoissance  being  completed,  instrumental  surveys 
of  the  routes  deemed  most  advantageous  should  be  made.     When 
the  several  lines  are  plotted  to  the  same  scale,  a  good  map  can  be 
prepared  from  which  the  exact  location  of  the  road  can  be  deter- 
mined. 

568.  In  making  the  preliminary    surveys   the    topographical 
features  should  be  noted  for  a  convenient  distance  to  the  right 
and  left  of  the  line,  and  all  prominent  points  located  by  compass- 
bearings.     The  following  data  should  be  also  obtained :  the  impor- 
tance, magnitude,  and  direction  of  all  streams  and  roads  crossed ; 
the  character  of  the  material  to  be  excavated  or  available  for  em- 
bankments, the  position  of  quarries  and  gravel-pits,  and  the  modes 
of  access  thereto;  and  all  other  information  that  may  effect  a  selec- 
tion. 

569.  Topography.— There  are  various  methods  of  delineating 
upon  paper  the  irregularities  of  the  surface  of  the  ground.     The 
method  of  most  utility  to  the  engineer  is  that  by  means  of  "contour 
lines."   These  are  fine  lines  traced  through  the  points  of  equal  level 
over  the  surface  surveyed,  and  denote  that  the  level  of  the  ground 
throughout  the  whole  of  their  course  is  identical;  that  is  to  say,  that 
every  part  of  the  ground  over  which  the  line  passes  is  at  a  certain 


392  HIGHWAY    CONSTRUCTION. 

height  above  a  known  fixed  point  termed  the  datum,  this  height 
being  indicated  by  the  figures  written  against  the  line. 

The  intervals  between  the  lines  vertically  is  equal  and  may  be 
1,  3,  5,  10,  or  more  feet  apart ;  5  feet  will  be  found  the  most  useful. 

The  rate  of  inclination  of  the  ground  may  be  estimated  by  the 
relative  proximity  or  distance  apart  of  the  lines.  Where  the  ground 
is  comparatively  level  they  are  far  apart;  where  the  surface  is  very 
hilly  they  lie  close  together. 

These  lines  by  their  greater  or  less  distance  apart  have  the  effect 
of  shading,  and  make  apparent  to  the  eye  the  undulations  and 
irregularities  in  the  surface  of  the  country. 

Fig.  42  shows  an  imaginary  tract  of  country  the  physical  features 
of  which  are  shown  by  contour  lines. 

570.  Map. — The  map  should  show  the  lengths  and  direction  of 
the  different  portions  of  the  line,  the  topography,  rivers,  water- 
courses, roads,  railroads,  and  other  matters  of  interest,  such  as  town 
and  county  lines,  dividing  lines  between  property,  timbered  and 
cultivated  lands,  etc. 

Any  convenient  scale  may  be  adopted;  400  feet  to  an  inch  will 
be  found  the  most  useful. 

Fig.  43  shows  a  map  of  this  kind. 

571.  Memoir. — The  descriptive  memoir  should  give  with  minute- 
ness all  information  such  as  the  nature  of  the  soil,  character  of  the 
several  excavations  whether  earth  or  rock,  and  such  particular  fea- 
tures as  cannot  clearly  be  shown  on  the  map  or  profile. 

Special  information  should  be  given  concerning  the  rivers 
crossed,  as  to  their  width,  depth  at  highest  known  flood,  velocity  of 
current,  character  of  banks  and  bottom,  and  the  angle  of  skew 
which  the  course  makes  with  the  line  of  the  road. 

572.  Levels. — Levels  should  be  taken  along  the  course  of  each 
line,  usually  at  every  100  feet,  or  at  closer  intervals  depending  upon 
the  nature  of  the  country. 

In  taking  the  levels,  the  heights  of  all  existing  roads,  railroads, 
rivers,  or  canals  should  be  noted.  "  Bench-marks  "  should  be  es- 
tablished at  least  every  half-mile  that  is,  marks  made  on  any  fixed 
object  such  as  a  gate-post,  side  of  a  house,  or,  in  the  absence  of  these, 
a  cut  made  on  a  large  tree.  The  height  and  exact  description  of  each 
bench-mark  should  be  recorded  in  the  level  book. 

573.  Cross-levels. — Wherever     considered  necessary  levels    at 


LOCATION    OF    COUNTRY    KOADS. 


393 


394 


HIGHWAY    CONSTRUCTION. 


X 


X 


X 


El 


LOCATION    OF    COUNTRY    ROADS. 


395 


ons- 


right  angles  to  the  centre  line  should 
be  taken.  These  will  be  found  useful 
in  showing  what  effect  a  deviation  to 
the  right  or  left  of  the  surveyed  line 
would  have.  Cross-levels  should  be 
taken  at  the  intersection  of  all  roads 
and  railroads  to  show  to  what  extent, 
if  any,  these  levels  will  have  to  be 
altered  to  suit  the  levels  of  the  pro- 
posed road. 

574.  Profile. — A  profile  is  a  longi- 
tudinal section  of  the  route,  made  from 
the  levels.    Its  horizontal  scale  should 
be  the  same  as  that  of  the  map;  the 
vertical   scale   should   be  such  as  will 
show  with  distinctness  the  inequalities 
of  the  ground. 

Fig.  44  shows  the  manner  in  which 
a  profile  is  drawn  and  the  nature  of 
the  information  to  be  given  upon  it. 

575.  Bridge  Sites. — The  question  of 
choosing  the  site  of  bridges  is  an  im- 
portant one.     If  the  selection  is  not 
restricted  to  a    particular  point,  the 
river  should   be   examined  for   a   con- 
siderable distance  above  and  below  what 
would  be  the  most  convenient  point  for 
crossing;  and  if  a  better  site  is  found, 
the  line  of  the  road  must  be  made  sub- 
ordinate  to   it.     If  several  practicable 
crossings  exist,  they  must  be  carefully 
compared  in  order  to  select  the  one 
most  advantageous.     The  following  are 
controlling  conditions :    (1)  Good  char- 
acter of  the  river-bed,  affording  a  firm 
foundation.     If    rock  is  present   near 
the  surface  of  the  river-bed,  the  foun- 
dation will  be  easy  of  execution   and 
stability  and  economy  will  be  insured. 


-OttP- 


VO'09- 


396  HIGHWAY    CONSTRUCTION. 

(2)  Stability  of  the  river-banks,  thus  securing  a  permanent  con- 
centration of  the  waters  in  the  same  bed.  (3)  The  axis  of  the 
bridge  should  be  at  right  angles  to  the  direction  of  the  current. 
(4)  Bends  in  the  river  are  not  suitable  localities  and  should  be 
avoided  if  possible.  A  straight  reach  above  the  bridge  should  be 
secured  if  possible. 

576.  Principles  to  be  observed  in  making  the  Final  Selection. 

In  making  the  final  selection  the  following  principles  should  be 
observed  as  far  as  practicable. 

(a)  To  follow  that  route  which  affords  the  easiest  grades.     The 
easiest  grade  for  a  given  road  will  depend  upon  the  kind  of  cover- 
ing adopted  for  its  surface 

(b)  To  connect  the  places  by  the  shortest  and  most  direct  route 
commensurate  with  easy  grades. 

(c)  To  avoid  all  unnecessary  ascents  and  descents.     When  a  road 
is  encumbered  with  useless    ascents,  the  wasteful  expenditure  of 
power  is  considerable. 

(d)  To  give  the  centre  line  such  a  position,  with  reference  to 
the  natural  surface  of  the  ground,  that  the  cost  of  construction 
shall  be  reduced  to  the  smallest  possible  amount. 

(e)  To  cross  all  obstacles  (where  structures  are  necessary)  as 
nearly  as  possible  at  right  angles.     The  cost  of  skew  structures  in- 
creases nearly  as  the  square  of  the  secant  of  the  obliquity. 

(/)  To  cross  ridges  through  the  lowest  pass  which  occurs. 

(g)  To  cross  either  under  or  over  railroads;  for  grade  crossings 
mean  danger  to  every  user  of  the  highway.  Guards  and  gates  fre- 
quently fail  to  afford  protection,  and  the  daily  press  is  filled  with 
accounts  of  accidents  more  or  less  serious;  and  while  statistics  fail 
to  give  total  casualties,  the  aggregate  must  be  great. 

577.  Examples  of  Cases  to  be  Treated. — In  laying  out  the  line 
of  a  road,  there  are  three  cases  which  may  have  to  be  treated,  and 
each  of  these  is  exemplified  in  the  contour  map  Fig.  42,  page  393 
First,  the  two  places  to  be  connected,  as  the  towns  A  and  B  on  the 
plan,  may  be  both  situated  in  the  same  valley,  and  upon  the  same 
side  of  it;  that  is,  they  are  not  separated  from  each  other  by  the 
main  stream  which  drains  the  valley.     This  is  the  simplest  case. 
Secondly,  although  both  in  the  same  valley,  the  two  places  may  be  on 
opposite  sides  of  the  valley,  as  at  A  and  0,  being  separated  by  the 
main  river.    Thirdly,  they  may  be  situated  in  different  valleys,  sep- 


LOCATION    OF    COUNTRY    KOADS.  397 

arated  by  an  intervening  ridge  of  ground  more  or  less  elevated,  as  at 
A  and  D.  In  laying  out  an  extensive  line  of  road,  it  frequently 
happens  that  all  these  cases  have  to  be  dealt  with;  frequently,  per- 
haps, during  its  course. 

The  most  perfect  road  is  that  of  which  the  course  is  perfectly 
straight  and  the  surface  practically  level;  and,  all  other  things 
being  the  same,  that  is  the  best  road  which  answers  nearest  to  this 
description. 

Now  in  the  first  case,  that  of  the  two  towns  situated  on  the  same 
side  of  the  main  valley,  there  are  two  methods  which  may  be  pur- 
sued in  forming  a  communication  between  them.  A  road  follow- 
ing the  direct  line  between  them,  shown  by  the  thick  dotted  line 
AB,  may  be  made,  or  a  line  may  be  adopted  which  will  gradually 
and  equally  incline  from  one  town  to  the  other,  supposing  them  to 
be  at  different  levels,  or  which  should  keep,  if  they  are  on  the  same 
level,  at  that  level  throughout  its  entire  course,  following  all  the 
sinuosities  and  curves  which  the  irregular  formation  of  the  country 
may  render  necessary  for  the  fulfilment  of  these  conditions. 
According  to  the  first  method,  a  level  or  uniformly  inclined  road 
might  be  made  from  one  to  the  other;  this  line  would  cross  all  the 
valleys  and  streams  which  run  down  to  the  main  river,  thus  neces- 
sitating deep  cuttings,  heavy  embankments,  and  numerous  bridges; 
or  these  expensive  works  might  be  avoided  by  following  the  sinu- 
osities of  the  valley.  When  the  sides  of  the  main  valley  are  pierced 
by  numerous  ravines  with  projecting  spurs  and  ridges  intervening, 
instead  of  following  the  sinuosities,  it  will  be  found  better  to  make 
a  nearly  straight  line  cutting  through  the  projecting  points  in  such 
a  way  that  the  material  excavated  should  be  just  sufficient  to  fill 
the  hollows. 

Now,  of  all  these,  the  best  is  the  straight  and  uniformly  in- 
clined, or  the  level  road,  although  at  the  same  time  it  is  the  most 
expensive.  If  the  importance  of  the  traffic  passing  between  the 
places  is  not  sufficient  to  warrant  so  great  an  outlay,  it  will  become 
a  matter  of  consideration  whether  the  course  of  the  road  should  be 
kept  straight,  its  surface  being  made  to  undulate  with  the  natural 
i'ace  of  the  country;  or  whether,  a  level  or  equally  inclined  line 
being  adopted,  the  course  of  the  road  should  be  made  to  deviate 
from  the  direct  line  and  follow  the  winding  course  which  such  a 
condition  is  supposed  to  necessitate. 


398  HIGHWAY    CONSTRUCTIONS 

In  the  second  case,  that  of  two  places  situated  on  opposite  sides 
of  the  same  valley,  there  is,  in  like  manner,  the  choice  of  a  per- 
fectly straight  line  to  connect  them,  which  would  probably  require 
a  high  embankment  if  the  road  was  kept  level,  or  steep  inclines  if 
it  followed  the  surface  of  the  country;  or  by  winding  the  road,  it 
may  be  carried  across  the  valley  at  a  higher  point,  where,  if  the 
level  road  be  taken,  the  embankment  would  not  be  so  high,  or,  if 
kept  on  the  surface,  the  inclination  would  be  reduced. 

In  the  third  case,  there  is,  in  like  manner,  the  alternative  of 
carrying  the  road  across  the  intervening  ridge  in  a  perfectly  straight 
line,  or  of  deviating  it  to  the  right  and  left,  and  crossing  the  ridge  at 
a  point  where  the  elevation  is  less. 

The  proper  determination  of  the  question  which  of  these 
courses  is  the  best  under  certain  circumstances  involves  a  con- 
sideration of  the  comparative  advantages  and  disadvantages  of 
inclines  and  curves.  What  additional  increase  in  the  length  of  a 
road  would  be  equivalent  to  a  given  inclined  plane  upon  it;  or,, 
conversely,  what  inclination  might  be  given  to  a  road  as  an 
equivalent  to  a  given  decrease  in  its  length  ?  To  satisfy  this  ques- 
tion it  is  requisite  to  know  the  comparative  force  required  to  draw 
different  vehicles  with  given  loads  upon  level  and  upon  variously 
inclined  roads — a  subject  which  is  treated  in  Chapter  X. 

The  route  which  will  give  the  most  general  satisfaction  con- 
sists in  following  the  valleys  as  much  as  possible  and  rising  after- 
ward by  gentle  grades.  This  course  traverses  the  cultivated  lands, 
regions  studded  with  farm-houses  and  factories.  The  value  of  such 
a  line  is  much  more  considerable  than  that  of  a  route  by  the 
ridges.  The  water-courses  which  flow  down  to  the  main  valley 
are,  it  is  true,  crossed  where  they  are  the  largest,  and  require  works- 
of  large  dimensions,  but  also  they  are  fewer  in  number. 

578.  Intermediate  Towns. — Suppose  that  it  is  desired  to  form  a 
road  between  two  distant  town's,  A  and  B,  Fig.  45,  and  let  us 
for  the  present  neglect  altogether  the  consideration  of  the  physical 
features  of  the  intervening  country,  assuming  that  it  is  equally 
favorable  whatever  line  we  select.  Now  at  first  sight,  it  would  ap- 
pear that  under  such  circumstances  a  perfectly  straight  line  drawn 
from  one  town  to  the  other  would  be  the  best  that  could  be  chosen. 
On  more  careful  examination,  however,  of  the  locality,  we  may  find 
that  there  is  a  third  town,  C,  situated  somewhat  on  one  side  of  the 


LOCATION  OF  COUNTRY  ROADS.  399 

straight  line  which  we  have  drawn  from  A  to  B  ;  and  although  our 
primary  object  is  to  connect  only  the  two  latter,  that  it  would 
nevertheless  be  of  considerable  service  if  the  whole  of  the  three 


./'    "X 

•    X 

,  \  • 

A  D  B 

FIG.  45. 

towns  were  put  into  mutual  connection  with  each  other.  Now  this 
may  be  effected  in  three  different  ways,  any  one  of  which  might, 
under  the  circumstances,  be  the  best.  In  the  first  place,  we  might, 
as  originally  suggested,  form  a  straight  road  from  A  to  B,  and  in  a 
similar  manner  two  other  straight  roads  from  A  to  C,  and  from  B 
to  C,  and  this  would  be  the  most  perfect  way  of  effecting  the 
object  in  view,  the  distance  between  any  two  of  the  towns  being 
reduced  to  the  least  possible.  It  would,  however,  be  attended  with 
considerable  expense,  and  it  would  be  requisite  to  construct  a  much 
greater  length  of  road  than  according  to  the  second  plan,  which 
would  be  to  form,  as  before,  a  straight  road  from  A  to  B,  and  from 
C  to  construct  a  road  which  should  join  the  former  at  a  point  D, 
so  as  to  be  perpendicular  to  it.  The  traffic  between  A  or  B  and  0 
would  proceed  to  the  point  D  and  then  turn  off  to  C.  With  this 
arrangement,  while  the  length  of  the  roads  would  be  very  materi- 
ally decreased,  only  a  slight  increase  would  be  occasioned  in  the 
distance  between  C  and  the  other  two  towns.  The  third  method 
would  be  to  form  only  the  roads  AC  and  CB,  in  which  case  the  dis- 
tance between  A  and  B  would  be  somewhat  increased,  while  that 
between  AC  or  B  and  C  would  be  diminished,  and  the  total  length 
of  road  to  be  constructed  would  also  be  lessened. 

As  a  general  rule  it  may  be  taken  that  the  last  of  these  methods 
is  the  best  and  most  convenient  for  the  public  ;  that  is  to  say,  that  if 
the  physical  character  of  the  country  does  not  determine  the 
course  of  the  road,  it  will  generally  be  found  best  not  to  adopt  a 


400  HIGHWAY   CONSTRUCTION". 

perfectly  straight  line,  but  to  vary  the  line  so  as  to  pass  through 
all  the  principal  towns  near  its  general  course. 

579.  Mountain  Koads. — The  location  of  roads  in  mountainous 
countries  presents  greater  difficulties  than  in  an  ordinary  undulating 
country;  the  same  latitude  in  adopting  undulating  grades  and  choice 
of  position  is  not  permissible,  for  the  maximum  gradient  must  be  kept 
before  the  eye  perpetually.     A  mountain  road  has  to  be  constructed 
on  the  maximum  grade  or  at  grades  closely  approximating  it,  and 
but  one  fixed  point  can  be  obtained  before  commencing  the  survey, 
and  that  is  the  lowest  pass  in  the  mountain  range;  from  this  point 
the  survey  must  be  commenced.     The  reason  for  this  is  that  the 
lower  slopes  of  the  mountains  are  flatter  than   those  at   their 
summit ;  they  cover  a  larger  area  and  merge  into  the  valley  in 
diverse  undulations.     So  that  a  road  at  a  foot  of  a  mountain  may  be 
carried  at  will  in  the  desired  direction  by  more  than  one  route, 
while  at  the  top  of  a  mountain  range  any  deviation  from   the 
lowest  pass  involves  increased  length  of  line.     The  engineer  having 
less  command  of  the  ground,  owing  to  the  reduced  area  he  has  to 
deal  with  and  the  greater  abruptness  of  the  slopes,  is  liable  to  be 
frustrated  in  his  attempt  to  get  his  line  carried  in  the  direction  he 
wishes  it  to  follow. 

580.  It  is  a  common  practice  to  run  a  mountain  survey  up-hill, 
but  such  practice  should  be  avoided.     Wherever  an  acute-angled 
zigzag  is  met  with  on  a  mountain  road  near  the  summit,  the  infer- 
ence to  be  drawn  is  that  the  line  being  carried  up-hill  on  reaching 
the  summit  was  too  low  and  the  zigzag  was  necessary  to  reach  the 
desired  pass.     The  only  remedy  in  such  a  case  is  by  a  resurvey 
beginning  at  the  summit  and  running  down-hill.     This  method 
requires  a  reversal  of  the  usual  one.     The  grade  line  is  first  staked 
out  and  its  horizontal  location  surveyed  afterwards.     The   most 
appropriate  instrument  for  this  work  is  a  transit  with  a  vertical 
circle  on  which  the  telescope  may  be  set  to  the  angle  of  the  maxi- 
mum grade. 

581.  Loss  of  Height. — Loss  of  height  is  to  be  carefully  avoided 
in  a  mountain  road.     By  loss  of  height  is  meant  an  intermediate 
rise  in  a  descending  grade.     If  a  descending  grade  is  interrupt  3d 
by  the  introduction  of  an  unnecessary  ascent,  the  length  of  the 
road  will  be  increased  over  that  due  to  the  continuous  grade  by  the 
length  of  the  portion  of  the  road  intervening  between  the  summit 


LOCATION"  OF  COUNTRY  ROADS.  401 

of  the  rise  and  the  point  in  the  road  in  a  level  with  that  rise— a 
length  which  is  double  that  due  on  the  gradient  to  the  height  of 
the  rise.  For  example,  if  a  road  descending  a  mountain  rises  at 
some  intermediate  point  to  cross  over  a  ridge  or  spur,  and  the 
height  ascended  amounts  to  110  feet  before  the  descent  is  con- 
tinued, such  a  road  would  be  just  one  mile  longer  than  if  the 
descent  had  been  uninterrupted;  for  110  feet  is  the  rise  due  to  a 
half-mile  length  at  1 : 24. 

582.  Water  on  Mountain  Roads. — Water  is  needed  by  the  work- 
men and  during  the  construction  of  the  road ;  it  is  also  very  neces- 
sary for  the  traffic,  especially  during  hot  weather;  and  if  the  road 
exceeds  5  miles  in  length  provision  should  be  made  to  have  it 
either  close  to  or  within  easy  reach  of  the  road.     With  a  little  in- 
genuity the  water  from  springs  above  the  road,  if  such  exist,  can  be 
led  down  to   drinking-fountains  for  men,  and  to    troughs    for 
animals. 

In  a  tropical  country  it  would  be  a  matter  for  serious  considera- 
tion if  the  best  line  for  a  mountain  road  10  miles  in  length  or  up- 
wards, but  without  water,  should  not  be  abandoned  in  favor  of  a 
worse  line  with  a  water-supply  available. 

583.  Halting-places. — On  long  lines  of  mountain  roads  halting- 
places  should  be  provided  at  convenient  intervals. 

584.  Alignment. — No  hard  and  fast  rule  can  be  laid  down  for 
the  alignment  of  a  road;  it  will  depend  both  upon  the  character 
of  the  traffic  on  it  and  upon  the  "  lay  of  the  land."    To  promote 
economy  of  transportation  it  should  be  straight;  but  if  straight- 
ness  is  obtained  at  the  expense  of  easy  grades  that  might   have 
been  obtained  by  deflections  and  increase  of  length,  it  will  prove 
very  expensive  to  the  community  that  uses  it. 

585.  Where  curves  are  necessary,  employ  the  greatest  radius  pos- 
sible and  never  less  than  fifty  feet.     They  may  be  circular  or 
parabolic.     The  parabolic  will  be  found  exceedingly  useful  for  join- 
ing tangents  of  unequal  length,  and  for  following  contour  lines ; 
its  curvature  being  least  at  its  beginning  and  ending,  makes  the 
deviations  from  a  straight  line  less  strongly  marked  than  by  a 
circular  arc  (see  Figs.  46  to  49). 

586.  When  a  curve  occurs  on  an  ascent,  the  grade  at  that  place 
must  be  diminished  in  order  to  compensate  for  the  additional 
resistance  of  the  curve. 


402 


HIGHWAY    CONSTRUCTION. 


TYPES  OF  CURVES. 


\vy    SIMPLE   CURVE 


FIG.  49- 
DOUBLE-REVERSE   CURVE 


LOCATION    OF    COUNTRY    ROADS.  403 

587.  The  width  of  the  wheelway  on  curves  must  be  increased. 
This  increase  should  be  one  quarter  of  the  width  for  central  angles 
between  90  and  120  degrees,  and  one  half  for  angles  between  60 
and  90  degrees. 

588.  Excessive  crookedness  of  alignment  is  to  be  avoided,  for 
any  unnecessary  length  causes  a  constant  threefold  waste:  first, 
of  the  interest  of  the  capital  expended  in  making  that  unnecessary 
portion;  secondly,  of  the  ever-recurring  expense  of  repairing  it; 
and  thirdly,  of  the  time  and  labor  employed  in  travelling  over  it. 

589.  The  curving  road  around  a  hill  may  be  often  no  longer 
than  the  straight  one  over  it,  for  the  latter  is  straight  only  with 
reference  to  the  horizontal  plane,  while  it  is  curved  as  to  the  vertp 
cal  plane;  the  former   is   curved  as  to  the  horizonal   plane,  but 
straight  as  to  the  vertical  plane.     Both  lines  curve,  and  we  call  the 
one  passing  over  the  hill  straight  only  because  its  vertical  curva- 
ture is  less  apparent  to  our  eyes. 

590.  The  difference  in  length  between  a  straight  road  and  one 
which  is  slightly  curved  is  very  small.     If  a  road  between  two 
places  ten  miles  apart  were  made  to  curve  so  that  the  eye  could 
nowhere  see  farther  than  one  quarter  of  a  mile  of  it  at  once,  its 
length  would  exceed  that  of  a  straight  road  between  the  same 
points  by  only  about  four  hundred  and  fifty  feet. 

591.  Zigzags. — The   method    of  surmounting   a  height  by  a 
series  of  zigzags,  or  by  a  series  of  reaches  with  practicable  curves 
at  the  turns,  is  objectionable. 

(1)  An  acute-angled  zigzag  obliges  the  traffic  to  reverse   its 
direction  without  affording  it   convenient  room  for  the  purpose. 
The  consequence  is  that  with  slow  traffic  a  single  train  of  vehicles 
is  brought  to  a  stand,  while  if  two  trains  of  vehicles  travelling  in 
opposite  directions  meet  at  a  zigzag  a  block  ensues. 

(2)  With  zigzags  little  progress  is  made  towards  the  ultimate 
destination  of  the  road;  height  is  surmounted,  but  horizontal  dis- 
tance is  increased  for  which  there  is  no  necessity  or  compensation. 

(3)  Zigzags  are  dangerous.     In  case  of  a  runaway  down-hill  the 
zigzag  must  prove  fatal. 

(4)  If  the  drainage  cannot  be  carried  clear  of  the  road  at  the 
end  of  each  reach,  it  must  be  carried  under  the  road  in  one  reach 
only  to  appear  again  at  the  next,  when  a  second  bridge,  culvert,  or 
drain  will  be  required,  and  so  on  at  the  other  reaches.     If  the 


404  HIGHWAY    CONSTRUCTION. 

-drainage  can  be  carried  clear  at  the  termination  of  each  reach,  the 
lengths  between  the  curves  will  be  very  short,  entailing  numerous 
sigzag  curves,  which  are  expensive  to  construct  and  maintain. 

592.  Final  Location. — The  route  being  finally  determined  upon, 
it  requires  to  be  located.    This  consists  in  tracing  the  line,  placing  a 
;stake  at  every  100  feet  on  the  straight  portions  and  at  every  50  or 
;25  feet  on  curves.     At  the  tangent  points  of  curves,  and  at  points 
•of  compound  and  reverse  curves,  a  larger  and  more  permanent  stake 
.should  be  placed.    Lest  those  stakes  should  be  disturbed  in  the  pro- 
cess of  construction,  their  exact  distance  from  several  points  out- 
side of  the  ground  to  be  occupied  by  the  road  should  be  carefully 
measured  and  recorded  in  the  note-book,  that  they  may  be  replaced. 
The  stakes  above  referred  to  show  the  position  of  the  centre  line 
of  the  road,  and  form  the  base  line  from  which  all  operations  of 
construction  are  carried  on.     Levels  are  taken  at  each  stake,  and 
cross-levels  are  taken  at  every  change  of  longitudinal  slope. 

593.  Construction  Profile. — The  construction  or  working  profile 
is  made  from  the  levels  obtained  on  location.    It  should  be  drawn  to 
a  horizontal  scale  of  400  feet  to  the  inch  and  a  vertical  scale  of  20 
feet  to  the  inch.     Fig.  50  represents  a  portion  of  such  a  profile. 
The  figures  in  column  A  represent  the  elevation  of  the  ground  at 
every  100  feet,  or  where  a  stake  has  been  driven,  above  datum. 
The  figures  in  column  B  are  the  elevations  of  the  grade  above 
<datum.     The  figures  in  column  C  indicate  the  depth  of  cutting  or 
Jieight  of  fill;  they  are  obtained  by  taking  the  difference  between 
the  level  of  the  surface  of  the  ground  and  the  level  of  the  road. 
The  two  straight  parallel  lines  represent  the  grade  of  the  road ;  the 
upper  line  is  intended  to  show  the  upper  surface  of  the  road  when 
finished,  while  the  lower  line  represents  what  is  termed  the  sub- 
grade  or  formation  level.     All  the  dimensions  refer  to  the  forma- 
tion level,  to  which  the  surface  of  the  ground  is  to  "be  formed  to 
;receive  the  road-covering. 

At  all  changes  in  the  rate  of  incliration  of  the  grade  line  a 
Jieavier  vertical  line  should  be  drawn. 

594.  Gradient. — The  grade  of  a  line  is  its  longitudinal  slope, 
&nd  is  designated  by  the  proportion  between  its  length  and  the 
difference  of  height  of  its  two  extremes.     The  ratio  of  these  two 
quantities  gives  it  its  name :  if  the  road  ascends  or  falls  one  foot  in 
every  twenty  feet  of  its  length,  it  is  said  to  have  a  grade  of  1  :  20 


LOCATION   OF   COUXTKY   ROADS. 


406  HIGHWAY    CONSTRUCTION. 

or  a  5  per  cent  grade.  Grades  are  of  two  kinds,  maximum  and 
minimum.  The  maximum  is  the  steepest  which  is  to  be  permitted 
and  which  on  no  account  is  to  be  exceeded.  The  minimum  is  the 
least  allowable  for  good  drainage.  (For  method  of  designating 
grades  see  Table  LXIII.) 

595.  Determination  of  Gradients. — The  maximum  grade  is  fixed 
by  two  considerations,  one  relating  to  the  power  expended  in  as- 
cending, the  other  to  the  acceleration  in  descending  the  incline. 

There  is  a  certain  inclination,  depending  upon  the  degree  of  per- 
fection given  to  the  surface  of  the  road,  which  cannot  be  exceeded 
without  a  direct  loss  of  tractive  power.  This  inclination  is  that  in 
descending  which,  at  a  uniform  speed,  the  traces  slacken,  or  which 
causes  the  vehicles  to  press  on  the  horses;  the  limiting  inclination 
within  which  this  effect  does  not  take  place  is  the  angle  of  repose. 

596.  The  angle  of  repose  for  any  given  road-surface  can  be 
easily  ascertained  from  the  tractive  force  required  upon  a  level 
with  the  same  character  of  surface.     Thus  if  the  force  necessary 
on  a  level  to  overcome  the  resistance  of  the  load  is  ^  of  its  weight, 
then  the  same  fraction  expresses  the  angle  of  repose  for  that  sur- 
face. 

597.  On  all  inclines  less  steep  than  the  angle  of  repose  a  cer- 
tain amount  of  tractive  force  is  necessary  in  the  descent  as  well  as 
in  the  ascent,  and  the  mean  of  the  two  drawing  forces,  ascending 
and  descending,  is  equal  to  the  force  along  a  level  road.     Thus  on 
such  inclines  as  much  mechanical  force  is  gained  in  the  descent  as 
is  lost  in  the  ascent.     From  this  it  might  be  inferred  that  when  a 
vehicle  passes  alternately  each  way  along  the  road,  no  real  loss  is 
occasioned  by  the  inclination  of  the  road;  such  is  not,  however, 
practically  the  fact  with  animal  power,  for  whilst  it  is  necessary  in 
the  ascending  journey  to  have  either  a  less  or  a  greater  number  of 
horses  than  would  be  requisite  if  the  road  were  entirely  level,  no 
corresponding  reduction  can  be  made  in  the  descending  journey. 
On  inclines  which  are  more  steep  than  the  angle  of  repose,  the  load 
presses  on  the  horses  during  their  descent,  so  as  to  impede  their 
action,  and  their  power  is  expended  in  checking  the  descent  of  the 
load;  or  if  this  effect  be  prevented  by  the  use  of  any  form  of  drag 
or  brake,  then  the  power  expended  on  such  drag  or  brake  corre- 
sponds to  an  equal  quantity  of  mechanical  power  expended  in  the 
ascent,  for  which  no  equivalent  is  obtained  in  the  descent. 


LOCATION   OF    COUNTRY   ROADS.  407 

598.  Men  and  all  animals  can  ascend  steeper  slopes  than  they 
<3an  descend.     A  man  walks  slowly  up-hill  and  quickly  down-hill. 
A  horse  does  the  reverse :  the  steeper  the  ascent  the  faster,  until 
fatigued,  he  attempts  to  travel,  while  in  descending  he  moves  at  a 
slow  trot  which  gradually  subsides  into  a  walk.     Consequently  the 
inclination  which  admits  of  high  speed  in  descending  practically 
controls  the  maximum  grade. 

599.  The  maximum  grade  for  a  given  road  will  depend  (1)  upon 
the  class  of  traffic  that  will  use  it,  whether  fast  and  light,  slow  and 
heavy,  or  mixed,  consisting  of  both  light  and  heavy;  (2)  upon  the 
character  of  the  pavement  adopted;  and  (3)  upon  the  question  of 
cost  of  construction.     Economy  of  motive  power  and  low  cost  of 
construction  are  antagonistic  to  each  other,  and  the  engineer  will 
have  to  weigh  the  two  in  the  balance. 

600.  It  is  evident,  therefore,  that  no  fixed  maximum  gradient 
can  be  adopted  in  all  situations. 

For  fast  and  light  traffic  the  grades  should  not  exceed  2  per 
cent;  for  mixed  traffic  3  per  cent  may  be  adopted;  while  for  slow 
traffic  combined  with  economy  5  per  cent  should  not  be  exceeded. 
This  grade  is  practicable  but  not  convenient. 

601.  The  maximum  grade  for  various  paving  materials  is  as 
follows : 

Stone  blocks all  grades 

Wood 5  per  cent 

Asphalt 2*      " 

Brick 5 

Broken  stone 3        " 

602.  The  maximum  grade  adopted  by  the  French  engineers  for 
macadamized  roads  is  5  per  cent  or  1  :  20.  The  maximum  adopted 
by  Telford  was  1  :  30. 

603.  It  is  obvious  from  Table  LVIII  that  the  smoother  the  road- 
surface  the  easier  must  be  the  grade.     From  this  fact  it  has  been 
deduced  that  on  rough-surfaced  roads  steeper  grades  are  permissi- 
ble than  on  smooth  roads.     This  deduction  is  misleading.     The 
force  of  gravity  which  has  to  be  overcome  is  the  same  whether  the 
road-surf  ace  be  rough  or  smooth.    The  rough  surface  affords  better 
foothold  for  the  horse  than  the  smooth  surface,  and  thus  assists 
him  to  exert  his  utmost  force,  but  the  great  friction  produced  be- 
tween the  wheels  and  the  rough  surface  requires  the  expenditure 


408  HIGHWAY   CONSTRUCTION. 

of  greater  tractive  force  than  would  be  required  on  a  smooth  sur- 
face. In  practice  there  is  no  pavement  which  combines  the  oppo- 
site requirements  of  an  even  smooth  surface  for  the  wheels  and  a 
sufficiently  rough  surface  affording  good  foothold  for  the  horses, 
and  a  compromise  of  advantages  must  therefore  be  made  in  most 
cases.  Where  the  extent  and  importance  of  the  traffic  will  warrant 
the  expense,  stone  trackways  afford  an  excellent  method  for  over- 
coming the  disadvantage  of  smooth  pavements  on  inclines. 

604.  To  Determine  the  Maximum  Grade. — Let  L  denote  the 
gross  load  to  be  hauled  up  an  incline;  /,  the  proportion  of  the 
resistance  to  the  load  on  a  level;  8,  the  sine  of  the  angle  of  the 
incline.  Then  (f-}-S).Lis  the  greatest  resistance  to  be  overcome 
in  ascending  the  incline ;  and  this  should  not  exceed  the  greatest 
tractive  force  which  the  horse  is  capable  of  exerting.  Let  P  be 
that  force ;  then  (/  -j-  8)  .  L  should  not  be  greater  than  P,  or  8 

p 
should  not  be  greater  than  -=-  —  /.     This  condition  is  essential  and 

±j 

fixes  the  maximum  grade. 

To  avoid  excessive  acceleration  of  speed  in  descending  S  should 
not  exceed/. 

The  proportion  of  the  resistance/ differs,  as  shown  in  Table  LXI 
very  much  for  different  sorts  of  road  coverings.  It  consists  of  two 
parts,  one  arising  from  friction  and  another  arising  from  vibration, 
and  increases  with  the  velocity  of  transit. 

TABLE  LXI. 
VALUE  OF/. 

Stone  pavement 0.015  =  ^ 

Broken  stone 0.020  =  -fa 

Gravel  road 0.067  =  TV 

Soft  sand  and  loose  gravel 0.143  =  j 

For  the  allowable  maximum  grade  Bockelberg  proposes  the 
following  expression : 

2ju£  =  >u<2 +  (£+£)  tan  a^ 
in  which  /*  =  the  coefficient  of  resistance  to  traction ; 

Q  =  the  load,  including  the  weight  of  the  wagon; 

G  =  the  mean   weight    of    the    horse  =  165  X  5  =  825 

pounds. 
a  =  angle  of  inclination. 


LOCATION   OF    COUNTRY   ROADS.  409 


The  mean  tractive  power  (k)  of  the  horse  is  taken  at  one-fifth 
of  its  weight  =  168  pounds,  which  enables  the  animal  to  move  on 
a  level  plane  a  load  Q  equal  to  its  tractive  pull  divided  by  the 
coefficient  of  resistance;  that  is, 

n      K  165 

Q  =  •— ;  or,  in  the  average  horse,  -  -  pounds. 

On  macadamized  roads  having  a  coefficient  of  ^  a  horse  will 
pull  without  exertion  Q  =  165  -f-  -fa-  =  4950  pounds. 

The  maximum  allowable  grade  depends  upon  the  Additional 
effort  that  a  horse  is  able  to  exert  above  its  mean  tractive  pull,  and 
it  is  generally  conceded  that  on  grades  of  moderate  length,  not  over 
2300  feet,  it  may  exert  twice  the  amount  of  the  adopted  mean. 
Now  since  ^.Q  expresses  the  mean  tractive  force,  we  have  2fiiQ  for 
the  maximum  pull,  which  must  equal  the  weight  of  the  load, 
wagon,  and  horse,  corrected  for  the  grade,  and  the  character  of 
road-surface,  or  ZjuQ  =  nQ  cos  a  -j-  (Q  +  G)  sin  a. 

This  expression  may  be  simplified  by  dropping  cos  a  from  the 
first  member,  because  on  inclinations  up  to  1  in  10  it  remains  nearly 
unity;  and  in  the  second  member  the  term  sin  a  may  be  changed 
into  tan  a,  for  the  reason  that  their  difference  is  too  small  to  affect 
the  result,  and  the  tangent  has  the  advantage  of  expressing  in  a 
more  direct  manner  the  amount  of  the  grade.  This  reduces  the 
formula  down  to  2//§  =  pQ  -f  (Q  +  G)  tan  a. 

In  the  further  consideration  of  this  subject  the  weight  of  the 
horse  may  be  omitted,  which  is  perfectly  admissible  in  grades  of 
moderate  length.  Then  the  formula  becomes  2j*Q  =  j*Q  -f-  tan  a, 
which  is  ft  —  tan  a. 

This  means  that  the  tangent  of  the  permissible  inclination, 
which  in  a  reach  of  moderate  length  does  not  require  an  additional 
horse  to  overcome  it,  is  equal  to  the  coefficient  of  resistance  to 
traction.  On  a  well-paved  road,  therefore,  where  //  =  -g^-,  rises 
greater  than  1  in  50  ought  not  to  occur,  while  on  poor  earth  roads 
a  grade  of  1  in  10  is  not  excessive.  The  coefficient  of  resistance  to 
traction  for  different  road-surfaces  is  given  in  Table  L,  page  372. 

604a.  To  Determine  the  Most  Advantageous  Grade  (J.  H.  Stried- 
inger  and  Otto  von  Geldern). — Although  the  maximum  permissible 
degree  of  inclination  has  been  set  forth  in  the  foregoing,  it  has  not 

y^<-  c.^L 

OF  THE      TJ 

UNIVERSITY 

OF 


410  HIGHWAY   CONSTRUCTION. 

been  decided  yet  whether  such  grades  are  the  most  advantageous, 
or  whether  it  would  not  be  better  to  adopt  a  still  smaller  grade.  In 
order  to  settle  this  question  definitely,  it  is  proper  to  consider 
every  element  that  affects  the  actual  cost  of  transportation,  and  to 
aim  at  reducing  this  as  much  as  possible. 

The  expenditures  of  moving  a  load  upon  a  highway  depend 
upon : 

1.  The  angle  of  inclination  a. 

2.  The  coefficient  of  resistance  to  road  traction  //. 

3.  The  tractional  force  k  which  draught-animals  are  able  to  ex- 
ert at  a  mean  velocity  c  during  a  mean  working  time  t. 

4.  The  law  according  to  which  the  tractional  power  of  animals 
varies  with  the  change  in  the  mean  velocity  or  working  time. 

In  consideration  of  this  factor,  Mascheck's  formula  has  been 
used,  which  expresses  the  tractive  force  in  this  wise : 


In  order  to  make  this  clear,  it  is  well  to  refer  to  a  short  theo- 
retical consideration  of  this  point.  The  work  L  of  animal  loco- 
motors  is,  like  all  mechanical  work,  the  product  of  a  power  Kl  (the 
tractive  force)  into  the  velocity  v,  and  into  a  certain  element  of 
time  ^during  which  that  power  is  exerted;  therefore  L  =  K^Z. 
These  three  factors  differ  in  every  draught-animal  according  to 
individual  conditions,  but  they  hold  such  a  relation  to  each  other 
that  an  increase  in  tractional  force  diminishes  velocity  and  time; 
an  acceleration  of  the  velocity  reduces  the  force  and  time;  while 
a  more  extended  duration  of  work  will  weaken  the  force  and  lower 
the  velocity. 

The  following  formula  of  Mascheck  has  been  generally  em- 
ployed : 

K,  =  , 


in  which  K  —  a  mean  tractive  force; 

c  =  a  mean  velocity; 
t   =  a  mean  working  time. 


LOCATION    OF    COUNTRY    ROADS.  411 

It  may  be  readily  demonstrated  that  with  these  mean  factors  the 
maximum  work  performed  is 

L  max  =  Kct. 

J£  is  usually  taken  at  165  pounds;  c  =  3.6  feet  per  second;  t  =  8 
.hours.  Then  the  work  done  in  one  hour  will  equal  2,147,310  foot- 
pounds. 

If  the  values  c,  K  and  t,  and  with  them  the  maximum  day's  work, 
oannot  be  reached  (if,  for  instance,  a  greater  velocity  be  required), 
we  must  endeavor  to  obtain  a  relative  maximum,  which  is  tied  to 

v       Z 

the  condition  -;  =  /-• 

6          £ 

Introducing  this  value  reduces  Mascheck's  formula  to  the  ex- 
pression 


This  formula  furnishes  results  in  harmony  with  practical  ex- 
perience as  long  as  the  values  of  K,  c,  and  t  do  not  exceed  the  mean 
Talues  beyond  reasonable  limits.  Bockelberg,  for  instance,  assumes 
o  =  4  feet;  Sganzin  places  the  most  advantageous  velocity  that  an 
animal  will  assume  when  it  is  neither  held  in  nor  urged  on  as 
follows : 

A  heavy  horse,  2.93  feet 

A  lighter  animal,  3.66  feet. 

5.  The  weight  of  the  unloaded  wagon  Q,  the  mean  of  which  has 
been  taken  at  1320  pounds,  =  8K. 

6.  The  weight  of  the  load  Q. 

7.  The  weight  of  the  draught-animal,  taken  at  5JT  =  825  pounds 
for  one  horse. 

8.  The  monetary  value  of  the  daily  work  of  the  animal. 

9.  The  probable  cost  of  both  the  new  roadway  construction  and 
the  maintenance  of  the  highway.     Considering  all  these  factors,  a 
mathematical  deduction  has  led  to  certain  results  that  express  the 
most  advantageous  grade,  which  it  is  not  necessary  to  carry  out  in 
detail  here.     Launhardt,  by  a  careful  analysis  in  this  line,  and  by 
assuming  the  following  .values:  u  =  ^V>   Q  —  1320  pounds,  and  G. 
=  825  pounds,  has  arrived  at  the  following  conclusions: 


412  HIGHWAY    CONSTRUCTION. 

Dependent  upon  the  amount  of  traffic,  and  the  cost  of  construc- 
tion and  maintenance  of  the  highway,  the  most  advantageous  grade 
varies: 

For  mountainous  country  ....................  between  ^V  and  ^ 

"  hilly  country  ........  ....................  between^    "   ^ 

"   level  country  ............................  between^    "    ^ 

and  for  an  ordinary  traffic  on  roads  built  at  an  average  cost: 

In  mountainous  country  .................................  1  :  24 

In  hilly  country  ...................  .  ....................  1  :  80 

In  level  country  ...................  .  ...................  1  :  44 

These  deductions  give  results  somewhat  smaller  than  those  laid 
down  by  the  road  regulations  of  European  countries.  In  one  item, 
in  that  of  hilly  country,  however,  there  is  shown  considerable  devi- 
ation from  practice;  the  others  nearly  agree  with  the  results  of 
theoretical  deduction. 

604b.  Cost  of  Grades.  —  The  increased  cost  of  transportation 
caused  by  grades  may  be  ascertained  approximately  by  the  formula 


in  which  R  =  percentage  of  resistance  to  traction  on  a  level  surface  ; 

/  —  percentage  of  resistance  due  to  inclination  of  grade; 

N=.  number  of  full  one-horse  loads  per  day; 

V  =  value  of  horse,  harness,  and  vehicle,  and 

The  amount  which  can  be  economically  spent  in  reducing  a  grade 
is  found  approximately  by  the  formula 

(I  -A) 


2ft 


-NV, 


in  which  A  =  percentage  of  resistance  due  to  the  inclination  of  the 
lower  grade. 

605.  Grade  of  Mountain  Roads. — Although  mountain  roads  are 
in  general  projected  for  slow  traffic,  yet  as  civilization  and  wealth  in  a 
country  increase,  roads  adapted  to  the  use  of  wheeled  vehicles  gradu- 
ally become  used  by  an  increasing  amount  of  quick  traffic.  Ascend- 
ing grades  of  1 : 20,  1 : 18,  1 : 16  are  too  steep  to  permit  of  carriages 
drawn  by  horses  ascending  for  any  distance  except  at  a  foot-pace. 
Hack  conveyances  with  relays  at  short  distances  can  and  do  pro- 


LOCATION   OF   COUNTRY    ROADS.  413 

ceed  more  rapidly  over  hill  roads  with  these  grades,  but  such  ser- 
vice is  accompanied  with  a  great  amount  of  cruelty  to  the  draught 
animals.  Private  horses  are  not  called  upon  to  work  like  hired 
hackneys,  which  are  supposed  to  be  able  to  do  double  the  work  they 
were  capable  of  in  their  younger,  and  better,  days;  therefore,  con- 
tinuous grades  of  1:  16,  1  :  18,  1  :  20  means,  as  respects  private 
quick  traffic,  its  conversion  into  slow  traffic.  On  the  descent  of 
such  inclinations  horses  can  only  travel  with  safety  at  a  slow 
trot,  which  probably  subsides  into  a  walk  at  the  turns  and  when 
meeting  other  traffic.  To  ride  down  a  slope  of  5  per  cent  for  a  long 
distance  is  disagreeable. 

With  a  gradient  of  4  per  cent  on  a  mountain  road  the  slow 
traffic  would  be  so  well  suited  that  ten  miles  continuous  ascent 
could  be  surmounted  without  a  halt  or  undue  exertion  on  the  part 
of  the  draught  animals.  Such  a  grade  would  not  reduce  quick 
traffic  to  a  walk  throughout  an  ascent,  and  it  would  permit  of 
horses  descending  with  safety  at  six  to  eight  miles  an  hour. 

606.  Minimum  Grade. — From  the  previous    considerations  it 
would  appear  that  an  absolutely  level  road  was  the  one  to  be  sought 
for,  but  this  is  not  so ;  there  is  a  minimum  or  least  allowable  grade 
which  the  road  must  not  fall  short  of,  as  well  as  a  maximum  one 
which  it  must  not  exceed.     If  the  road  was  perfectly  level  in  its 
longitudinal  direction,  its  surface  could   not  be   kept  free  from 
water  without  giving  it  so  great  a  rise  in  its  middle  as  would  ex- 
pose vehicles  to  the  danger  of  overturning. 

The  minimum  grade  established  in  France  by  the  Corps  des 
Ponts  et  Chaussees  is  .008,  or  1  in  125 ;  this  may  be  adopted  as 
the  minimum,  and™ in-  a  perfectly  level  country  the  road  should 
be  artificially  formed  into  gentle  undulations  approximating  this 
minimum  limit. 

607.  Undulating  Grades. — From  the  fact  that  the  power  re- 
quired   to   move   a  load  at   a  given   velocity  on   a  level  •  road  is 
decreased  on  a  descending  grade  to  the  same  extent  that  it  is  in- 
creased in  ascending  the  same  grade,  it  must  not  be  inferred  that 
the  animal  force  expended  in  passing  alternately  each  way  over  a 
rising  and  falling  road  will  gain  as  much  in  descending  the  several 
inclines  as  it  will  lose  in  ascending  them.     Such  is  not  the  case. 
The  animal  force  must  be  sufficient,  either  in  power  or  number,  to 
draw  the  load  over  the  level  portions  and  up  the  steepest  inclines 


414 


HIGHWAY    CONSTRUCTION. 


of  the  road,  and  in  practice  no  reduction  in  the  number  of  horses 
can  be  made  to  correspond  with  the  decreased  power  required  in. 
descending  the  inclines. 

The  popular  theory  that  a  gentle  undulating  road  is  less  f  atigu- 

TABLE  LXII. 
DIFFERENT  METHODS  OF  DESIGNATING  THE  SAME  GRADES. 


American  Method, 
Feet  per  100  feet. 

English  Method. 

Feet  per  Mile. 

Angle  wifch  the 
Horizon. 

* 

:400 

13.2 

0°     8'    36" 

:200 

26.4 

0     17    11 

§ 

:  150 

39.6 

0    22    55 

1 

:100 

52.8 

0    34    23 

U 

:80 

66 

0    42    58 

11 

:66£ 

79.2 

0    51     28 

if 

:57} 

92.4 

1      0    51 

2 

:50 

105.6 

186 

2* 

:44± 

118.8 

1     17    39 

»i 

:40 

132 

1    25    57 

2f 

:36i 

145.2 

1    34    2£ 

3 

:33i 

158.4 

1    43    08- 

3± 

:80f 

171.6 

1     51     42 

3| 

:28£ 

184.8 

2      0    16 

3f 

:26£ 

198 

2      8    51 

4 

:25 

211.2 

2    17    26 

4* 

:23£ 

224.4 

2    26    10 

4| 

:22£ 

237.6 

2    34    36 

4| 

:21 

250.8 

2    43    35 

5 

1  :20 

264 

2    51    44 

6 

1:1*1 

316.8 

3    26    12 

7 

1:141 

369.6 

4      0    15 

8 

l:12i 

422.4 

4    34    26 

9 

1:11* 

475.2 

5      8    31 

10 

1:  10 

528 

5    42    37 

ing  to  horses  than  one  which  is  perfectly  level  is  erroneous.  The* 
assertion  that  the  alternations  of  ascent,  descent,  and  levels  call  into- 
play  different  muscles,  allowing  some  to  rest  while  others  are  ex- 
erted, and  thus  relieving  each  in  turn,  is  demonstrably  false,  and 
contradicted  by  the  anatomical  structure  of  the  horse.  Since  this 
doctrine  is  a  mere  popular  error,  it  should  be  utterly  rejected,  not 
only  because  false  in  itself,  but  still  more  because  it  encourages 
the  building  of  undulating  roads,  and  this  increases  the  labor  and 
cost  of  transportation  upon  them. 

608.  Level  Stretches. —On  long  ascents  it  is  generally  recom- 
mended to  introduce  level  or  nearly  level  stretches  at  frequent  in- 
tervals in  order  to  rest  the  animals.  These  are  objectionable  when. 


LOCATION:  OF  COUNTRY  ROADS. 


415 


they  cause  loss  of  height,  and  animals  will  be  more  rested  by  halt- 
ing and  unharnessing  for  half  an  hour  than  by  travelling  over  a 
level  portion.  The  only  case  which  justifies  the  introduction  of 
levels  into  an  ascending  road  is  where  such  levels  will  advance  the 
road  towards  its  objective  point;  where  this  is  the  case  there  will 
be  no  loss  of  either  length  or  height,  and  it  will  simply  be  exchang- 
ing a  level  road  below  for  a  level  road  above. 

609.  Establishing  the  Grade. — When  the  profile  of  a  proposed 
route  has  been  made,  a  grade  line  is  drawn  upon  it  (usually  in  red) 
in  such  a  manner  as  to  follow  its  general  slope,  but  to  average  its 
irregular  elevation  and  depressions. 

If  the  ratio  between  the  whole  distance  and  the  height  of  the 
line  is  less  than  the  maximum  grade  intended  to  be  used,  this  line 
will  be  satisfactory;  but  if  it  be  found  steeper,  the  cuttings  or  the 
length  of  the  line  will  have  to  be  increased :  the  later  is  generally 
preferable. 

610.  The  apex  or  meeting  point  of  all  curves  should  be  rounded 
off  by  a  vertical  curve  shown  in  Figs.  51  to  53. 

The  formula  for  these  curves  is  given  in  Art.  935. 

EXAMPLES  OF  THE  APPLICATION   OF  VERTICAL  CURVES. 


FIGS.  51    TO  53. 


CHAPTER  XII. 
WIDTH  A.ND  TRANSVERSE  CONTOUR. 

611.  A  road  should  be  wide  enough  to  accommodate  fte  traffic 
for  which   it  is   intended,  and   should   comprise   a  wheelway   for 
vehicles  and  a  space  on  each  side  for  pedestrians. 

612.  The  wheelway  of  country  highways  need  be  no  wider  than 
is  absolutely  necessary  to  accommodate  the  traffic  using  it ;  in  many 
places  a  track  wide  enough  for  a  single  team  is  all  that  is  necessary. 
But  the  breadth  of  the  land  appropriated  for  highway  purposes 
should  be  sufficient  to  provide  for  all  future  increase  of  traffic. 
The  wheelways  of  roads  in  rural  sections  should  be  double ;  that  is, 
one  portion  paved  (preferably  the  centre)  and  the  other  left  with 
the  natural  soil.     The  latter  if  kept  in  repair  will  for  at  least  one 
half  the  year  be  preferred  by  teamsters. 

613.  The  minimum  width  of  the  paved  portion,  if  intended  to 
carry  two  lines  of  travel,  is  fixed  by  the  width  required  to  allow 
two  vehicles  to  pass  each  other  safely.    This  width  is  16  feet.    If  in- 
tended for  a  single  line  of  travel,  8  feet  is  sufficient  but  suitable 
turnouts  must  be  provided  at  frequent  intervals.     The  most   eco- 
nomical width  for  any  roadway  is  some  multiple  of  eight. 

614.  Wide  roads  are  the  best;  they  expose  a  larger  surf  ace  to  the 
drying  action  of  the  sun  and  wind,  and  require  less  supervision  than 
narrow  ones.     Their  first  cost  is  greater  than  narrow  ones,  and  that 
nearly  in  the  ratio  of  the  increased  width. 

615.  The  cost  of  maintaining   a   mile  of  road  depends    more 
upon  the  extent  of  the  traffic  than  upon  the  extent  of  its  surface, 
and  unless  extremes  be  taken  the  same  quantity  of  material  will  be 
necessary  for  the  repair  of  the  road  whether  wide  or  narrow  which 
is  subjected  to  the  same  amount  of  traffic.     The  cost  of  spreading 
the  materials  over  the  wide  road  will  be  somewhat  greater,  but 
the  cost  of  the  materials  will  be  the  same.     On  narrow  roads  the 
traffic,  being  confined  to  one  track,  will  wear  more  severely  than  if 
spread  over  a  wider  surface. 

616.  The  width  of  land  appropriated  for  road  purposes  varies  in 
the  United  States  from  49 J-  to  66  feet;  in  England  and  France 

416 


WIDTH   AND   TRANSVERSE   CONTOUR. 


417 


from  26  to  66  feet.  And  the  width  or  space  macadamized  is  also 
subject  to  variation;  in  the  United  States  the  average  width  is  16 
feet;  in  France  it  varies  between  16  and  22  feet;  in  Belgium  8£  feet 
seems  to  be  the  regular  width,  while  in  Austria  it  varies  from  14£ 
to  26i  feet. 

Figs.  85-92,  pages  461-463,  show  the  subdivision  of  the  mid- 
way into  wheelway,  sidewalks,  and  ditches. 

617.  Width  of  Mountain  Roads. — Mountain  roads  should  be  pro- 
portioned in  width  to  the  amount  of  traffic;  they  should  be  neither 
too  wide  nor  too  narrow.  If  of  excessive  width,  the  cost  of  con- 
struction is  increased ;  if  too  narrow,  traffic  will  be  interrupted  by 
blockades.  An  economical  width  is  24  feet,  and  the  stone  covering 
should  extend  from  gutter  to  gutter.  If  the  center  only  is  covered, 
the  road  will  soon  be  destroyed,  as,  by  reason  of  the  curves  on  a 
mountain  side  predominating  over  straight  reaches,  the  traffic  will 
hug  either  one  side  of  the  road  or  the  other. 

Table  LXIII  shows  the  number  of  acres  required  per  mile  for 
different  widths  of  roadway. 

TABLE  LXIII. 

ACRES   REQUIRED   PER  MlLE   FOR   DIFFERENT   WlDTHS   OF   ROADWAY. 


Width. 
Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

Width. 

Feet. 

Acres 
per  mile. 

Width. 

Feet. 

Acres 
per  mile. 

Width. 
Feet. 

Acres 
per  mile. 

i 

.030 

19 

2.30 

40 

4.85 

59 

7.15 

80 

9.70 

i 

.061 

20 

2.42 

41 

4  97 

60 

7.27 

81 

9.82 

1 

.121 

21 

2.55 

4H 

5.00 

61 

7.39 

82 

9.94 

2 

.242 

22 

2.67 

42 

5.09 

62 

7.52 

82* 

10.00 

3 

.364 

23 

2.79 

43 

5.21 

63 

7.64 

83 

10.06 

4 

.485 

24 

2.91 

v  44 

5.33 

64 

7.76 

84 

10.18 

5 

.606 

24£ 

3.00 

45 

5.45 

65 

7.88 

85 

10.30 

fl 

.727 

25 

3.03 

46 

5.58 

66 

8.00 

86 

10.42 

7 

.848 

26 

3.15 

47 

5.70 

67 

8.12 

87 

10.54 

8 

.970 

27 

3.27 

48 

5.82 

68 

8.24 

88 

10.66 

8| 

1.00 

28 

3.39 

49 

5.94 

69 

8.36 

89 

10.78 

9 

1.09 

29 

3.52 

49£ 

6.00 

70 

8.48 

90 

10.90 

10 

1.21 

30 

3.64 

50 

6.06 

71 

8.61 

90| 

11.00 

11 

1.33 

31 

3.76 

51 

6.18 

72 

8.73 

91 

11.03 

12 

1.46 

32 

3.88 

52 

6.30 

73 

8.85 

92 

11.15 

13 

1.58 

33 

4.00 

53 

6.42 

74 

8.97 

93 

11.27 

14 

1.70 

34 

4.12 

54 

6.55 

74i 

9.00 

94 

11.39 

15 

1.82 

35 

4.24 

55 

6.67 

75 

9.09 

95 

11.51 

16 

1.94 

36 

4.36 

56 

6.79 

76 

9.21 

96 

11.63 

18* 

2.00 

37 

4.48 

57 

6.9t 

77 

9.33 

97 

11.75 

17 

2.06 

38 

4.61 

57f 

7.00 

78 

9.45 

98 

11.87 

18 

2.18 

39 

4.73 

58 

7.03 

79 

9.58 

99 

12.00 

100 

12.12 

418  HIGHWAY   CONSTKUCTION-. 

618.  Transverse  Contour. — The  centre  of  all  roadways  should 
be  higher  than  the  sides.  The  object  of  this  is  to  facilitate  the  flow 
of  the  rain-water  to  the  gutters.  Where  a  good  surface  is  main- 
tained a  very  moderate  amount  of  rise  is  sufficient  for  this  purpose. 
Earth  roads  require  the  most  and  asphalt  the  least.  The  rise  should 
bear  a  certain  proportion  to  the  width  of  the  carriageway.  The 
most  suitable  proportions  for  the  different  paving  materials  is  shown 
in  the  following  table : 

TABLE  LXIV. 
AMOUNT  OF  TRANSVERSE  RISE  REQUIRED  FOR  DIFFERENT  PAVEMENTS.. 

Kind  of  Surface.  Proportion  of  the 

Carriageway  Width. 

Earth  Rise  at  centre ¥V 

Gravel  . 


Broken  stone, 
Stone  blocks. 

Wood 

Brick... 

Asphalt 


•A 

oe 


619.  Form  of  Transverse  Contour. — All  authorities  agree  that 
the   form  should  be  convex,  but  they  differ  in  the  amount   and 
form  of  the  convexity.   Circular  arcs,  two  straight  lines  joined  by  a 
circular  arc  and  ellipses  all  have  their  advocates,  but  the  best  form 
for  streets  will  be  found  to  be  a  parabolic  curve  starting  from  the 
edge  of  the   gutter  next  the  carriageway  or  one  foot   from  the 
curb  line.     Fig.  54  shows  this  form,  which  is  obtained  in  the  fol- 
lowing manner:   Divide  the   ordinate  or  the  width  between  the 
edge  of  the  gutter  and  the  centre  of  the  street  into  10  equal  parts, 
and  raise  perpendiculars  the  length  of  which  will  be  determined 
by  multiplying  the  rise  at  the  center  by  the  respective  number  of 
each  perpendicular  in  the  diagram.     The  amounts  thus  obtained 
can  be  added  to  the  rod  readings,  and  the  stakes  set  at  the  proper 
distance  across  the  street  with  their  tops  at  this  level  will  give  the 
true  curve. 

620.  For  country  roads  a  curve  of  suitable  convexity  may  be 
obtained  as  follows :  Give  -J  of  the  total  rise  at  J  the  width  from 
the  centre  to  the  side,  and  f  of  the  total  rise  at  -£  the  width  (Fig.  55), 

621.  Excessive  height  and  convexity  of  cross-section  contract 
the  width  of  the  wheelway,  by  concentrating  the  traffic  at  the 


WIDTH   AND   TRANSVERSE   CONTOUR. 


419 


TRANSVERSE  CONTOUR  OF  STREETS  AND  ROADS. 


m 

q 

O 

z 


p 

bi 

CJl 
3J 

z 


< 

rn 

w     "%foFAB 
m 


"T 
»^l 


/•oo 


IGUTTER  LEVEL 


420  HIGHWAY   CONSTRUCTION. 

centre,  that  being  the  only  part  where  a  vehicle  can  run  upright. 
The  force  required  to  haul  vehicles  over  such  cross-sections  is 
increased,  because  an  undue  proportion  of  the  load  is  thrown  upon 
two  wheels  instead  of  being  distributed  equally  over  the  four. 
The  continual  tread  of  horses'  feet  in  one  track  soon  forms  a 
depression  which  holds  water,  and  the  continuous  travel  of  vehicles 
in  one  track  soon  wears  ruts  which  retain  water,  and  the  surface  is 
not  so  dry  as  with  a  flatted  section,  which  allows  the  traffic  to  dis- 
tribute itself  over  the  whole  width. 

622.  Sides  formed   of    straight    lines    are  also  objectionable. 
They  wear  hollow,  retain  water,  and  defeat  the  object  sought  by 
raising  the  centre. 

623.  Concave  Form. — In  Triest,  Austria,  the  early  pavements 
were  laid  concave,  i.e.,  inclining  to  the  middle,  along  which,  under 
the  surface-canals  or  sewers  extended  with  gratings  at  intervals  for 
the  admission  of  surface-drainage.     The  same  method,  but  with 
open  channels  through  the  centre,  is  practised  in  several  South 
American  towns.     Experience  has  proved  that  this  plan  is  not 
desirable  or  convenient  for  traffic. 

624.  The  required  convexity  should  be  obtained  by  rounding 
the  formation  surface,  and  not  by  diminishing  the  thickness  of  the 
covering  at  the  sides. 

625.  On  hillside  and  mountain  roads  it  is  generally  recom- 
mended that  the  surface  should  consist  of  a  single  slope  inclining 
inwards.     There   is   no  reason  for   or   advantage   gained  by  this 
method.     The  form  best  adapted  to  these  roads  is  the  same  as  for 
a  road  under  ordinary  conditions,  viz.,  that  described  in  Art.  619. 

626.  With  a  roadway  raised  in  the  centre  and  the  rain-water 
draining  off  to  gutters  on  each  side,  the  drainage  will  be  more 
effectual  and  speedy  than  if  the  drainage  of  the  outer  half  of  the 
road  has  to  pass  over  the  inner  half.     The  inner  half  of  such  road 
is  usually  subjected  to  more  traffic  than  the  outer  half.     If  formed 
of  a  straight  incline,  this  side  will  be  worn  hollow  and  retain  water. 
The  inclined  flat  section  never  can  be  properly  repaired  to  with- 
stand the  traffic.     Consequently  it  never  can  be  kept  in  good  order, 
no  matter  how  constantly  it  may  be  mended.     It  is  always  below 
par.     When  heavy  rain  falls  it  is  seriously  damaged. 


CHAPTER  XIII. 
EARTH-WORK. 

627.  Earth-work. — The  term  "  earth-work  "  is  applied  to  all  the 
operations  performed  in  the  making  of  the  excavations  and  em- 
bankments to  prepare  them  for  receiving  the  road-covering.     In 
its  widest  sense  it  comprehends  work  in  rock  as  well  as  in  the 
looser  material  of  the  earth's  crust. 

628.  Equalizing  Earth-work  is  a  term  applied  to  the  process  of 
so  adjusting  the  formation  or  sub-grade  level  of  an  inter  ied  work 
that  the  earth  from  the  cuttings  shall  be  as  nearly  as  possible 
sufficient  to  make  the  embankments  and  no  more.     The  art  of 
making  this  adjustment  by  the  eye  upon  a  profile  of  the  ground 
with  sufficient  accuracy  is  soon  acquired  by  practice.     In  most 
cases  it  is  essential  to  economy  in  the  cost  of  the  work.     For  any  sur- 
plus of  embankment  over  cutting  must  be  made  up  by  borrowing, 
and  the  earth  from  any  surplus  of  cutting  over  embankment  must 
be  wasted,  both  of  these  operations  involve  additional  cost  for  labor 
and  land.     But  cases  sometimes  occur  in  which  it  is  more  economi- 
cal to  make  an  embankment  from  borrow-pits  close  at  hand  than 
to  bring  the  necessary  material  from  a  far-distant  cutting  on  the 
line  of  the  works,  or  in  which  it  is  more  economical  to  waste  part 
of  the  material  from  a  cutting  than  to  send  it  to  a  far-distant 
embankment  on  the  line  of  the  works,  and  these  points  must  be 
decided  by  the  engineer  to  the  best  of  his  judgment  in  each  par- 
ticular case. 

629.  Transverse  Balancing. — When  the  road  lies  along  the  side 
of  a  hill,  so  that  it  is  partly  in  excavation  and  partly  in  embank- 
ment, it  is  necessary  to  so  place  its  centre  line  that  these  two  parts 
of  cross-section  may  balance.     When  the  ground  has  a  uniform 
slope  the  desired  end  would  be  obtained  (if  the  side  slopes  were  the 
same  for  excavation  and  embankment  and  if  no  shrinkage  existed), 

421 


422  HIGHWAY   CONSTRUCTION. 

by  locating  the  centre  line  of  the  road  upon  the  surface  of  the 
ground.  In  other  cases,  as  when  the  side  of  the  excavation  slopes 
1  to  1  and  that  of  the  embankment  2  to  1,  a  formula  to  determine 
the  position  of  the  centre  line  may  be  readily  established. 

630.  If  earth  be  wanted  for  a  neighboring  embankment,  the 
amount   of   excavation   may   be   easily   increased   by   moving  the 
centre  of  the  road  farther  into  the  hill,  with  the  additional  advan- 
tage of   lessening  its  liability  to  slip.     The  line  may  be  thus 
changed  on  the  map  according  to  the  notes  of  the  cross-section  in 
the  level  book,  and  be  subsequently  moved  by  a  corresponding 
quantity  on  the  ground. 

631.  When  the  slope  of  the  ground  is  very  steep  the  transverse 
balance  must  be  disregarded  and  the  road  made  chiefly  in  excava- 
tion, to  avoid  the  insecurity  of  a  high  embankment. 

632.  Borrow-pits. — When  the  excavations  on  the  line  of  the 
road  do  not  furnish  sufficient  material  for  the  embankments,  the 
deficiency  is  obtained  either  by  widening  the  excavations,  or  from 
an  excavation  termed  a  "  borrow-pit,"  made  in  the  vicinity  of  the 
embankment. 

633.  Spoil-banks. — If  the  excavations   furnish  more   material 
than  is  required  for  the  embankments,  the   excess   is  generally 
deposited  in  a  convenient  place  on  the  land  adjoining  the  excava- 
tion, in  banks  termed  "  spoil-banks." 

Both  these  cases  are  expensive  and  objectionable.  It  is  there- 
fore very  desirable  to  make  the  excavation  and  embankment 
"balance"  each  other.  If  the  calculations  show  much  disparity  in 
the  two  amounts,  the  location  of  the  line  should  be  changed  in 
some  way  so  as  to  eifect  the  desired  equality. 

634.  The   equalization    must,   however,  be    restrained  within 
certain  limits,  for  it  should  evidently  be  abandoned  when,  in  order 
to  form  sufficient  excavation  to  make  the  embankment,  it  would 
be  necessary  to  go  to  such  a  distance  that  the  cost  of  transport 
would  exceed  the  cost  of  borrowing  for  the  banks  and  wasting  the 
distant  excavation  in  spoil-banks. 

635.  The  comparison  of  the  price  of  transport  with  that  of 
excavation  and  land  will  therefore  determine  the  distance  within 
which  the  balancing  must  be  established. 

636.  The  form  to  be  given  to  the  borrow-pits  and  spoil-banks  will 
depend  in  a  great   degree  upon  the  locality  ;  they  should  as  far  as 


EARTH-AVORK.  42  < 


practicable  be  located  so  that  the  cost  of  removal  of  the  earth  shall 
be  the  least  possible. 

637.  Staking  out  Borrow-pits. — Borrow-pits  should  be  staked  out 
by  the  engineer  and  their  contents  calculated,  unless  the  contractor 
is  to  be  paid  by  embankment  measurements.     A  number  of  cross- 
profiles  are  taken  of  the  original  surface,  and   (on  the  same  lines) 
on  the  bottom  of  the  pit,  after  it  is  excavated,  which  furnish  the 
depth  of  cutting  at  each  required  point.     Borrow-pits  should  be 
regularly  excavated  so  that  they  may  not  present  an  unsightly  ap- 
pearance when  abandoned. 

638.  Shrinkage. — The  equality  recommended  must  be   taken 
with  an   important  qualification,  dependent  upon   the  fact  that 
<earth   transferred   from   excavation   to   embankment   shrinks,   or 
settles  so  as  to  occupy  less  space  in  the  bank  than  it  did  in  its 
natural  state. 

Eock,  on  the  contrary,  occupies  more  space  when  broken. 

639.  In  estimating  the  relative  amounts  of  excavation  and  em- 
bankment required,  allowance  must  be  made  for  difference  in  the 
spaces  occupied  by  the  material  before  excavation  and  after  it  is 
settled  in  embankment.     The  shrinkage  of  the  different  materials 
is  about  as  follows  : 

Gravel 8  per  cent 

Gravel  and  saud 9 

Clay  and  clay  earths 10 

Loam  and  light  sandy  earths 12 

Loose  vegetable  soil 15 

Puddled  clay 25 

Rock,  on  the  other  hand,  increases  in  value  by  being  broken  up, 
^and  does  not  settle  again  into  less  than  its  original  bulk.  The  in- 
crease may  be  taken  at  fifty  per  cent. 

Thus  an  excavation  of  loam  measuring  1000  cubic  yards  will 
form  only  about  880  cubic  yards  of  embankment,  or  an  embankmenf 
of  1000  cubic  yards  will  require  about  1120  cubic  yards  measured 
in  excavation  to  make  it.  A  rock  excavation  measuring  1000  yards 
will  make  from  1500  to  1700  cubic  yards  of  embankment,  depend- 
ing upon  the  size  of  the  fragments. 

640.  The  lineal   settlement   of   earth   embankments  will   be 
about  in  the  ratio  given   above;  therefore  either  the  contractor 
should  be  instructed  in  setting  his  poles  to  guide  him  as  to  the 


424  HIGHWAY   CONSTHUCTION. 

height  of  grade  on  an  earth  embankment  to  add  the  required  per- 
centage to  the  fill  marked  on  the  stakes,  or  the  percentage  may  be- 
included  in  the  fill  marked  on  the  stakes.  In  rock  embankments- 
this  is  not  necessary. 

641.  Failure  of  Earth-work. — The  failure  of  earth-work  is  due 
to   the   slipping   or   sliding  of  its  parts  on  each   other,   and   its 
stability  arises  from  resistance  to  the  tendency  so  to  slip. 

In  solid  rock,  that  resistance  arises  from  the  elastic  stress  of  the 
material,  when  subjected  to  a  shearing  force  ;  but  in  the  mass  of 
earth,  as  commonly  understood,  it  arises  partly  from  the  friction 
between  the  grains,  and  partly  from  their  mutual  adhesion;  which 
latter  force  is  considerable  in  some  kinds  of  earth,  such  as  clay,, 
especially  when  moist. 

But  the  adhesion  of  earth  is  gradually  destroyed  by  the  action 
of  air  and  moisture,  and  of  the  changes  of  the  weather,  and  especi- 
ally by  alternate  frost  and  thaw  ;  so  that  its  friction  is  the  only 
force  which  can  be  relied  upon  to  produce  permanent  stability. 

642.  .The  temporary  additional  stability,  however,   which  is. 
produced  by  adhesion,  is  useful  in  the  execution  of  earth-work,  by 
enabling  the  sides  of  a  cutting  to  stand  for  a  time  with  a  vertical 
face  for  a  certain  depth  below  its  upper  edge.     That   depth  is. 
greater,  the  greater  the  adhesion  of  the  earth  as  compared  with  its. 
heaviness  ;  it  is  increased  by  a  moderate  degree  of  moisture,  but 
diminished  by  excessive  wetness. 

The  following  are  some  of  its  values  : 

Greatest  depth  of 

tern.  vert.  face. 
Earth. 

Clean  dry  sand  and  gravel  from 0  to  1  foot. 

Moist  sand  and  ordinary  surface  mould  from 3  "  6  feet 

Clay  (ordinary)  from 10  "  16   " 

Compact  gravel  from ...10  "  15   " 

643.  One  of  the  effects  of  the  temporary  stability  due  to  adhesion 
is  seen  in  the  figure  of  the  surface  left  after  a  "  slip  "  has  taken 
place  in  earth-work.     That  surface  is  not  a  uniform  slope,  inclined 
at  the  angle  of  repose,  but  is  concave  in  its  vertical  section,  being 
vertical  at  its  upper  edge,  and  becoming  less  and  less  steep  down- 
wards.    It  is  not  capable,  however,  of  preserving  that  figure  ;  for 
the  action  of  the  weather,  by  gradually  destroying  the  adhesion  of 
the  earth,  causes  the  steep  upper  part  of  the  concave  face  to  crumble 


EARTH-WORK. 


425 


down,  so  that  the  whole  tends  to  assume  a  uniform  curved  slope  in 
the  end. 

644.  The  Permanent  Stability  of  earth,  which  is  due  to  friction 
alone,  is  sufficient  to  maintain  the  side  either  of  an  embankment 
or  of  a  cutting  at  a  uniform  slope,  whose  inclination  to  the  horizon 
is  the  angle  of  repose,  or  angle  whose   tangent  is  the  coefficient  of 
friction.     This  is  called  the  natural  slope  of  the  earth.     The  cus- 
tomary mode  of  describing  the  slope  of  earth- work  is  to  state  the 
ratio  of  the  horizontal  bueadth  to  its  vertical  height,  which  is  the 
resiprocal  of  the  tangent  of  the  inclination. 

645.  The  angles  of  repose  for  different  earths  are  given  in. 
Table  LXY.     But  for  all  practical  purposes  it  may  be  said  that 
all  earths,  sand,   and   gravel,  stand  at   a   slope  of  33   degrees  41 
minutes,  or  1-J  to  1.     If  the  slopes  of  an  excavation  in  sand  are  to 
be  left  unprotected  by  sodding,  they  should  be  given  a  slope  of  2£ 
to  1.     The  ratio  of  slopes,  their  angles  and  length,  are  given  in 
Table  LXVI. 

TABLE  LXV. 
NATURAL  SLOPES  OF  EARTHS  (WITH  HORIZONTAL  LINE). 

Gravel  (average). 40  degrees 

Dry  sand 38 

Wet    "    % 22 

Vegetable  earth ^.28 

Compact  earth , 50 

Shingle -.39 

Rubble 45 

Clay  (well  drained). 45 

"    (wet) 16 


TABLE  LXVI. 

LENGTHS  AND  ANGLES  OP  SLOPES. 


Slope. 

Angle 
with  Horizon 

Length. 
(Height  taken  as  1.00.) 

Slope. 

Angle 
with  Horizon 

Length. 
(Height  taken  as  1.00). 

i    1 

75°  58' 

1.0307 

U:l 

33°  41' 

1.802 

*    1 

63    26 

1.118 

lf:l 

29    44 

2.016 

*    1 

53      8 

1.25 

2    :  1 

26    34 

2.236 

1      1 

45      0 

1.4142 

3    :1 

18    26 

3.162 

U:l 

38    40 

1.6 

4    :  1 

14     2 

4.124 

426  HIGHWAY    CONSTRUCTION. 

646.  The  inclinations  generally  given  in  practice  to  the  various 
materials  are  as  follows  : 

Loose  earth,  loam  and  gravel 1$  to  1 

Sand 2    '  <  1 

Soft  greasy  clay 3    "  1 

Rock  (sound) OJ  "  1 

647.  Effect  of  Moisture. — The  presence  of  moisture  in  earth  to 
an  extent  just  sufficient  to  expel  the  air  from  its  crevices  seems  to 
increase  its  coefficient    of  friction  [slightly;   but  any  additional 
moisture  acts  like  a  lubricant  in  diminishing  friction,  and  tends 
to  reduce  the  earth  to  a  semi-fluid  condition,,  or  to  the  state  of 
mud.     In  this  state,  although  it  has  some  cohesion,  or  viscidity, 
which  resists  rapid  alteration  of  form,  it  has  no  frictional  stability; 
and  its  coefficient  of  friction    and  angle  of  repose,    are  each  of 
them  null. 

Hence  it  is  obvious  that  the  frictional  stability  of  earth  depends 
to  a  great  extent  on  the  ease  with  which  the  water  that  it  occasion- 
ally absorbs  can  be  drained  way.  The  safest  materials  for  earth- 
work are  fragments  of  rock,  shingles,  gravel,  and  clean  sand ;  for 
these  materials  allow  water  to  pass  through  without  retaining  more 
of  it  than  is  beneficial.  The  cleanest  sand,  however,  may  be  made 
completely  unstable  and  reduced  to  the  state  of  "  quick  sand  "  if 
it  is  contained  in  a  basin  of  water-holding  materials  so  that  water 
mixed  amongst  its  particles  cannot  be  drained  off. 

The  property  of  retaining  water  and  forming  a  paste  with  it 
belongs  specially  to  clay,  and  to  earths  of  which  clay  is  an  ingre- 
dient. Such  earths,  how  hard  and  firm  soever  they  may  be  when 
first  excavated,  are  gradually  softened,  and  have  both  their  fric- 
tional stability  and  their  adhesion  diminished  by  exposure  to  the 
air.  In  this  respect  mixtures  of  sand  and  clay  are  the  worst ; 
for  the  sand  favors  the  access  of  water,  and  the  clay  prevents  its 
escape. 

The  properties  of  earth  with  respect  to  adhesion  and  friction 
are  so  variable  that  the  engineer  should  never  trust  to  tables  or  to 
information  obtained  from  books  to  guide  him  in  designing  earth- 
works, when  he  has  it  in  his  power  to  obtain  the  necessary  data 
either  by  observation  of  existing  earth-works  in  the  same  stratum 
or  by  experiment. 


EARTH-WORK.  427 


648.  Inclination  of  Side  Slopes. — The  proper  inclination  for  the 
side  slopes  of  cuttings  and  embankments  depends  on  the  nature  of 
the  soil  and  the  action  -of  the  atmosphere  and  of  internal  moisture 
upon  it. 

"  In  common  soils,  as  ordinary  garden  earth  formed  of  a  mixture 
of  clay  and  sand,  compact  clay,  and  compact  stony  soils,  although 
the  side  slopes  would  withstand  very  well  the  effects  of  the  weather 
with  a  steeper  inclination,  it  is  best  to  give  them  two  base  to  one 
perpendicular,  as  the  surface  of  the  roadway  will,  by  this  arrange- 
ment, be  well  exposed  to  the  action  of  the  sun  and  air,  which  will 
•cause  rapid  evaporation  of  the  moisture  of  the  surface.  Pure  sand 
and  gravel  may  require  a  greater  slope  according  to  circumstances. 
In  all  cases  where  the  depth  of  the  excavation  is  great  the  base  of 
the  slope  should  be  increased. 

"  In  excavations  through  solid  rock,  which  does  not  disintegrate 
on  exposure  to  the  atmosphere,  the  side  might  be  perpendicular; 
but  as  this  would  exclude  in  a  great  degree  the  action  of  the  sun 
and  air,  which  is  essential  to  keeping  the  road-surface  dry  and  in 
good  order,  it  is  necessary  to  make  the  side  slopes  with  an  inclina- 
tion varying  from  one  base  to  one  perpendicular,  to  one  base  to 
two  perpendicular,  or  even  greater,  according  to  the  locality;  the 
inclination  of  the  slopes  on  the  south  side  in  northern  latitudes 
being  the  greater,  to  expose  better  the  road-surface  to  the  sun-rays. 

"  The  slaty  rocks  generally  decompose  rapidly  on  the  surface 
when  exposed  to  moisture  and  the  action  of  frost.  The  side 
slopes  in  rocks  of  this  character  may  be  cut  into  steps  and  then  be 
covered  by  a  layer  of  vegetable  mould  sown  in  grass-seed,  or  else 
the  earth  may  be  sodded  in  the  usual  way." 

649.  Form  of  Side  Slopes. — The  natural,  strongest,  and  ultimate 
form  of  earth  slopes  is  a  concave  curve,  in  which  the  flattest  portion 
is  at  the  bottom.     This  form  is  very  rarely  given  to  the  slopes  in 
constructing  them ;  in  fact,  the  reverse  is  often  the  case,  the  slopes 
being  made  convex,  thus  saving  excavation  for  the  contractor  and 
inviting  slips. 

In  cuttings  exceeding  10  feet  in  depth  the  forming  of  concave 
slopes  will  materially  aid  in  preventing  slips,  and  in  any  case  they 
will  reduce  the  amount  of  material  which  will  eventually  have  to 
be  removed  when  cleaning  up.  Straight  or  convex  slopes  will  con- 
tinue to  slip  until  the  natural  form  is  attained. 


428 


HIGHWAY    CONSTRUCTION. 


A  revetment  or  retaining  wall  at  the  base  of  a  slope  will  save 
•excavation. 

In  excavations  of  considerable  depth,  and  particularly  in  soils 
liable  to  slips,  the  slope  may  be  formed  in  terraces,  the  horizontal 
offsets  or  benches  being  made  a  few  feet  in  width  with  a  ditch  on 
the  inner  side  to  receive  the  surface-water  from  the  portion  of  the 
side  slope  above  them.  These  benches  catch  and  retain  earth  that 
may  fall  from  the  slopes  above  them.  (See  Fig.  56.) 


FIG.  56.    HILLSIDE  ROADS. 

650.  Covering  of  Slopes. — It  is  not  usual  to  employ  any  artificial 
means  to  protect  the  surface  of  the  side  slopes  from  the  action  of 
the  weather;  but  it  is  a  precaution  which  in  the  end  will  save  much 
labor  and  expense  in '  keeping  the  roadways  in  good  order.     The 
simplest  means  which  can  be  used  for  this  purpose  consists  in  cov- 
ering the  slopes  with  good  sods,  or  else  with  a  layer  of  vegetable 
mould  about  four  inches  thick,  carefully  laid  and  sown  with  grass- 
seed.     These  means  are  amply  sufficient  to  protect  the  side  slopes 
from  injury  when  they  are  not  exposed  to  any  other  causes  of 
deterioration  than  the  wash  of  the  rain  and  the  action  of  frost  on 
the  ordinary  moisture  retained  by  the  soil. 

A  covering  of  brushwood  or  a  thatch  of  straw  may  also  be  used 
with  good  effect ;  but  from  their  perishable  nature  they  will  require 
frequent  renewal  and  repairs. 

"  Where  stone  is  abundant  a  small  wall  of  dry  stone  may  be 
constructed  at  the  foot  of  the  slopes  to  prevent  any  wash  from  them 
being  carried  into  the  ditches." 

651.  Slips. — "The  stratified  soils  and  rocks  in  which  the  strata 
have  a  dip  or  inclination  to  the  horizon  are  liable  to  slips,  or  to 
give  way  by  one  stratum  becoming  detached  and  sliding  on  another, 


EAKTH-WORK.  429 


which  is  caused  either  from  the  action  of  frost  or  from  the  pres- 
sure of  water  which  insinuates  itself  between  the  strata.  The 
worst  soils  of  this  character  are  those  formed  of  alternate  strata  of 
clay  and  sand,  particularly  if  the  clay  is  of  a  nature  to  become 
semi-fluid  when  mixed  with  water.  The  best  preventives  that 
can  be  resorted  to  in  these  cases  are  to  adopt  a  system  of  thorough 
drainage,  to  prevent  the  surface-water  of  the  ground  from  running 
down  the  side  slopes,  and  to  cut  off  all  springs  which  run  towards 
the  roadway  from  the  side  slopes.  The  surface-water  may  be  cut 
off  by  means  of  a  single  ditch,  termed  a  catch-water  ditch,  exca- 
vated a  few  feet  back  from  the  crest  of  the  slope,  so  that  it  inter- 
cepts the  water  before  it  reaches  the  slope  of  the  excavation,  and 
convey  it  off  to  the  most  convenient  natural  water-courses.  Usu- 
ally this  ditch  will  be  required  only  on  the  up-hill  side  of  the  road ; 
for  in  almost  every  case  it  will  be  found  that  the  side  slope  on  the 
down-hill  side  is,  comparatively  speaking,  but  slightly  affected  by 
the  surface-water. 

"Where  slips  occur -from  the  action  of  springs,  it  frequently 
becomes  a  very  difficult  task  to  secure  the  side  slopes.  If  the 
sources  can  be  easily  reached  by  excavating  into  the  side  slopes, 
drains  formed  of  layers  of  fascines  or  brushwood  may  be  placed  to 
give  an  outlet  to  the  water  and  prevent  its  action  upon  the  side 
slopes.  The  fascines  may  be  covered  on  top  with  good  sods  laid 
with  the  grass  side  beneath,  and  the  excavation  made  to  place  the 
•drain  filled  in  with  good  earth  well  rammed.  Drains  formed 
of  broken  stone  or  cobbles  covered  in  like  manner  on  top  with  a 
layer  of  sod  to  prevent  the  drain  from  becoming  choked  with  earth 
may  be  used  under  the  same  circumstances  as  fascine  drains. 
Where  the  sources  are  not  isolated  and  the  whole  mass  of  the  soil 
forming  the  side  slopes  appears  saturated,  the  drainage  may  be 
effected  by  excavating  trenches  a  few  feet  wide  at  short  intervals 
to  the  depth  of  some  feet  into  the  side  slopes,  and  filling  them  with 
boulders  or  broken  stone,  or  else  a  general  drain  of  stone  may  be 
made  throughout  the  whole  extent  of  the  side  slope  by  excavating 
into  it.  When  this  is  deemed  necessary  it  will  be  well  to  arrange 
the  drain  like  an  inclined  retaining-wall  with  buttresses  at  inter- 
vals projecting  into  the  earth  farther  than  the  general  mass  of  the 
drain.  The  front  face  of  the  drain  should,  in  this  case,  also  be 
covered  with  a  layer  of  sods  with  the  grass  side  next  to  the  stones 


430 


HIGHWAY   CONSTRUCTION-. 


forming  the  drain,  and  upon  this  a  layer  of  good  earth  should  be- 
compactly  laid  to  form  the  face  of  the  side  slopes.  The  drain  need 
only  be  carried  high  enough  above  the  toe  of  the  side  slope  to  tap 
all  the  sources,  and  it  should  be  sunk  sufficiently  below  the  roadway 
to  give  it  a  secure  footing." 

"The  drainage  has  been  effected,  in  some  cases,  by  sinking 
wells  or  shafts  at  some  distance  behind  the  side  slopes,  from  the 
top  surface  to  the  level  of  the  bottom  of  the  excavation  and  lead- 
ing the  water  which  collects  in  them  by  pipes  into  the  drains  at 
the  foot  of  the  side  slopes.  In  others  a  narrow  trench  has  been 
excavated,  parallel  to  the  axis  of  the  road,  from  the  top  surface  ta 
a  sufficient  depth  to  tap  all  the  sources  which  flow  towards  the- 
side  slope,  and  a  drain  formed  either  by  filling  the  trench  wholly 
with  stone  or  else  by  arranging  an  open  conduit  at  the  bottom  to 
receive  the  water  collected,  over  which  a  layer  of  brushwood  is- 
iaid,  the  remainder  of  the  trench  being  filled  with  stone." 

652.  Embankments. — The  best  materials  for  embankments  are 
those  whose  frictional  stability  is  the  greatest  and  the  most  perma- 
nent, such  as  fragments  oi  rock,  shingle,  gravel,  and  clean  sand. 
Clay  forms  safe  embankments,  provided  it  is  dry,  or  nearly  dry, 
when  laid  down.     Wet  clay,  vegetable  mould,  and  mud  are  unfit  for 
use  in  embankments;  so  also  is  peat,  except  when  dry. 

653.  An  embankment  may  be  made  in  three  ways :  (1)  In  one 
layer.     (2)  In  two  or  more  thick  layers.     (3)  In  thin  layers. 

(1)  In  One  Layer. — This    being  the    cheapest    and    quickest 


FIG.  57. 

method  consistent  with  stability,  is  that  followed  in  all  earth-works  in. 
which  there  is  no  special  reason  requiring  it  to  be  performed  by  the 
other  methods.  In  Fig.  57  BAG  represents  the  natural  surface  of 


EAKTH-WORK.  431 


the  ground;  DA,  part  of  the  base  of  a  cutting;  AEC,  an  embank- 
ment the  construction  of  which  is  carried  forward  in  the  direction 
AE  of  its  full  width  and  height  (including  a  sufficient  allowance 
for  settlement),  by  running  dump-carts  on  temporary  tracks  from 
the  cutting  along  the  top  of  the  embankment,  and  tipping  them 
at  E,  so  that  the  earth  runs  down  and  spreads  itself  over  the  sloping 
end  EC  of  the  bank,  which  is  called  the  "tip."  Embankments 
formed  in  this  manner  are  deficient  in  compactness,  for  the  par- 
ticles of  earth  which  are  emptied  from  the  top  of  the  bank  will 
temporarily  stop  in  their  descent  at  the  point  of  the  slope  at  which 
the  friction  becomes  sufficient  to  balance  their  gravity;  and  when 
more  earth  comes  upon  them,  they  will  give  way  and  slide  lower 
down,  causing  the  portions  above  them  to  slip  and  crack,  and  thus 
delay  for  a  long  time  the  complete  consolidation. 

Tipping  or  dumping  the  earth  over  the  sides  of  banks  made  in 
the  above  manner  should  not  be  allowed,  for  the  earth  so  dumped 
is  liable  afterwards  to  slip  off. 

The  solidity  of  embankments  formed  in  the  above  manner  may 
be  increased  by  filling  from  the  sides  towards  the  centre  in  order 
that  the  earth  may  arrange  itself  in  layers  with  a  dip  from  the  sides 
inwards. 


FlG.  58.    CROSS-SECTION  OF  EARTH  EMBANKMENT, 
SHOWING  METHOD  OF  PLACING  THE  LAYERS. 

As  the  rapidity  with  which  a  bank  can  be  made  by  this  method 
is  dependent  upon  the  number  of  tipping  or  dumping  points,  it  is 
usual  to  form  the  bank  wider  at  top  and  narrower  at  the  bottom 
than  it  is  finally  to  be,  maintaining  of  course  the  requisite  area  ot 
cross-section;  the  excess  at  the  top  (the  angles  AB,  Fig.  59)  be- 
ing subsequently  moved  down  to  the  bottom,  thus  securing  the 
required  width  of  base  and  inclination  of  side  slopes. 

It  is  mistaken  economy  to  first  form  embankments  narrow  and 


432  HIGHWAY    CONSTRUCTION-. 

afterwards  widen  them  by  lateral  additions,  for  the  new  material 
will  never  unite  perfectly  with  the  old. 

(2)  In  Thick  Layers. — This  process  has  been  used  in  some  em- 
bankments of  great  height.  It  consists  in  completing  the  con- 
struction of  the  embankment  up  to  a  certain  height  by  the  process 
of  end-dumping  already  described;  leaving  that  layer  for  a  time 
to  settle,  and  then  making  a  second  layer  in  the  same  way,  and  so 


FIG.  59. 

on.  It  involves  much  additional  time  and  labor,  and  is  seldom 
employed.  It  is,  however,  useful  in  making  embankments  of  hard 
olay  or  shale,  which,  when  first  dumped,  consists  of  angular  lumps 
that  lie  with  vacant  spaces  between  them  and  do  not  form  a  com- 
pact mass  until  partially  softened  and  broken  down  by  the  action 
of  air  and  moisture. 

(3)  In  Thin  Layers. — This  process  consists  in  spreading  the 
earth  in  horizontal  layers  of  from  9  to  18  inches  deep,  and  rolling 
or  ramming  each  layer  so  as  to  make  it  compact  and  firm  before 
laying  down  the  next  layer.  Being  a  tedious  and  costly  process, 
it  is  used  in  special  cases  only,  of  which  the  principal  are  the  filling 
in  behind  retaining  walls,  behind  wings  and  abutments  of  bridges 
and  culverts,  and  over  their  arches. 

654.  Side  Slopes  of  Embankments. — In  forming  the  embank- 
ments the  side  slopes  should  be  made  with  a  greater  inclination 
than  that  which  the  earth  naturally  assumes,  for  the  purpose  of 
giving  them  greater  durability,  and  to  prevent  the  width  of  the 
top  surface  along  which  the  roadway  is  made  from  diminishing  by 
every  change  in  the  side  slopes,  as  it  would  were  they  made  with 
the  natural  slope.  To  protect  the  side  slopes  more  eifectually 
they  should  be  sodded,  or  sown  in  grass-seed,  and  the  surface  water 
of  the  top  should  not  be  allowed  to  run  down  them,  as  it  would 
soon  wash  them  into  gulleys  and  destroy  the  embankment.  In 


EARTH-WOKK.  433 


localities  where  stone  is  plentiful  a  sustaining  wall  of  dry  stone 
may  be  advantageously  substituted  for  the  side  slopes. 

The  toe  or  foot  of  embankments  has  a  tendency  to  spread ;  this 
may  be  resisted  by  excavating  a  small  trench  along  the  toe,  or  by 
buttressing  with  a  low  stone  wall. 

655.  Drainage  of  Embankments. — The  only  drains  required  for 
embankments  over  good  ground  are  the  ordinary  side  ditches,  with 
occasional  culverts  to  convey  the  water  from  them  into  the  natural 
water-courses.     When  springs  are  crossed,  stone  drains  or  culverts 
may  be  built  to  carry  the  water  clear  of  the  embankment. 

656.  Embankments  over  Plains. — When  a  roadway  is  carried 
across  an  extensive  plain,  it  is  almost  always  necessary,  in  order  to 
keep  its  surface  dry,  that  it  should  be  raised  above  the  general 
level  of  the  ground;  and  where  inundations  occur,  the  requisite 
height  may  be  considerable.     In  Fig.  60,  A  represents  a  cross-sec- 


//m/f/)///^^ 

FIG.  60.    SECTION  OF  EMBANKMENTS  OVER  PLAINS. 

iion  of  an  embankment  for  this  purpose,  the  materials  for  which 
.are  obtained  by  digging  a  pair  of  trenches  alongside  of  it.  These 
trenches,  by  collecting  surface-water  and  discharging  it  into  the 
nearest  river  or  other  main  drainage  channel,  tend  to  shorten  the 
duration  of  floods  in  the  neighborhood  of  the  line. 

657.  Embankments  across  Marshes. — When  the  ground  is  so 
soft  that  an  embankment  made  in  the  ordinary  way  would  sink  in 
it,  different  expedients  are  to  be  employed  according  to  the  kind 
-and  degree  of  difficulty  to  be  overcome.  The  following  list  of 
expedients  is  arranged  in  the  order  of  an  increasing  scale  of  dif- 
ficulty : 

(1)  By  digging  side  drains  parallel  to  the  site  of  the  intended 
embankment,  the  firmness  of  the  natural  ground  may  be  increased. 

(2)  If  the  material  of  the  natural  ground  has  a  definite  angle 
of  repose,  though  much  flatter  than  that  of  the  material  of  the 
embankment,  the  slopes  of  the  embankment  may  be  formed  to  the 
same  angle,  thus  giving  it  a  broader  foundation  than  it  would  have 
with  its  own  natural  slope. 


434  HIGHWAY   CONSTRUCTION. 

(3)  A  foundation  may  be  made  for  the  embankment  by  digging 
a  trench  and  filling  it  with  a  stable  material. 

(4)  The  ground  may  be  compressed  and  consolidated  by  driving 
short  piles. 

(5)  The  embankment  may  be  made  of  materials  light  enough 
to  form  a  sort  of  raft,  floating  on  the  soft  ground,  such  as  hurdles, 
fascines,  timber  platforms,  or  dry  peat.     Dry  peat  was  the  material 
used  by  George  Stephenson  to  carry  the  Liverpool  and  Manchester 
Railway  across  Chat  Moss.     Its  heaviness,  when  well  dried  in  the 
air,  is  about  30  pounds  per  cubic  foot;  and  when  saturated  with 
water,  63  pounds.     On   the    dry-peat  embankment  was  placed  a 
platform  of  two  layers  of  hurdles  to  carry  the  ballast. 

(6)  Should  all  other  expedients  fail,  a  marsh  or  bog  may  still 
be  crossed  by  throwing  in  stones   or  gravel   and  sand,  until  an 
embankment  is  formed  resting  on  the  hard  stratum  below,  and 
with  its  top  rising  to  the  required  level.     It  is  found  that  the 
material  of  the  embankment  assumes  the  same  natural  slope  that 
it  would  do  in  the  air. 

Mr.  George  W.  Waite,  C.E.,  gives  the  following  description  of  a 
road  constructed  by  him  in  1868  in  the  village  of  Hyde  Park  (now 
in  the  city  of  Chicago) : 

"  The  line  crossed  a  marsh  about  one  mile  wide  which  extended 
from  about  two  miles  west,  easterly  to  Lake  Michigan,  and  south- 
easterly to  Calumet  River,  a  distance  of  two  miles,  and  was  at  that 
time  all  covered  with  water  from  a  few  inches  to  two  feet  deep.. 
Wild  rice  grew  all  over  that  portion  of  the  marsh,  about  8  feet, 
high,  and  the  stalks  were  from  i  to  £  inch  in  diameter  at  the 
bottom.  Through  the  central  portion  of  the  marsh  was  an  open 
water-way  about  10  feet  wide  in  the  channel  proper,  with  no  per- 
ceptible current,  which  widened  out  into  small  lakes  every  few 
hundred  feet. 

"  The  channel  and  lakes  had  from  3  to  4  feet  of  water  and  about 
the  same  depth  of  black  slush  or  decayed  vegetable  matter. 

"  Soundings  showed  the  turf  to  be  about  1  foot  thick,  with  from 
2  to  6  feet  of  soft  black  vegetable  mould  underneath,  then  a  hard 
bottom  of  blue  clay. 

"  The  method  of  construction  was  as  follows :  Beginnirg  afc  the 
dry  ground  on  the  south  end,  an  18-foot  inch  board,  1  foot  wide, 
was  placed  lengthwise  on  the  outside,  9  feet  from  the  centre,  then. 


EARTH- WORK.  435 


one  in  the  centre,  6  feet  in  advance  of  the  first,  and  then  one  ort 
the  opposite  side,  6  feet  in  advance  of  the  middle  one.  Then  the 
three  pieces  laid  lengthwise  were  covered  with  18-foot  sound  boards- 
1  inch  thick,  laid  crosswise  and  nailed  as  fast  as  laid  to  keep  them 
in  their  places.  On  these  were  placed  three  more,  lengthwise  as  at 
first,  one  in  the  centre  and  one  on  each  side,  and  these  were  nailed 
through  into  the  under  ones.  Next  all  the  wild  rice  for  a  space  of 
about  75  feet  on  each  side  was  cut  down  and  pitched  with  forks 
onto  the  floating  platform  or  roadbed.  It  made  a  compact  cover- 
ing about  2  feet  thick.  At  the  end  of  the  first  500  feet  a  turn- 
around for  teams  on  one  side  was  made  of  boards  doubled,  36  feet 
square,  thoroughly  nailed. 

"  Then  the  whole  500  feet  of  roadbed  was  covered  16  feet  wide 
with  about  15  inches  thick  of  stone,  and  on  this  was  placed  3 
inches  of  crushed  stone. 

"  After  finishing  the  first  500  feet  the  turn-around  was  removed 
to  the  end  of  the  second  500  feet,  and  so  on  to  completion.  Near 
the  middle  of  the  marsh  was  a  lake  which  the  line  crossed,  some 
200  feet  wide.  This  was  covered  with  a  bent  bridge  50  feet  long, 
and  the  balance  with  floats,  the  same  as  the  marsh  but  wider.  The 
bridge  was  placed  on  the  pond-lily  roots  that  everywhere  abounded 
in  the  bottom  of  all  these  small  lakes,  and  left  about  2  feet  higher 
than  needed  to  allow  for  settling,  but  it  has  not  yet  settled  more 
than  some  6  inches,  although  a  pole  can  be  run  down  between  the 
network  of  roots  and  into  the  slush  underneath  about  3  feet  below 
the  bottom  of  the  sills  before  the  hard  bottom  is  reached. 

"  The  road  settled  on  an  average  about  2  feet,  with  the  excep- 
tion of  two  or  three  short  distances  where  it  settled  3  feet,  but  it 
did  not  break  through  the  turf  in  any  place.  At  a  high  stage  of 
water  some  places  for  a  few  feet  in  length  would  be  1  foot  under 
water. 

"  The  road  has  stood  over  23  years  and  has  been  considerably 
travelled,  and  is  in  good  condition  at  the  present  time  (1892).  It 
has  had  but  very  little  top-dressing  during  the  whole  time.  Sine^ 
the  road  was  constructed  the  marsh  has  nearly  all  been  drained 
and  has  mostly  become  solid,  and  the  land  in  it,  which  at  that  time 
was  not  worth  $25.00  per  acre,  has  just  been  sold  for  $2500.00  per 
acre." 

658.  Embankments  across  Bogs. — Undrained  moss  consists  of 


436  HIGHWAY    CONSTHUCTIOtf. 

about  90  per  cent  of  water  and  10  per  cent  of  vegetable  matter,  and 
consequently  while  in  that  condition  it  is  quite  incapable  of  sus- 
taining a  roadway;  but  in  most  cases  the  surface  of  the  underlying 
solid  ground  is  above  the  level  of  the  waterways  of  the  district, 
and  by  gradual  drainage  the  fluid  mass  may  be  condensed  into  a 
more  or  less  solid  peat.  The  drainage  should  not  be  effected  at  too 
rapid  a  rate,  as  there  is  a  liability  of  the  escaping  water  carrying  off 
with  it  the  particles  of  vegetable  matter,  causing  the  sides  of  the 
ditches  to  collapse,  and  producing  fissures  on  the  surface  of  the 
moss  which,  becoming  filled  with  water  or  ice,  extend  more  and 
more. 

The  drainage  of  the  strip  of  moss  along  the  site  of  the  intended 
roadway  should  be  effected  by  side  drains,  carried  gradually  down 
and  into  the  solid  underlying  ground.  And  if  this  can  be  done,  it' 
is  probable  that  the  moss  by  conversion  into  peat  will  be  reduced 
by  about  one  third  of  its  total  thickness.  The  sides  of  the  drains, 
instead  of  being  sloped,  should  be  cut  in  a  series  of  steps  or  benches, 
each  of  about  three  feet  deep  and  three  feet  broad,  down  to  the  re- 
quisite level,  so  as  to  expose  as  large  a  surface  as  possible  to  the 
influence  of  wind  and  sun,  and  thereby  produce  a  comparatively 
hard  skin  of  peat,  and  consequently  lessen  the  destructive  action 
of  frost. 

The  side  ditches  should  be  cut  parallel  to  the  axis  of  the  road- 
way and  at  a  distance  from  the  centre  line  on  each  side  of  30  or 
more  feet,  depending  upon  the  width  of  the  berm  intended  to  be 
left  between  th  eedge  of  the  roadway  and  the  side  ditch.  The  berm 
should  not  be  less  than  six  feet.  Transverse  drains  should  be  cut 
at  right  angles  to  the  side  drains,  and  at  distances  apart  not  exceed- 
ing 30  feet.  These  transverse  drains  should  extend  across  and 
beyond  the  side  drains  from  50  to  100  feet.  The  material  exca- 
vated from  these  drains  should  not  be  deposited  near  their  edges,  or 
slips  will  probably  occur;  it  may  be  spread  on  the  roadway  site. 
After  the  draining  is  completed,  the  roadway  may  be  formed  of 
sand  and  surfaced  with  broken  stone. 

659.  Embankments  on  Hillsides. — When  the  axis  of  the  road- 
way is  laid  out  on  the  side  slope  of  a  hill,  and  the  road  is  formed 
partly  by  excavating  and  partly  by  embanking,  the  usual  and  most 
simple  method  is  to  extend  out  the  embankment  gradually  along 
the  whole  line  of  the  excavation.  This  method  is  insecure  ;  the 


EABTH-WORK. 


437 


excavated  material  if  simply  deposited  on  the  natural  slope  is  liable 
to  slip,  and  no  pains  should  be  spared  to  give  it  a  secure  hold,  par- 
ticularly at  the  toe  of  the  slope.  The  natural  surface  of  the  slopo 


D 


ON 


FIG.    61,    SHOWING 


METHOD   OF  CONSTRUCTION 
HILLSIDES. 


should  be  cut  into  steps  as  shown  in  Figs.  61,  62.  The  dotted 
line  AB  represents  the  natural  surface  of  the  ground,  CEB  the 
excavation,  and  ADC  the  embankment,  resting  on  steps  which 
have  been  cut  between  A  and  0.  The  best  position  for  these  steps 
is  perpendicular  to  the  axis  of  greatest  pressure.  If  AD  is  inclined 

A 


FIG.  62.     SHOWING 


METHOD   OF  CONSTRUCTION 
HILLSIDES. 


ON 


at  the  angle  of  repose  of  the  material,  the  steps  near  A  should  be 
inclined  in  the  opposite  direction  to  AD,  and  at  an  angle  of  nearly 


438  HIGHWAY   CONSTRUCTION. 

90  degrees  thereto,  while  the  steps  near  0  may  be  level.  If  stone  is 
abundant,  the  toe  of  the  slope  may  be  further  secured  by  a  dry  wall 
of  stone. 

On  side  hills  of  great  inclination  the  above  method  of  construc- 
tion will  not  be  sufficiently  secure;  retaining- walls  of  stone  must 
be  substituted  for  the  side  slopes  of  both  the  excavations  and  em- 
bankments. These  walls  may  be  made  of  stone  laid  dry,  when 
stone  can  be  procured  in  I  locks  of  sufficient  size  to  render  this 
Mnd  of  construction  of  sufficient  stability  to  resist  the  pressure  of 
the  earth.  But  when  the  blocks  of  stone  do  not  offer  this  security, 
they  must  be  laid  in  mortar.  The  wall  which  forms  the  slope  of 
the  excavation  should  be  -carried  up  as  high  as  the  natural  surface 
of  the  ground.  Unless  the  material  is  such  that  the  slope  may  be 
safely  formed  into  steps  or  benches  as  shown  in  Figs.  61  and  62,  the 
wall  that  sustains  the  embankment  should  be  built  up  to  the  surface 
of  the  roadway,  and  a  parapet  wall  or  fence  raised  upon  it,  to  pro- 
tect pedestrians  against  accident.  (See  Figs.  56  and  63.) 

660.    Roadways  on    Rock-slopes. — On    rock-slopes  when    the 
inclination  of  the  natural  surface  is  not  greater  than  one  perpen 
dicular  to  two  base,  the  road  may  be  constructed  partly  in  excava- 
tion and  partly  in  embankment  in  the  usual  manner  or,  as  shown 
in  Figs.  63,  64,  65,  by  cutting  the  face  of  the  slope  into  horizontal 


63.    SHOWING    METHOD    OF   CONSTRUCTION    ON 
HILLSIDES. 

steps  with  vertical  faces,  and  building  up  the  embankment  in  the 
form  of  a  solid  stone  wall  in  horizontal  courses,  either  dry  or  laid 
in  mortar.  Care  is  required  in  proportionin  g  the  steps,  as  all  attempts 


EAKTH-WORK.  439 


to  lessen  the  quantity  of  excavation  by  increasing  the  number  and 
diminishing  the  width  of  the  steps  require  additional  precautions 
against  settlement  in  the  build-up  portion  of  the  roadway. 


FIG.  64,     SHOWING    METHOD   OF  CONSTRUCTION   ON 

HILLSIDES. 

When  the  rock-slope  has  a  greater  inclination  than  \ :  2  the 
whole  of  the  roadway  should  be  in  excavation. 

In  some  localities  roads  have  been  constructed  along  the  face  of 
nearly  perpendicular  cliffs  on  timber  frameworks  consisting  of  hori- 
zontal beams,  firmly  fixed  at  one  end  by  being  let  into  holes  drilled 
in  the  rock,  the  other  end  being  supported  by  an  inclined  strut  which 
rests  against  the  rock  in  a  shoulder  cut  to  receive  it.  There  are 
also  examples  of  similar  platforms  suspended  instead  of  being  sup- 
.  ported. 

661.  The  vertical  faces  of  rock-cliffs  present  the  most  formida- 
ble obstacles  to  the  formation  of  roads.  When  the  rock  is  suffi- 
ciently hard  and  not  liable  to  early  disintegration  a  half-tunnel  like 
DEF,  Fig.  66,  may  be  formed  by  blasting;  but  if  it  be  too  soft  and 
rotten  to  admit  of  this  being  done,  the  best  plan,  if  the  cliff  be  of 
any  great  height  BE  above  the  formation  level,  is  to  blow  out  the 
whole  piece  GEF  by  a  large  mine  at  E.  Mining  should  not,  as  a 
rule,  be  employed  where  there  is  a  chance  of  the  strata  being  blown 
out  downwards  according  to  the  dip,  for  a  piece  may  be  blown  out, 
like  the  shaded  portion  Fig.  67,  when  much  time  and  expense  are 
entailed  in  rectifying  the  level. 

The  general  mode  of  attacking  a  vertical  cliff  and  of  forming  a 
half-tunnel  is  shown  in  Fig.  68.  The  large  blasts,  a,  a,  a,  a,  driven 
8  feet  in  depth,  at  an  angle  of  45  degrees,  are  7  feet  3  inches  apart 
horizontally  and  5  feet  vertically.  The  small  holes,  b,  b,  etc.,  3  feet 


440 


HIGHWAY   CONSTRUCTION-. 


EXAMPLES  OF  ROADS  ON  ROCK  SLOPES, 


Tig  6  5 


Fig  66. 


Fig.  67. 


A       l_"U 


II,  ,  f. 


a     a 


.    . 

"        ''«,u?,^      «      •      \ 

°      V  •   *  ;,  •  £ 


a,   a      ce 


rig.68. 


EARTH- WORK.  441 


apart  and  3  feet  deep,  which  are  not  fired,  serve  to  determine  and 
facilitate  rupture  at  the  proper  level.  These  blasts,  when  fired, 
generally  blow  out  or  loosen  a  piece  like  ABCD.  The  remaining 
space,  BEF,  is  blown  out  in  the  same  manner. 

662.  Rock  Excavation. — Excavation  in  hard  rock  is  usually  per. 
formed  by  means  of  some  explosive  material  inserted  in  a  hole 
bored  in  the  rock,  and  when  ignited  it  loosens  the  mass  and  permits 
of  its  being  broken  up  into  pieces  of  the  required  size. 

The  diameter  and  depth  of  the  hole  vary  with  the  quantity  of 
rock  to  be  loosened  at  each  blast,  and  also  with  the  strength  of  the 
explosive  used. 

The  quantity  of  rock  loosened,  other  conditions  being  the  same, 
is  roughly  proportional  to  the  cube  of  the  "  line  of  least  resistance/' 
which  is  generally  the  shortest  distance  from  the  centre  of  the 
charge  to  the  surface  of  the  rock. 

If  E  =  the  quantity  of  the  explosive  in  pounds,  and 
L  =  the  line  of  least  resistance  in  feet,  then 

E=  CV\ 

C  =  .032  blasting  powder; 

=  .005        "        cotton; 

=  .003  nitroglycerine  or  dynamite. 

Ordinary  blasting  powder,  1  pound  of  which  occupies  about  30 
cubic  inches,  is  ignited  by  means  of  a  fuse,  which  burns  at  the  rate 
of  about  2  feet  per  minute,  varying  slightly  with  each  coil. 

In  estimating  it  is  usual  to  allow  f  of  a  pound  of  powder  to  each 
cubic  yard  of  solid  rock.  The  actual  quantity  required  will  vary 
with  the  nature  of  the  rock  and  its  degree  of  compactness  or  loose- 
ness, the  latter  requiring  most  powder. 

Dynamite  and  nitroglycerine  should  be  fired  by  percussion. 
Detonating  tubes  or  caps  are  made  for  the  purpose,  which  explode 
on  being  ignited  either  by  an  ordinary  fuze  or  by  a  galvanic  battery. 

663.  Blasting. 

If  L  =  least  line  of  resistance  in  feet ; 

X  =  number  of  ounces  of  powder  required  to  blast  any  rock 

when  L  —  2  feet; 
P  =  quantity  of  powder  in  ounces  required, — then 


442 


HIGHWAY   CONSTRUCTION 


or,  when  X  =  4  ounces, 


L  should  not  exceed  one  half  the  depth  of  hole. 

TABLE  LXVIL 
AMOUNT  OP  CHARGE  WHEN  X  =  4  OUNCES. 


L 

Charge  of  Powder. 

L 

Charge  of  Powder. 

feet. 

Ibs.         oz. 

feet. 

Ibs.         oz. 

1 

0          1 

5 

3          14| 

2 

0          4 

6 

6         12 

3 

0        13£ 

8 

16          0 

4 

2          0 

In  small  blasts  one  pound  of  powder  will  loosen  about  4|  tons. 
In  large  blasts  one  pound  of  powder  will  loosen  about  2f  tons. 
Thirty  cubic  inches  of  powder  weigh  one   pound.     Hence  we 
have  the  following  table,  showing  the  capacity  of  drill-holes : 


TABLE  LXVIII. 
CAPACITY  OF  DRILL-HOLES. 


Diameter 
of  Hole  in 
inches. 

Area  in  square 
inches. 

Ounces  of 
Powder  in  one 
inch  deep. 

Powder  in  one 
foot  deep. 

Depth  of  hole  in 
inches  to  contain 
one  Ib.  of  Powder. 

1 

0.7854 

0.419 

Ibs.      oz. 
0     5.028 

38.197 

H 

1.7671 

0.942 

0  11.300 

16.976 

2 

3.1416 

1.676 

1     4.112 

9  .  549 

2* 

4.9087 

2.618 

1  15.416 

6.112 

3 

7.0686 

3.770 

2  13.240 

4  244 

664.  In  blasting  no  loud  report  should  be  heard  nor  stones  bo 
thrown  out.  The  best  effect  is  produced  when  the  report  is  trifling. 
and  when  the  mass  is  lifted  and  thoroughly  fractured  without  the 
projection  of  fragments.  If  the  rock  be  only  shaken  by  a  blast 
and  not  moved  outward,  a  second  charge  in  the  same  hole  will  be 
very  effective. 


EAKTII-WORK.  443 


Any  kind  of  compact  brush,  such  as  pine  or  cedar  boughs,  laid 
on  rocks  about  to  be  blasted,  will  almost  completely  prevent  the 
flying  of  fragments,  and  thus  lessen  the  danger  to  persons  and 
buildings  in  the  vicinity. 

So  much,  however,  depends  upon  the  character  of  the  rock  to  be 
excavated,  whether  it  is  hard  or  soft,  stratified  or  unstratified,  and 
whether  the  position  of  the  excavation  allows  of  arranging  the  drill- 
holes in  the  most  advantageous  manner,  that  the  above  figures  must 
be  regarded  as  only  approximately  correct. 

665.  Holes  for  blasting  rock  are  bored  either  by  hand  or  machine 
•drills.    Shallow  cuts,  loose  boulders,  etc.,  are  more  cheaply  bored  by 
hand,  but  deep  and  extensive  cuttings  are  more  economically  car- 
ried out  by  the  use  of  machine  drills  operated  either  by  steam  or 
compressed  air. 

666.  Hand-drilling. — The  speed  with  which  holes  may  be  bored 
in  rock  varies  of  course  with  the  hardness  of  the  rock  and  the 
diameter  of  the  hole.     The  smaller  the  diameter  of  the  hole  the 
greater  the  depth  that  can  be  bored  in  a  given  time ;  and  the  depth 
will  be  greater  in  proportion  than  the  decrease  of  the  diameter. 

The  average  rate  of  progress  made  by  a  good  drillman  working 
a  churn-drill  in  granite  and  the  harder  rocks  is  about  as  follows  : 

Diam.  of  Drill.  Depth  bored  per  hour. 

Inches.  Inches. 

3 4 

2i 5 

2* 6 

.2 , 8 

If 10 

When  the  hole  exceeds  four  feet  in  depth  two  men  are  required 
to  operate  the  drill. 

667.  Machine-drilling. — Machine  drills  bore  holes  from  f  to  6 
inches  in  diameter.     The  rate  of  progress  is  controlled  by  the  same 
conditions  as  hand-drilling,  and  ranges  from  three  to  ten  feet  per 
hour,  depending  on  the  character  of  the  rock  and  the  size  of  the 
machine. 

668.  Cost  of  Rock  Excavation. — The  cost  of  simply  excavating 
rock  is  from   four  to  six  times  that  of  earth,  and  is  largely  con- 
trolled by  the  skill  of  the  overseer,  especially  as  regards  carrying  the 
excavation  to  its  full  depth.    If  this  is  not  done,  the  amount  left  in 


441  HIGHWAY   CONSTRUCTION. 

the  bottom,  especially  if  it  is  of  little  depth,  will  cost  several  times 
more  per  yard  to  remove  it  than  the  cost  per  yard  of  the  main  cut. 

669.  Earth  Excavation — Loosening  the  Earth. — The  loosening 
of  the  material  in  shallow  cuttings  and  in  light  soils  is  done  best 
by  the  plough,  and  its  removal  is  economically  executed  with  drag  or 
wheeled  scrapers.     Gravel,  clay,  and  hardpan  require  to  be  loosened 
by  the  pick,  or  if  the  depth  be  great,  explosives  may  be  employed. 

670.  Transport  of  Earth. — The  transport  of  earth  is  effected  in. 
the  following  ways  : 

(a)  Throwing  with  a  Shovel,  when  the  distance  horizontally 
does  not  exceed  12  feet  nor  vertically  6  feet. 

(b)  Wheelbarroivs  may  be  employed  running  upon  a  plank  for 
distances  up  to  200  feet. 

(c)  Carts. — Between  200  and  500  feet  two-wheeled  dump-carts 
may  be  used. 

(d)  Scrapers. — The  economical  limit  for  drag-scrapers  is  about 
150  feet.     Wheeled  scrapers  may  be  employed  up  to  500  feet. 

(e)  For  hauls  over  500  feet,  where  a  large  amount  of  work  is  to- 
be  done,  a  track  with  dump-cars  drawn  by  horses  will  be  found 
profitable. 

(/)  Dump-wagons. — The  dump-wagon  is  a  recent  invention;  it 
consists  of  a  four-wheeled  wagon,  the  body  of  which  turns  on  a 
horizontal  axle,  so  that  it  can  be  tipped  over  by  a  single  movement 
of  a  lever  and  the  earth  dumped  out.  Their  capacity  varies  from  35 
to  45  cubic  feet.  They  may  be  economically  employed  in  long 
hauls. 

The  distance,  however,  depends  much  upon  the  difficulty  of 
getting  out  the  earth.  With  hard  clay,  requiring  two  picks  to  a. 
shovel,  and  with  a  small  surface  to  work  upon,  two  carts  upon 
an  ordinary  road  will  take  away  all  that  a  dozen  men  can  get  out ;. 
while  with  an  easy  soil,  where  one  pick  will  keep  half  a  dozen 
shovels  busy,  a  larger  number  of  vehicles  will  be  required,  or  a 
quicker  haul,  which  may  be  obtained  by  putting  down  a  track. 
The  less  the  haul,  or  the  greater  the  speed  of  transport,  the 
fewer  may  be  the  number  of  vehicles  to  remove  a  given  amount 
of  material.  The  chief  point  to  be  gained  is  to  arrange  the  different 
classes  of  laborers  so  that  none  shall  be  kept  waiting.  Everything 
depends  upon  the  tact  for  management  possessed  by  the  overseer. 

671.  Loosening   and  Transporting  by  Machinery. — A  machine: 


EAKTH-WORK.  445 


•called  the  New  Era  Grader  (Fig.  211)  (Chap.  XXIII)  has  been 
developed  for  both  loosening  the  earth  and  automatically  transport- 
ing and  depositing  it  in  the  bank  when  the  material  is  obtained 
from  side  ditches,  as  in  the  case  of  building  a  bank  across  a  plain. 

The  machine  consists  of  a  plough  which  loosens  and  raises  the 
earth,  depositing  it  upon  a  transverse  carrying-belt,  which  conveys 
it  from  the  excavation  to  the  bank.  The  carrier-belt  is  of  heavy 
three-ply  rubber  3  feet  wide,  and  can  be  adjusted  to  deliver  the 
•earth  at  14,  17,  19,  or  22  feet  from  the  plough. 

The  machine  will  work  in  any  material  that  can  be  loosened 
Tvith  a  plough.  The  motive  power  is  horses,  usually  twelve  in 
number. 

The  capacity  of  the  machine  varies  from  100  to  150  cubic  yards 
per  hour,  depending  upon  the  resistance  of  the  material  to  be 
moved. 

The  number  of  attendants  required  to  operate  the  machine  is 
three.  The  cost  per  cubic  yard  loosened  and  placed  in  bank  will 
depend  upon  wages  and  team-hire.  With  wages  at  20  cents  per 
hour  for  laborers,  and  horsehire  at  10  cents  each  per  hour,  the  cost 
per  cubic  yard  would  be  1.80  cents. 

The  machine  can  also  be  used  to  excavate  material  in  deep  cuts. 
When  so  employed,  dump-wagons  are  used  to  transport  the  earth. 
The  carrier  of  the  machine  is  set  to  deliver  at  10  feet  ;  the  wagons 
are  driven  under  it  and  automatically  loaded  with  from  1 J  to  1£ 
yards  of  earth  in  from  20  to  30  seconds.  The  machine  can  thus 
load  from  60  to  80  wagons  per  hour. 

672.  Cost  of  Earth-work. — Regarding  the   cost   of  executing 
earthwork,  no  fixed  rules  can  be  given;  it  depends  largely  upon  the 
location,  kind  and  cost  of  labor,  and  character  of  the  management. 
In  general  it  ranges  from  10  to  35  cents  per  cubic  yard. 

The  several  items  that  go  to  make  up  the  total  cost  of  earth- 
work are  the  loosening  of  the  earth,  either  by  ploughs,  picks,  or 
-explosives,  the  loading,  it  into  the  barrows,  carts,  or  other  vehicles, 
the  moving  and  emptying  it,  the  spreading  it  out  upon  the  em- 
bankment, the  return  of  the  vehicle,  the  keeping  of  the  road  in 
order,  the  wear  and  tear  of  tools  and  vehicles,  the  interest  on  the 
cost  of  the  equipment,  the  wages  of  the  overseers,  and  the  contract- 
or's profit. 

673.  Haul. — The  cost  of  removing  excavated  material  when  the 


446  HIGHWAY   CONSTRUCTION. 

distance  does  not  exceed  a  certain  specified  limit  is  included  in  the 
price  per  cubic  yard  of  the  material  as  measured  in  the  cutting. 
But  when  the  material  must  be  carried  beyond  this  limit,  the  extra, 
distance  is  paid  for  at  a  stipulated  price  per  cubic  yard  per  100 
feet.  The  extra  distance  is  known  by  the  name  of  "  haul,"  and  is 
to  be  computed  by  the  engineer  with  respect  to  so  much  of  the 
material  as  is  affected  by  it. 

The  contractor  is  entitled  to  the  benefit  of  all  short  hauls  (less 
than  the  specified  limit),  and  material,  so  moved  should  not  be  aver- 
i iged  against  that  which  is  carried  beyond  the  limit.  Therefore,  in 
all  cuts  the  material  of  which  is  all  deposited  within  the  limiting 
distance,  no  calculation  of  haul  is  to  be  made. 

The  contractor  must  haul  free  that  portion  of  the  cutting  no 
one  yard  of  which  is  carried  beyond  the  specified  limit.  There- 
fore this  portion  is  first  to  be  determined  in  respect  to  its  extent, 
and  the  number  of  cubic  yards  contained  in  it  is  to  be  deducted 
from  the  total  content  of  the  cutting,  before  estimating  the  haul 
upon  the  remainder.  Find  on  the  profile  of  the  line  two  points, 
one  in  excavation  and  the  other  in  embankment,  such  that  while 
the  distance  between  them  equals  the  specified  limit,  the  included 
quantities  (allowing  for  shrinkage)  of  excavation  and  embankment 
shall  just  balance.  These  points  are  easily  found  by  trial  with  the 
aid  of  the  cross-sections  and  calculated  quantities,  and  become  the 
starting  points  from  which  the  haul  of  the  remainder  of  the 
material  is  to  be  estimated. 


B ^Y     i  D 


F(G.  69.    ILLUSTRATING  CALCULATION   OF  OVERHAUL. 

Fig.  69  represents  a  cut  and  fill  in  profile.  The  distance  AB  is 
the  limit  of  free  haul.  The  materials  taken  from  A  0  just  make 
the  fill  OB  and  without  charge  for  haul;  but  the  haul  for  every 
cubic  yard  taken  from  A  C  and  carried  to  the  fill  BD  is  subject 


EAIITH-WOKK.  447 


to  charge  for  the  distance  it  is  carried,  less  AB.  It  would  be 
impossible  to  find  the  distance  that  each  separate  yard  is  carried, 
but  we  know  from  mechanics  that  the  average  distance  for  the 
entire  number  of  yards  is  the  distance  between  the  centres  of 
gravity  of  the  cut  AC,  and  of  the  fill  BD,  which  is  made  from  it. 
If,  therefore,  X  and  Y  represent  the  centres  of  gravity,  the  actual 
average  haul  is  the  sum  of  the  distances  (AX  +  BY),  and  this 
(expressed  in  feet)  multiplied  by  the  number  of  cubic  yards  in  the 
cut  A  C  gives  the  product  to  which  the  price  for  haul  applies. 

If  a  cut  is  divided  and  parts  are  carried  in  opposite  directions, 
the  calculation  of  each  part  terminates  at  the  dividing  line.  If  a 
portion  of  the  material  in  AC  is  wasted,  it  must  be  deducted  and 
the  haul  calculated  on  the  remainder. 

The  specified  limit  is  sometimes  made  as  low  as  100  feet,  some- 
times as  high  as  1000  feet.  A  limit  of  about  300  feet,  however,  is 
usually  most  convenient,  as  it  includes  the  wheelbarrow  work  and 
a  large  part  of  the  carting,  while  it  protects  the  contractor  on  such 
long  hauls  as  may  occur. 

674.  Calculating  the  Amount  of  Earth-work. —The  quantity  of 
excavation  and  embankment  expressed  in  cubic  yards  is  required 
to  be  known,  in  order  to  compare  the  amount  of  work  to  be  done 
upon  the  different  trial  lines  which  may  have  been  surveyed.     For 
this  purpose  the  method  of  averaging  end  areas  is  sufficiently  exact; 
or  if  expedition  is  desired,  the  quantities  may  be  taken  from  any  of 
the  many  tables  of   quantities  which   for  level  cross-section  are 
reliable.     For  other  than  level  cross-section  the  tables  will  be  in 
error,  even  with  the  use  of  the  auxiliary  formula  given  with  them 
for  the  purpose  of  ascertaining  the  extra  amounts  to  be  added  for 
irregular  sections.     The  error  in  the  quantities  obtained  by  using 
the  tables  for  irregular  sections  will  be  of  no  practical  moment ;  in 
fact,  it  will  be  more  an  advantage  by  allowing  a  leeway  of  about 
3  or  4  per  cent  in  excess. 

675.  After  final  location  a  more  accurate  calculation  is  required, 
for  the  reason  that  the  contractors  who  usually  perform  the  work 
are  paid,  not  by  the  day,  nor  in  the  lump,  but  at  a  certain  price 
per  cubic   yard,   the   exact   determination  of  which   is   therefore 
required  to  ascertain  their  just  dues.     For  this  purpose  the  pris- 

•  moidal  formula  is  the  only  one  to  use.    It  is  as  follows :  To  the  sum 


448  HIGHWAY   CONSTRUCTION. 

of  the  end  areas  add  four  times  the  middle  area.     Multiply  the 
sum  by  one  sixth  of  the  length.    Divide  the  product  by  27. 

676.  Calculation  of  Half- widths  and  Areas. — The  boundaries  of 
a  piece  of  earth-work  in  general  are  as  follows : 

(1)  The  base,  or  subgrade  surface,  which  forms  the  bottom  of  a 
catting  or  the  top  of  an  embankment. 

(2)  The  original  surface  of  the  ground,  which  forms  the  top  of 
a  cutting  and  the  bottom  of  an  embankment. 

(3)  The   sides,  or    slopes,  which    connect   the  base  with   the 
natural  surface,  and  whose   inclination  is  the  steepest  consistent 
with  the  permanent  stability  of  the  material. 

677.  Examples    of  Cross-sections. — Figs.   70  to    76    represent 
examples  of  cross-sections  of  pieces  of  earth-work,  in  each  of  which 
DE  is  the  base,  AB  the  natural  surface,  and  DA  and  EB  are  the 
elopes.     In  Fig.  70  the  natural  surface  is  horizontal;  in  Figs.  73, 74, 
75,  76  it  slopes  sideways,  being  what  is  termed  "  side-long  ground." 
Figs.  71,  72  represent  forms  that  occasionally  occur.     Figs.  70  to  76 
represent  cuttings ;  to  represent  embankments  it  is  only  necessary 
to  conceive  them  to  be  turned  upside  down.     Figs.  75,  76  represent 
pieces  of  earth-work,  of  which  one  side,  CEB,  is  in  cutting  called 
"side  cutting"  and  the  other,  CD  A,  in  embankment. 

The  half-width  of  a  piece  of  earth-work  is  the  horizontal  dis- 
tance measured  at  right  angles  from  a  given  point  in  the  centre- 
line of  the  base  to  one  edge  of  the  cutting  or  embankment;  and 
although  it  is  called  "  half -width,"  it  is  very  generally  different  at 
opposite  sides  of  that  centre  line. 

Each  half-width  consists  of  two  parts :  the  real  half -width  of 
the  base,  which  is  fixed  by  the  design  of  the  work,  and  the 
horizontal  breadth  of  one  slope,  which  is  to  be  found  by  calculation 
or  by  drawing. 

In  each  of  the  figures  70  to  76,  C  represents  a  point  in  the 
centre-line,  as  marked  on  the  ground;  F,  the  point  vertically  above 
or  below  it  in  the  centre-line  of  the  base;  DG  and  EH  are  vertical 
lines  through  the  edges  of  the  base;  D F  and  FE  are  the  half- 
widths  of  the  base. 

In  Fig.  70,  where  the  ground  is  level  across,  GA  and  HB  are 
the  widths  of  the  slope,  and  GA  and  CB  the  half-v/idths  of  the 
earth-work. 

In  Figs.  74,  75,  and  76,  where  the  ground  slopes  sideways,  the 


EARTH -WORK. 


449 


EXAMPLES  OP  EARTH-WORK  CROSS-SECTIONS. 

A         6  C          H        B 


Fig.76, 


450  HIGHWAY   CONSTRUCTION. 

vertical  lines  through  D,  F,  and  E  are  produced,  if  necessary, 
and  are  cut  at  right  angles  by  horizontal  lines,  ALM  and  BNP, 
drawn  through  the  edges  of  the  earth-work.  AL  and  BN  are 
the  widths  of  the  slopes;  and  MA  and  PB  are  the  half-widths 
of  the  earth-work. 

When  the  natural  surface  of  the  ground  is  rugged,  the  best 
method  of  determining  the  widths  of  the  slopes  is  by  measure- 
ment upon  a  series  of  cross-sections  of  the  proposed  work 
plotted  to  the  same  scale  horizontally  and  vertically. 

678.  Calculation  of  Sectional  Areas  of  Earth-work.— The  com- 
putation of  the   areas  of  a  series  of   cross-sections  of  a  piece  of 
earth-work  is  necessary  to  ascertain  its  volume  or  cubical  quan- 
tity.    If  the  ground    is  rugged,  it  may  be  necessary  to  find  the 
area  of  each  cross-section  by  measurements  made  upon  a  drawing;  * 
but  if  the  ground  is  nearly  or  exactly  level  across,  or  has  nearly  or 
exactly  a  uniform  sidelong  slope,  the  area  of  a  given  cross-section 
can  be  computed  from  the  same  data  which  serve  to  compute  the 
width  of  the  slopes. 

679.  Formulas  for  the  Calculation  of  Areas. 


Fig.  70.  Area  =^-.(AB  +  DE). 

/"Y  777  T\  7/T 

Figs.  71,  72, 73.  Area  =  AB  .  -^j--  +  4~ . 

Fig.  74.  Area  =  J(cotan  X  -  cotan  F)2  -  DE\  K 

(For  values  of  JTsee  Table  LXIX.) 

*                                ( PR    I 
Fig.  75.  Area  of  the  larger  triangle  =- ; 

Fig.  75,  Area  of  the  smaller  triangle  = 


Fig.  76.  In  this  figure  C  and  F  coincide,  that  is,  there  is  neither 
cut  nor  fill,  the  triangles  are  similar,  and  the  area  is  expressed  by 
the  same  formula  given  for  Fig.  75. 


EARTH- WORK. 


451 


The  letters  on  Figs.  70  to  76  denote: 

L  =  angle  of  side  slopes  with  horizon. 
X  =  angle  of  natural  surface  with  horizon. 
S  =  ratio  of  slopes,  usually  1^  :  1. 

AG  or  HB    '  AB  -  DE 


S  =  cot  L  = 


CF 


AG  and  HB  =  CF .  S  =  OF .  cot  L. 


2CF 


TABLE  LXIX. 
VALUES  OP  K  FOR  DIFFERENT  SLOPES.    (G.  L.  MOLESWORTH.) 


Angle  of 


Values  of  K. 


Ground. 
X. 

Jtol. 

itol. 

Jtol.  v 

1  tol. 

H  to  l. 

10° 

.0922 

.0967 

.1016 

.107 

.1199 

12 

.1123 

.119 

.1265 

.1351 

.1562 

14 

.1329 

.1424 

.1533 

.1661 

.1992 

16 

.1543 

.1672 

.1794 

.2008 

.2512 

18 

.1766 

.1937 

.2145 

.2407 

.3164 

20 

.2 

.2222 

.25 

.2857 

.4009 

22 

.2252 

.2538 

.2907 

.3389 

.5128 

24 

.25 

.2857 

.3342 

.4012 

.6702 

26 

.2777 

.3225 

.3846 

.4761 

.909 

28 

.3067 

.362 

.4421 

.5675 

1.3123 

30 

.3373 

.4058 

.5091 

.6830 

2.1551 

32 

.3703 

.4545 

.5882 

.8333 

34 

.4058 

.5091 

.6830 

1.0373 

36 

.444 

.5707 

.7987 

1.3297 

38 

.4854 

.641 

.9434 

1.7857 

40 

.5307 

.7225 

1.131 

2.6041 

42 

.5807 

.8183 

1.385 

44 

.6364 

.9345 

1.754 

46 

.6983 

1.0729 

2.315 

48 

.7692 

1.25 

50 

.8488 

1.475 

Fig.  77  shows  a  profile  and  cross-sections  of  a  piece  of  earth- 
work. 

The  letters  denote : 

0  =  a  zero  point,  or  the  point  at  which  a  cutting  ends  and  an 

embankment  begins. 

L  =  the  distance  between  two  parallel  cross-sections. 
I  =  the  distance  from  a  cross-section  to  the  zero  point. 


452 


HIGHWAY    CONSTRUCTION. 


LJ 


o 


a: 

CO 


CO 


t 


CQ 


EARTH-WORK. 


453 


TAB.LE  LXX. 

(EARTH-  WORK.) 

CONTENTS  OF  I-FOOT  LENGTH  IN  CUBIC  FEET. 
(For  lengths  of  100  feet  move  decimal  two  places.) 


e 
1 

Central  Portion.  Base  in  feet. 

Contents  of  Both  Slopes. 

£ 

SS- 

t* 

& 

20 

30 

33  j  40 

50 

60 

66 

*:1 

i  :  1 

f  :1 

1  : 

H:l 

2:1 

3:1 

1 

2C 

30 

3£ 

4C 

50 

6C 

66 

.2 

.75 

1. 

I 

2 

40 

CO 

6C 

8C 

100 

120 

132 

1 

2' 

3 

6 

1$ 

2 

3 

60 

90 

9£ 

12C 

150 

180 

198 

2.2 

4. 

6.75 

13.o 

li 

2? 

3 

4 

80 

120 

13* 

160 

200 

240 

264 

4 

8 

12 

1 

24 

32 

4 

4 

5 

100 

150 

165 

200 

250 

300 

330 

6.25 

12.5 

18.75 

25 

37.5 

50 

7i 

5 

6 

120 

180 

198 

240 

300 

360 

396 

9 

18 

27 

36 

54 

72 

108 

& 

7 

140 

210 

231 

280 

350 

420 

462 

12.25 

24.5 

36.75 

49 

73.5 

98 

147 

7 

8 

160 

240 

264 

320 

400 

480 

528 

16 

32 

48 

64 

96 

128 

192 

8 

9 

180 

270 

297 

360 

450 

540 

594 

20.25 

40.5 

60.75 

81 

121.5 

162 

243 

9 

10 

200 

300 

330 

400 

500 

600 

660 

25 

50 

75 

100 

150 

200 

300 

10 

11 

220 

330 

363 

440 

550 

660 

726 

30.25 

60.5 

90.75 

121 

181.5 

242 

363 

11 

12 

240 

3601  396 

480 

600 

720 

792 

36 

72 

108 

144 

216 

288 

432 

12 

13 

260 

390 

429 

520 

650 

780 

858 

42.25 

84.5 

126.75 

169 

253.5 

338 

507 

13 

14 

280 

420 

462 

560 

700 

840 

924 

49 

98 

147 

196 

294 

392 

588 

14 

15 

300 

450 

495 

600 

750 

900 

990 

56.25 

112.5 

168.75 

225 

337.5 

450 

675 

15 

16 

320 

480 

528 

640 

800 

960 

1056 

64 

128 

192 

256 

384 

512 

768 

16 

17 

340 

510 

561 

680!  850 

1020 

1122 

72.25 

144.5 

216.75 

289 

433.5 

578 

867 

17 

18 

360 

540 

594 

720 

900 

1080 

1188 

81 

162 

243 

324 

486 

648 

972 

18 

19 

380 

570 

627 

760 

950 

1140 

1254 

90.25 

180.5 

270.75 

361 

541.5 

722 

1083 

19 

20 

400 

600 

660 

800 

1000 

1200 

1320 

100 

200 

300 

400 

600 

800 

1200 

20 

21 

420 

630 

693 

840 

1050 

1260 

1386 

110.25 

220.5 

330.75 

441 

661.5 

882 

1323 

21 

22 

440 

660 

726 

880 

1100 

1320 

1452 

121 

242 

363 

484 

726 

968 

1452 

22 

23 

460 

690 

759 

920 

1150 

1380 

1518 

132.25 

264.5 

396.75 

529 

793.5 

1058 

1587 

2S 

24 

480 

720 

792 

960 

1200 

1440 

1584 

144 

288 

432 

576 

864 

1152 

1728 

24 

25 

500 

750 

825 

1000 

1250 

1500 

1650 

156.25 

312.5 

468.75 

625 

937.5 

1250 

1875 

25 

26 

520 

780 

858 

1040 

1300 

1560 

1716 

369 

338 

507 

676 

1014 

1352 

2028 

2& 

27 

540 

810 

891 

1080 

1350 

1620 

1782 

182.25 

364.5 

546.75 

729 

1093.5 

1458 

2187 

27 

28 

560 

840 

924 

1120 

1400 

1680 

1848 

196 

392 

588 

784 

1176 

1568 

2352 

28 

29 

580 

870 

957 

1160 

1450 

1740 

1914 

210.25 

420.5 

630.75 

841 

1261.5 

1682 

2523 

29- 

30 

600 

900 

990 

1200 

1500 

1800 

1980 

225 

450 

675 

900 

1350 

1800 

2700 

30 

31 

620 

930 

1023 

1240 

1550 

1860 

2046 

240.25 

480.5 

720.75 

961 

1441.5 

1922 

2883 

31 

32 

640 

960 

1056 

12801  1600 

1920 

2112 

256 

512 

768 

1024 

1536 

2048 

3072 

32 

33 

660 

990 

1089 

1320 

1650 

1980 

2178 

272  25 

544.5 

816.75 

1089 

1633.5 

2178 

3267 

33 

34 

680 

1020 

I1  22 

1360 

1700 

2040 

2244 

289'" 

578 

867 

1156 

1734 

2312 

3468 

34 

35 

700 

1050 

1155 

1400 

1750 

2100 

2310 

306.25 

612.5 

918.75 

1225 

1837.5 

2450 

3C75 

35- 

36 

720 

1080 

1188 

1440 

1800 

2160 

2376 

324 

648 

972 

1296 

1944 

2592 

3888 

36- 

37 

740 

1110 

1221 

1480 

1850 

2220 

2442 

342.25 

684.5 

1026.75 

1369 

2053.5 

2738 

4107 

37 

38 

760 

1140 

1254 

1520 

1900 

2280 

2508 

361 

722 

1083 

1444 

2166 

2888 

4332 

38 

39 

780 

1170 

1287 

1560 

1950 

2340 

2574 

380.25 

•760.5 

1140.75 

1521 

2281.5 

3042 

4563 

39» 

40 

800 

1200 

1320 

1600 

20001  2400 

2649 

400 

800 

1200 

1600 

2400 

3200 

4800 

40- 

41 

820 

1230 

1353 

1640 

2050  2460 

2706 

420.25 

840.5 

1260.75 

1681 

2521.5 

3362 

5043 

11 

42 

840 

1260 

1386 

1680 

2100  2520 

2772 

441 

882 

1323 

1764 

2646 

3528 

5292 

42: 

43 

860 

1290 

1419 

1720 

2150  2580 

2838 

462.25 

924.5 

1386.75 

1849 

2773.5 

3698 

5547 

4* 

44 

880 

1320 

1452 

1760 

2200 

2640 

2904 

484 

968 

1452 

1936 

2904 

3872 

5808 

44 

45 

900 

1350 

1485 

1800 

2250 

2700 

2970 

506.25 

1012.5 

1518.75 

2025 

3037.5 

4050 

6075 

45 

46 

920 

1380 

1518 

1840 

2300 

2760 

3036 

529 

1058 

1587 

2116 

3174 

4232 

6348 

4& 

47 

940 

1410  1551 

1880 

2350  2820 

3102 

552.25 

1104.5 

1656.75 

2209 

3313.5 

4418 

6627 

47 

48 

960 

1440  1584 

1920 

2400  2880 

3168 

576 

1152 

1728 

2304 

3456 

4608 

6912 

48 

49 

980 

1470  1617 

1960 

2450 

2940 

3234 

600.25 

1200.5 

1800.75 

2401 

3601.5 

4802 

7203 

4» 

50 

1000 

1500  1650 

2000 

2500 

3000 

3300 

625 

1250 

1875 

2500 

3750 

5000 

7500 

50 

454  HIGHWAY   CONSTRUCTION. 


The  cubical  contents  between  sections  5  and  6  and  between 
sections  7  and  8  maybe  ascertained  by  the  prismoidal  formula;  the 
contents  between  the  zero  point  and  the  continuous  cross-sections 
by  the  following  formula  : 


r./CF.S  .  DE\ 
Cubic  contents  in  feet  =  I  .  OFi  —  r  ---  h  ~o~j- 

680.  Zero  Point.  —  The  zero  point  should  be  found  on  the 
ground.  If  this  has  not  been  done,  it  may  be  ascertained  as  follows  : 
Take  the  cut  and  the  fill  at  the  stations  between  which  it  lies  ;  then, 
the  sum  of  the  cut  and  the  fill  :  the  cut  :  :  the  distance  from  the 
cut  to  the  fill  :  the  distance  from  the  cut  to  the  zero  point. 

681.  Earth-work  Table.  —  Table  LXX  contains  the  contents  in 
cubic  feet  for  each  foot  in  length  of  the  central  portion  and  side 
slopes  of  embankments  or  cuttings.  To  use  table,  note  the  con- 
tents for  the  central  portion  due  to  the  required  base  and  depth, 
add  contents  given  for  the  required  slope  and  depth,  and  multiply 
by  the  length;  the  product  divided  by  27  gives  cubic  yards. 


CHAPTER  XIV. 
DRAINAGE-CULVERTS. 

682.  Drainage. — The  drainage  of  roadways  is  of  two  kinds,  viz., 
surface  and  subsurface.     The  first  provides  for  the  speedy  removal 
of  all  water  falling  on  the  surface  of  the  pavement;  the  second 
provides  for  the  removal  of  the  underground  water  found  in  the 
body  of  the  road,  a  thorough  removal  of  which  is  of  the  utmost 
importance  and  essential  to  the  life  of  the  road-covering.     A  road- 
covering  placed  on  a  wet  undrained  bottom  will  be  destroyed  by 
both  water  and  frost,  and  will  always  be  troublesome  and  expen- 
sive to  maintain;  perfect  subsoil  drainage  is  a  necessity  and  will 
be  found  economical  in  the  end  even  if  it  requires  considerable 
expense  to  secure  it. 

683.  The  methods  employed  for  securing  the  subsoil  drainage 
must  be  varied  according  to  the  character  of  the  natural  soil,  each 
kind  of  soil  requiring  different  treatment. 

684.  The  natural  soils    may  be   divided  into  the  following 
classes:   silicious,  argillaceous,  and  calcareous;  rock,  swamps,  and 
morasses. 

685.  The  silicious  and  calcareous  soils,  the  sandy  loams  and 
rock  present  no  great  difficulty  in  securing  a  dry  and  solid  founda- 
tion.    Ordinarily  they  are  not  retentive  of  water  and   therefore 
require  no  underdrains;  ditches  on  each  side  of  the  road  will  gener- 
ally be  found  sufficient. 

686.  The  argillaceous  soils  and  softer  marls  require  more  care; 
they  retain  water   and   are   difficult   to   compact,  except   at   the 
surface;  and  they  are  very  unstable  under  the  action  of  water  and 
frost. 

The  drainage  of  these  soils  may  be  effected  by  transverse  drains 
and  deep  side  ditches  of  ample  width.  The  transverse  drains  are 
placed  across  the  road,  not  at  right  angles  but  in  the  form  of  an  in- 

455 


456  HIGHWAY    CONSTRUCTION. 

verted  V  (y\),  with  the  point  directed  up-hill;  the  depth  at  the  angle 
point  should  not  be  less  than  18  inches  helow  the  subgrade  surface, 
and  each  branch  should  descend  from  the  apex  to  the  side  ditches 
with  a  fall  of  not  less  than  1  inch  in  5  feet.  The  distance  apart  of 
these  drains  will  depend  upon  the  wetness  of  the  soil;  in  the  case 
of  very  wet  soil  they  should  be  at  intervals  of  15  feet,  which  may 
be  increased  to  25  feet  as  the  ground  becomes  drier  and  firmer. 

687.  The  transverse  drains  are  best  formed  of  unglazed  circular 
tile  of  a  diameter  not  less  than  3  inches,  jointed  with  loose  collars. 
The  tiles  are  made  from  terra-cotta  or  burnt  clay,  are  porous, 
and  far  superior  to  all  other  kinds  of  drains.  They  carry  off  the 
water  with  greater  ease,  rarely  if  ever  get  choked  up,  and  only 
require  a  slight  inclination  to  keep  the  water  moving  through 
them. 

The  tiles  are  made  in  a  variety  of  forms,  as  horseshoe  sole, 
double  sole,  and  round,  the  name  being  derived  from  the  shape  of 
their  cross-sections.  Eound  tile  is  superior  to  all  other  forms. 
The  inside  diameter  of  these  tiles  varies  from  1£  to  6  inches,  but 
they  are  manufactured  as  large  as  24  inches.  Pieces  of  the  larger 
pipe  serve  as  collars  for  the  smaller  sizes.  They  are  made  in 
lengths  of  12,  14,  and  24  inches,  and  in  thickness  of  shell  from  J 
of  an  inch  to  1  inch. 

The  collar  which  encircles  the  joint  of  the  small  tile  allows  a 
large  opening,  and  at  the  same  time  prevents  sand  and  silt  from 
entering  the  drain.  Perishable  material  should  not  be  used  for 
jointing.  When  laid  in  the  ditch  they  should  be  held  in  place  by 
small  stones.  Connections  should  be  made  by  proper  Y-branches. 

The  outlets  may  be  formed  by  building  a  dwarf  wall  of  brick 
or  stone,  whichever  is  the  cheapest  or  most  convenient  in  the 
locality.  The  outlet  should  be  covered  with  an  iron  grating  to- 
prevent  vermin  entering  the  drain-pipes,  building  nests  and  thus 
choking  up  the  water-way.  (See  Fig.  82.) 

Silt-basins  should  be  constructed  at  all  junctions  and  wherever 
else  they  may  be  considered  necessary;  they  may  be  made  from 
a  single  6-inch  pipe  (Fig.  83),  or  constructed  of  brick  masonry  as 
shown  in  Fig.  84. 

The  trenches  for  the  tiles  should  be  excavated  at  least  3  feet 
wide  on  top  and  12  inches  on  the  bottom.  After  the  tiles  are  laid 
the  trenches  must  be  filled  to  subgrade  level  with  round  field  or 


DRAINAGE — CULVERTS.  457 

cobble  stones;  stones  with  angular  edges  are  unsuitable  for  this 
purpose.  Fine  gravel,  sand,  or  soil  should  not  be  placed  over  the 
drains.  Bricks  and  flat  stones  may  be  substituted  for  the  tiles,  and 
the  trenches  filled  as  above  stated. 

Figs.  78  to  81  show  different  forms  of  underdrains. 

688.  Cost  of  Drains  per  Foot.— The  cost  (including  labor  and 
materials)  of  different  drains  may  be  taken  as  follows : 

2-inch  round  tile $0.19  to  $0.28  per  foot 

3-   "         "       "  0.22  "     0.35   "      " 

4-"        "       "  0.25"     0.40"      " 

Triangular  brick 0.22  "    0.35   "      " 

Brick,  4  inches  by  4  inches 0.40"    0.95"       " 

Stone 0.35"    0.50"      " 

Drainage  with  tiles  will  cost  less  than  with  any  other  material 
and  will  be  more  satisfactory  in  the  end. 

689.  As  tile-drains  are  more  liable  to  injury  from  frost   than 
those  of  either  brick  or  stone,  their  ends  at  the  side  ditches  should 
not  in  very  cold  climates  be  exposed  directly  to  the  weather,  but 
may  terminate  in  blind  drains,  or  a  few  lengths  of  vitrified  clay- 
pipe  reaching  under  the  road  a  distance  of  about  3  to  4  feet  from 
the  inner  slope  of  the  ditch. 

690.  Another  method  of  draining  the  road-bed  offering  security 
from  frost  is  by  one  or  more  rows  of  longitudinal  drains.     These 
drains  are  placed  at  equal  distances  from  the  side  ditches  and  from 
each  other,  and  discharge  into  cross-drains  placed  from  250  to  300 
feet  apart,  more  or  less,  depending  on  the  contour  of  the  ground. 
The  cross-drains  into  which  they  discharge  should  be  of  ample 
dimensions.     On  these  longitudinal  lines  of  tiles  the  introduction 
of  catch-basins  at  intervals  of  50  feet  will  facilitate  the  removal  of 
the  water.     These  catch  basins  may  be  excavated  3  or  more  feet 
square  and  as  deep  as  the  tiles  are  laid.     After  the  tiles  are  laid 
the  pit  is  filled  with  gravel  and  small  stones. 

691.  Fall  of  Drains. — It  is  a  mistake  to  give  too  much  fall  tt> 
small  drains,  the  only  effect  of  which  is  to  produce  such  a  current 
through  them  as  will  wash  away  or  undermine  the  ground  around 
them,  and  ultimately  cause  their  own  destruction.     When  a  drain 
is  once  closed  by  any  obstruction  no  amount  of  fall  which  could  be 
given  it  will  again  clear  the  passage.     A  drain  with  a  considerable 
current  through  it  is  much  more  likely  to  be  stopped  from  foreign 


458 


HIGHWAY   CONSTRUCTION. 


TYPES  OF  DRAINS. 


FIG,  78,— BLIND  DRAIN, 


FIG.  79, -POLE  DRAIN. 


FIG,  80.— STONE  DRAIN, 


FIG.  81  .-TILE  DRAIN, 


FIG.  83.— SILT-BASIN.  FIG.  82.— OUTLET.    FIG.  84.— SILT-BASIN, 


DRAINAGE — CULVERTS.  459 

matter  carried  into  it,  which  a  less  rapid  stream  could  not  have 
transported. 

A  fall  of  1  inch  in  5  feet  will  generally  be  sufficient,  and  1  inch 
in  30  inches  should  never  be  exceeded. 

692.  Side  Ditches  are  provided  to  carry  away  the  subsoil-water 
from  the  base  of  the  road,  and  the  rain-water  which  falls  upon  its 
surface;  to  do  this  speedily  they  must  have  capacity  and  inclina- 
tion proportionate  to  the  amount  of  water  reaching  them.     The 
width  of  the  bed  should  not  be  less  than  18  inches;  the  depth  will 
vary  with  circumstances,  but  should  be  such  that  the  water-surface 
shall  not  reach  the  subgrade,  but  remain  at  least  12  inches  below 
the  crown  of  the  road.     The  sides  should  slope  at  least  1^  to  1. 

The  longitudinal  inclination  of  the  ditch  follows  the  configura-  , 
tion  of  the  general  topography,  that  is,  the  lines  of  natural  drain-  \ 
age.     When  the  latter  has  to  be  aided  artificially,  grades  from  1  in 
500  to  1  in  800  will  usually  answer. 

In  absorbing  soil  less  fall  is  sufficient,  and  in  certain  cases  level 
ditches  are  permissible.  The  slopes  of  the  ditches  must  be  pro- 
tected where  the  grade  is  considerable.  This  can  be  accomplished 
by  sod  revetments,  riprapping,  or  paving. 

These  ditches  may  be  placed  either  on  the  road  or  land  side  of 
the  fence.  In  localities  where  open  ditches  are  undesirable  they 
may  be  constructed  as  shown  in  Figs.  87  to  89,  and  may  be  formed 
of  stone  or  tile  pipe,  according  to  the  availability  of  either  material. 
If  for  any  reason  two  cannot  be  built,  build  one;  it  is  better  than 
none. 

Springs  found  in  the  road-bed  should  be  tapped  and  led  into 
the  side  ditches. 

693.  Drainage  of  the  Surface. — The  drainage  of  the  roadway 
surface  depends  upon  the  preservation  of  the  cross-section,  with 
regular  and  uninterrupted  fall  to  the  sides,  without  hollows  or  ruts 
in  which  water  can  lie,  and  also  upon  the  longitudinal  fall  of  the 
road.     If  this  is  not  sufficient  the  road  becomes  flooded  during 
heavy  rain-storms  and  melting  snow,  and  is  considerably  damaged. 

The  removal  of  the  surface-water  from  country  roads  may  be 
effected  by  the  side  ditches,  into  which,  when  there  are  no  sidewalks, 
the  water  flows  directly.  When  there  are  sidewalks,  gutters  are 
formed  between  the  roadway  and  footpath,  as  shown  in  Figs.  85  to 
90,  and  the  water  is  conducted  from  these  gutters  into  the  side 
ditches  by  tile-pipes  laid  under  the  walk  at  intervals  of  about  50 


4GO  *    HIGHWAY   CONSTRUCTION". 

feet.  The  entrance  to  these  pipes  should  be  protected  against 
washing  by  a  rough  stone  paving.  In  the  case  of  covered  ditches 
under  the  footpath,  the  water  must  be  led  into  them  by  first  passing- 
through  a  catch-basin.  These  are  small  masonry  vaults  covered 
with  iron  gratings  to  prevent  the  ingress  of  stones,  leaves,  etc. 
Connection  from  the  catch-basin  to  the  ditch  is  made  by  a  tile-pipe 
about  6  inches  in  diameter.  The  mouth  of  this  pipe  is  placed  a 
few  feet  above  the  bottom  of  the  catch-basin,  and  the  space  below  it 
acts  as  a  depository  for  the  silt  carried  by  the  water,  and  is  cleaned 
out  periodically.  The  catch-basins  may  "be  placed  from  200  to  300 
feet  apart.  They  should  be  made  of  dimensions  sufficient  to  con- 
vey the  amount  of  water  which  is  liable  to  flow  into  them  during 
heavy  and  continuous  rain. 

694.  If  on  inclines  the  velocity  of  the  water  is  greater  than  the 
nature  of  the  soil  will  withstand,  the  gutters   should  be  roughly 
paved.     In  all  cases  the  slope  adjoining  the  foot-path  should  be 
covered  with  sod. 

A  velocity  of  30  feet  a  minute  will  not  distuib  clay  with  sani 
and  stone.  40  feet  per  minute  will  move  coarse  sand.  60  feet  a 
minute  will  move  gravel.  120  feet  a  minute  will  move  round  pebbles 
1  inch  in  diameter,  and  180  feet  a  minute  will  move  angular  stones 
If  inches  in  diameter. 

The  scour  in  the  gutters  on  inclines  may  be  prevented  by  small 
weirs  of  stones  or  fascines  constructed  by  the  roadmen  at  a  nominal 
cost.  At  junctions  and  cross-roads  the  gutters  and  side  ditches 
require  careful  arrangement  so  that  the  water  from  one  road  may 
not  be  thrown  upon  another;  cross-drains  and  culverts  will  be  re- 
quired at  such  places. 

695.  Water-breaks  to  turn  the  surface-drainage  into  the  side 
ditches  should  not  be  constructed  on  improved  roads.     They  in- 
crease the  grade  and  are  an  impediment  to  convenient  and  easy 
travel.     Where  it  is  necessary  that  water  should  cross  the  road 
a  culvert  should  be  built. 

696.  On  side  hill  or  mountain  roads  catch-water  ditches  should 
be  cut  on  the  mountain  side  above  the  road,  to  cut  off  and  convey 
the  drainage  of  the  ground  above  them  to  the  neighboring  ravines. 
The  size  of  these  ditches  will  be  determined  by  the  amount  of 
rainfall,  extent  of  drainage  from  the  mountain  which  they  inter- 
cept, and  by  the  distances  of  the  ravine  water-courses  on  each  side. 

The  inner  road-gutter  should  be  of  ample  dimensions  to  carry 


DRAINAGE— CULVERTS. 


461 


CROSS-SECTIONS  OF  ROADS,  SHOWING  METHODS  OF  DRAINING 
AND  DIVISION  INTO  WHEELWAY,  WALKS,  ETC. 


Hg.85, 


Fig.87: 


462  HIGHWAY    CONSTRUCTION. 

off  the  water  reaching  it;  when  in  soil  it  should  be  roughly  paved 
with  stone.  Where  paving  is  not  absolutely  necessary,  but  it  is 
desirable  to  arrest  the  scouring  action  of  running  water  during 
heavy  rains,  stone  weirs  may  be  erected  across  the  gutter  at  conveni- 
ent intervals.  The  outer  gutter  need  not  be  more  than  12  inches 
wide  and  9  inches  deep.  The  gutter  is  formed  by  a  depression  in 
the  surface  of  the  road  close  to  the  parapet  or  revetted  earthen 
protection-mound.  The  drainage  which  falls  into  this  gutter  is  to 
be  led  off  through  the  parapet,  or  other  road-side  protection  at  fre- 
quent intervalso  The  guard-stones  on  the  outer  side  of  the  road 
are  to  be  placed  in  and  across  this  gutter,  just  below  the  drainage- 
holes,  so  as  to  turn  the  current  of  the  drainage  into  these  holes  or 
channels.  On  straight  reaches  with  parapet  protection,  drainage- 
holes  with  guard-stones  should  be  placed  every  20  feet  apart. 
Where  earthen  mounds  are  used,  and  it  may  not  be  convenient 
to  have  the  drainage-holes  or  channels  every  20  feet,  the  guard - 
stones  are  to  be  placed  in  advance  of  the  gutter  to  allow  the  drain- 
age to  pass  behind  them.  This  drainage  is  either  to  be  run  off  at 
the  cross-drainage  of  the  road,  or  to  be  turned  off  as  before  by  a. 
guard-stone  set  across  the  gutter. 

At  re-entering  turns,  where  the  outer  side  of  the  road  requires- 
particular  protection,  guard-stones  should  be  placed  every  4  feet. 
As  all  re-entering  turns  should  be  protected  by  parapets,  the 
drainage-holes  through  them  may  be  formed  as  close  together  as- 
desired. 

697.  Culverts.— Culverts   are   necessary  for  carrying  under  a- 
road  the  streams  it  crosses,  and  also  for  conveying  the  surface1- 
water  collected  in  the  side  ditches  from  the  upper  side  to  that  side 
on  which  the  natural  water-courses  lie. 

698.  Especial  care  is  required  to  provide  an  ample  way  for  the 
water  to  be  passed.     If  the  culvert  is  too  small,  it  is  liable  to  cause= 
a  washout,  entailing  interruption  of  traffic  and  cost  of  repairs,  and 
possibly  may  cause  accidents  that  will  require  the  payment  of  large 
sums  for  damages.     On  the  other  hand,  if  the  culvert  is  made  un- 
necessarily large,  the  cost  of  construction  is  needlessly  increased. 
Any  one  can  make  a  culvert  large  enough;  but  it  is  the  province  of 
the  engineer  to  design  one  of  sufficient  but  not  extravagant  size. 

699.  The   area  of  water-way   required   depends  (1)  upon   the 
rate  of  rainfall;  (2)  the  kind  and  condition  of  the  soil;  (3)  the 
character  and  inclination  of  the  surface;  (4)  the  condition  and  in- 
clination of  the  bed  of  the  stream;  (5)  the  shape  of  the  area  to  be 


DRAINAGE— CULVERTS. 


463 


drained,  and  the  position  of  the  branches  of  the  stream  ;  (6)  the 
form  of  the  mouth  and  the  inclination  of  the  bed  of  the  culvert ; 


t 

LJ 

CC. 

fe 

1 

DC 

CO 
ID 

co 
oi 


CROSS-SECTIONS  OF  ROADS,  ILLUSTRATING  DRAINAGE,  ETC. 

and  (7)  whether  it  is  permissible  to  back  the  water  up  above  the 
culvert,  thereby  causing  it  to  discharge  under  a  head. 

(1)  It   is   the    maximum   rate   of  rainfall  during  the  severest 
storms  which  is  required  in  this  connection.     This  certainly  varies 


464  HIGHWAY   CONSTRUCTION. 

greatly  in  different  sections,  but  there  are  almost  no  data  to  show 
what  it  is  for  any  particular  locality,,  since  records  generally  give 
the  amount  per  day  and  rarely  per  hour,  while  the  duration  of  the 
storm  is  seldom  recorded.  Further,  probably  the  longer  the  series 
of  observations  the  larger  will  be  the  maximum  rate  recorded, 
since  the  heavier  the  storm  the  less  frequent  its  occurrence;  and 
hence  a  record  for  a  short  period,  however  complete,  is  of  but  little 
value  in  this  connection.  Further,  the  severest  rainfalls  are  of 
comparatively  limited  extent,  and  hence  the  smaller  the  area  the 
larger  the  possible  maximum  precipitation.  Finally,  the  effect  of 
the  rainfall  melting  snow  would  have  to  be  considered  in  deter- 
mining the  maximum  amount  of  water  for  a  given  area. 

The  maximum  rainfall  as  shown  by  statistics  is  about  one  inch 
per  hour  (except  during  heavy  storms),  equal  to  3630  cubic  feet 
per  acre.  Owing  to  various  causes,  not  more  than  50  to  75  per 
cent  of  this  amount  will  reach  the  culvert  within  the  same  hour. 

Inches  of  rainfall  X  3630  =  cubic  feet  per  acre. 

Inches  of  rainfall  X  2,323,200  =  cubic  feet  per  square  mile. 

(2)  The  amount  of  water  to  be  drained  off  will  depend  upon 
the  permeability  of  the  surface  of  the  ground,  which  will  vary 
greatly  with  the  kind  of  soil,  the  degree  of  saturation,  the  condi- 
tion of  the  cultivation,  the  amount  of  vegetation,  etc. 

(3)  The  rapidity  with  which  the  water  will  reach  the  water- 
course depends  upon  whether  the  surface  is  rough  or  smooth,  steep 
or  flat,  barren  or  covered  with  vegetation,  etc. 

(4)  The  rapidity  with  which  the  water  will  reach  the  culvert 
depends  upon  whether  there  is  a  well-defined  and  unobstructed  chan- 
nel, or  whether  the  water  finds  its  way  in  a  broad  thin  sheet.     If 
the  water-course  is  unobstructed  and  has  a  considerable  inclination, 
the  water  may  arrive  at  the  culvert  nearly  as  rapidly  as  it  falls ; 
but  if  the  channel  is  obstructed,  the  water  may  be  much  longer  in 
passing  the  culvert  than  in  falling. 

(5)  The  area  of  the  water-way  depends  upon  the  amount  of  the 
area  to  be  drained;  but  in  many  cases  the  shape  of  this  area  and 
the  position  of  the  branches  of  the  stream  are  of  more  importance 
than  the  amount  of  the  territory.     For  example,  if  the  area  is  long 
and  narrow,  the  water  from  the  lower  portion  may  pass  through 
the   culvert  before  that  from  the  upper  end  arrives;   or,  on  the 
other  hand,   if  the  upper  end  of  the  area  is  steeper  than  the 
lower,  the  water  from  the  former  may  arrive  simultaneously  with 


DRAINAGE  —  CULVEETS.  465 

that  from  the  latter.  Again,  if  the  lower  part  of  the  area  is 
better  supplied  with  branches  than  the  upper  portion,  the  water 
irom  the  former  will  be  carried  past  the  culvert  before  the  arrival 
of  that  from  the  latter;  or,  on  the  other  hand,  if  the  upper  portion 
is  better  supplied  with  branch  water-courses  than  the  lower,  the 
water  from  the  whole  area  may  arrive  at  the  culvert  at  nearly  the 
same  time.  In  large  areas  the  shape  of  the  area  and  the  position 
of  the  water-courses  are  very  important  considerations. 

(6)  The  efficiency  of  a  culvert  may  be  materially  increased  by 
so  arranging  the  upper  end  that  the  water  may  enter  it  without 
being  retarded.     The  discharging  capacity  of  a  culvert  can  al?o  be 
increased  by  increasing  the  inclination  of  its  bed,  provided  the 
channel  below  will  allow  the  water  to  flow  away  freely  after  having 
passed  the  culvert. 

(7)  The  discharging  capacity  of  a  culvert  can  be  g:e&tly  in- 
creased by  allowing  the  water  to  dam  up  above  it.     A  culvert  wiJl 
discharge  twice  as  much  under  a  head  of  four  feet  as  under  a  head 
of  one  foot.     This  can  be  done  safely  only  with  a  well-constructed 
culvert. 

700.  The  determination  of  the  values  of  the  different  factors 
entering  into  the  problem  is  almost  wholly  a  matter  of  judgment. 
An  estimate  for  any  one  of  the  above  factors  is  liable  to  be  in  error 
from  100  to  200  per  cent,  or  even  more,  and  of  course  any  result 
deduced  from  such  data  must   be  very  uncertain.     Fortunately, 
mathematical  exactness  is  not  required  by  the  problem  nor  war- 
ranted by  the  data.     The  question  is  not  one  of  10  or  20  per  cent 
of  increase;  for  if  a  2-foot  pipe  is  insufficient,  a  3-foot  pipe  will 
probably  be  the  next  size,  an  increase  of  225  per  cent;  and  if  a  6- 
foot  arch-culvert  is  too  small,  an  8-foot  will  be  used,  an  increase  of 
180  per  cent.     The  real  question  is  whether  a  2-foot  pipe  or  an 
8-foot  arch-culvert  is  needed. 

701.  Calculating  Area  of  Water-way.  —  Numerous  empirical  for- 
mulas have  been  proposed  for  this  and  similar  problems;  but  at 
best  they  are  all  only  approximate,  since  no  formula  can  give  ac- 
curate results  with  inaccurate  data. 

702.  Mr.  Rudolph  Hering,   O.E.,  gives  the  following  formula 
for  calculating  the  size  of  the  water-way  for  culverts  and  drains: 


Q  = 


46G  HIGHWAY   CONSTKUCTIOX. 

in  which 

Q  =  the  number  of  cubic  feet  per  acre  per  second  reaching  the 

mouth  of  the  culvert  or  drain. 
C  ==  a  coefficient  ranging  from  .31  to  .75,  depending  upon  the 

nature  of  the  surface;   .62  is  recommended  for  general 

use. 
r  =  average  intensity  of  rainfall  in  cubic  feet  per  acre  per 

second. 

S  =  the  general  grade  of  the  area  per  thousand  feet. 
A  —  the  area  drained,  in  acres. 

703.  Valuable  data  on  the  proper  size  of  any  particular  culvert 
may  be  obtained  (1)  by  observing  the  existing  openings  on  the  same 
stream:  (2)  by  measuring,  preferably  at  time  of  high  water,  a  cross- 
section  of  the  stream  at  some  narrow  place;  and  (3)  by  determining 
the  height  of  high  water  as  indicated  by  drift  and  the  evidence  of 
the  inhabitants  of  the  neighborhood.     With  these  data  and  a  care- 
ful consideration  of  the  various  matters  referred  to  in  Art.  674, 
it  is  possible  to  determine  the  proper  area  of  water-way  with  a 
reasonable  degree  of  accuracy. 

704.  On  mountain  roads  or  roads  subjected  to  heavy  rainfall 
culverts  of  ample  dimensions  should  be  provided  wherever  required,: 
and  it  will  be  more  economical  to  construct  them  of  masonry.   In 
localities  where  boulders  and  other  debris  are  likely  to  be.  washed 
down  during  wet  weather,  it  will  be  a  good  precaution  to  construct 
catch-pools  at  the  entrance  of  all  culverts  and  cross-drains  for  the 
reception  of  such  matter.     In  hard  soil  or  rock  these  catch-pools 
will  be  simple  well-like  excavations,  with  their  bottom  two  or  three 
feet  below  the  entrance-sill  or  floor  of  the  culvert  or  drain.     Where 
the  soil  is  soft  they  should  be  lined  with  stone  laid  dry ;  if  very  soft, 
with  masonry.     The  size  of  the  catch-pools  will  depend  upon  the 
widths  of  the  drainage  works.     They  should  be  wide  enough  ta 
prevent  the  drains  from  being  injured  by  falling  rocks  and  stones 
of  a  not  inordinate  size. 

The  use  of  catch-pools  obviates  the  necessity  of  building  cul- 
verts and  drains  at  an  angle  to  the  axis  of  the  road.  Oblique 
structures  are  objectionable,  as  being  longer  than  if  set  at  right 
angles,  and  by  reason  of  the  acute-  and  obtuse-angled  terminations 
to  their  piers,  abutments,  and  coverings. 

705.  Materials  for  Culverts. — Culverts  may  be  of  stone,  brick. 


DRAINAGE— CULVERTS.  467 

vitrified  earthenware,  cement,  or  iron  pipe.  Wood  should  be  ab- 
solutely avoided. 

For  small  streams  and  for  a  limited  surface  of  rainfall  either 
class  of  pipes,  in  sizes  varying  from  12  to  24  inches  in  diameter,  will 
serve  excellently.  They  are  easily  laid,  and  if  properly  bedded, 
with  the  earth  tamped  about  them, are  very  permanent.  Their  upper 
surface  should  be  at  least  18  inches  below  the  road-surface,  and  the 
upper  end  should  be  protected  with  stone  paving  so  arranged  -  that 
the  water  can  in  no  case  work  in  around  the  pipe. 

When  the  flow  of  water  is  estimated  to  be  too  great  for  two 
lines  of  24-inch  pipes,  a  culvert  is  required.  If  stone  abounds,  it 
may  be  built  of  large  roughly  squared  stones  laid  either  dry  or  in 
mortar.  When  the  span  required  is  more  than  5  feet,  arch-culverts 
either  of  stone  or  brick  masonry  may  be  employed.  For  spans 
above  15  feet  the  structure  required  becomes  a  bridge. 

706.  Cement  and  Earthenware  Pipe  Culverts. — Construction. — 
In  laying  the  pipe  the  bottom  of  the  trench  should  be  rounded 
out  to  fit  the  lower  half  of  the  body  of  the  pipe  with  proper  de- 
pressions for  the  sockets.  If  the  ground  is  soft  or  sandy,  the 
earth  should  be  rammed  carefully,  but  solidly  in  and  around  the 
lower  part  of  the  pipe.  The  top  surface  of  the  pipe  should,  as  a 
rule,  never  be  less  than  18  inches  below  the  surface  of  the  roadway, 
but  there  are  many  cases  where  pipes  have  stood  for  several  years 
under  heavy  loads  with  only  8  to  12  inches  of  earth  over  them.  No 
danger  from  frost  need  be  apprehended,  provided  the  culverts  are 
so  constructed  that  the  water  is  carried  away  from  the  level  end. 
Ordinary  soft  drain-tiles  are  not  in  the  least  affected  by  the  expan- 
sion of  frost  in  the  earth  around  them. 

The  freezing  of  water  in  the  pipe,  particularly  if  more  than 
half  full,  is  liable  to  burst  it ;  consequently  the  pipe  should  have  a 
sufficient  fall  to  drain  itself,  and  the  outlet  should  be  so  low  that 
there  is  no  danger  of  back-waters  reaching  the  pipe.  If  properly 
drained,  there  is  no  danger  from  frost. 

Jointing. — In  many  cases,  perhaps  in  most,  the  joints  are  not 
calked.  If  this  is  not  done,  there  is  liability  of  the  waters  being- 
forced  out  at  the  joints  and  washing  away  the  soil  from  around  the 
pipe.  Even  if  the  danger  is  not  very  imminent,  the  joints  of  the 
larger  pipes,  at  least,  should  be  calked  with  hydraulic  cement,  since 
the  cost  is  very  small  compared  with  the  insurance  against  damage 


468 


HIGHWAY    CONSTRUCTION. 


ABUTMENTS  FOR  PIPE   CULVERTS. 


vv™ 


J 


Fig.  93 


Pig  94, 


Fig.95 


Fig.96,. 


DRAINAGE — CULVERTS. 


469 


thereby  secured.  Sometimes  the  joints  are  calked  with  clay. 
Every  culvert  should  be  built  so  that  it  can  discharge  water  under 
a  head  without  damage  to  itself. 

The  end  sections  should  be  protected  with  a  masonry  or  timber 


Fig.  96a.    SINGLE   PIPE  CULVERT. 


18"  =  1 2' I '/a  \ 


Fig.  96b.     DOUBLE   PIPE  CULVERT. 

bulkhead,  although  it  is  often  omitted.  A  parapet  wall  of  rubble 
masonry  or  brick-work  laid  in  cement  is  best  (see  Fig.  93).  The 
foundation  of  the  bulkhead  should  be  deep  enough  not  to  be  dis- 
turbed by  frost.  In  constructing  the  end  wall,  it  is  well  to  increase 
the  fall  near  the  outlet  to  allow  for  a  possible  settlement  of  the  in- 
terior sections.  When  stone^nd  brick  abutments  are  too  expensive^ 
a  fair  substitute  can  be  made  by  setting  posts  in  the  ground  and 
spiking  plank  on,  as  shown  in  Fig.  95.  When  planks  are  used,  iti& 


470 


HIGHWAY    CONSTRUCTION-. 


best  to  set  them  with  considerable  inclination  towards  the  roadbed 
to  prevent  their  being  crowded  outward  by  the  pressure  of  the 


Fig.  96c.    TRIPLE   PIPE  CULVERT. 


BROK 
STONES  OR  BRICK 


Fig.  96d.    SECTION   OF   PIPE  CULVERT. 

embankment.     The  upper  end  of  the  culvert  should  be  so  protected 
that  the  water  will  not  readily  find  its  way    along  the    outside 


DKAINAGE — CULVERTS. 


471 


of  the  pipes,  in  case  the  mouth  of  the  culvert  should  become 
submerged. 

When  the  capacity  of  one  pipe  is  not  sufficient,  two  or  more 
may  be  laid  side  by  side  as  shown  in  Figs.  96a  to  96c.  Although 
two  small  pipes  do  not  have  as  much  discharging  capacity  as  a  sin- 
gle large  one  of  equal  cross-section,  yet  there  is  an  advantage  in 
laying  two  small  ones  side  by  side,  since  the  water  need  not  rise  so 
high  to  utilize  the  full  capacity  of  the  two  pipes  as  would  be  neces- 
sary to  discharge  itself  through  a  single  one  of  larger  size. 

707.  Cost. — Price  of  earthenware  and  cement  pipe  vary  greatly 
with  the  conditions  of  trade,  and  with  competition  and  freight. 
Current  (1892)  prices,  subject  from  40  to  65  per  cent  discount  for 
culvert-pipe  in  car-load  lots,  f.  o.  b.  at  the  factory,  are  about  as 
follows : 

TABLE  LXXI. 
COST  AND  WEIGHT  OF  VITRIFIED  CULVERT-PIPE. 


Inside  Diameter. 
Inches. 

Price  per  foot. 
Cents. 

Area. 
Square  feet. 

Weight  per  foot. 
Pounds. 

Number  of  feet 
in  Car-load  of 
24,000  Ibs. 

12 

85 

.78 

48 

500 

15 

125 

1.23 

67 

358 

18 

170 

1.76 

84 

286 

20 

225 

2.18 

99 

242 

24 

325 

3.14 

140 

172 

TABLE  LXXII. 
COST  AND  WEIGHT  OF  PORTLAND  CEMENT-PIPE. 


Inside  Diameter. 
Inches. 

Price  per  foot. 
Cents. 

Area. 
Square  feet. 

Weight  per  foot. 
Pounds. 

Number  of  feet 
in  Car-load  of 
24,000  Ibs. 

12 

85 

.78 

57 

450 

15 

125 

1.23 

77 

320 

18 

178 

1.76 

110 

230 

20 

225 

2.18 

135 

180 

24 

325 

3.14 

165 

150 

708.  Iron  Pipe-culverts. — During  recent  years  iron  pipe  has  been 
used  for  culverts  on  many  prominent  railroads,  and  may  be  used  on 
roads  in  sections  where  other  materials  are  unavailable. 


472 


HIGHWAY   CONSTRUCTION. 


In  constructing  a  culvert  with  cast-iron  pipe  the  points  requir- 
ing particular  attention  are  (1)  tamping  the  soil  tightly  around  the 
pipe  to  prevent  the  water  from  forming  a  channel  along  the  outside, 
and  (2)  protecting  the  ends  by  suitable  head  walls  and,  when  neces- 
sary laying  riprap  at  the  lower  end.  The  amount  of  masonry  re- 
quired for  the  end  walls  depends  upon  the  relative  width  of  the 
embankment  and  the  number  of  sections  of  pipe  used.  For  ex- 
ample, if  the  embankment  is,  say,  40  feet  wide  at  the  base,  the 
culvert  may  consist  of  three  12-foot  lengths  of  pipe  and  a  light  end 
wall  near  the  toe  of  the  bank;  but  if  the  embankment  is,  say,  32 
feet  wide,  the  culvert  may  consist  of  two  12-foot  lengths  of  pipe 
and  a  comparatively  heavy  end  wall  well  back  from  the  toe  of  the 
bank.  The  smaller  sizes  of  pipe  usually  come  in  12-foot  lengths, 
but  sometimes  a  few  6-foot  lengths  are  included  for  use  in  adjust- 
ing the  length  of  the  culvert  to  the  width  of  the  bank.  The  larger 
sizes  are  generally  6  feet  long. 

709.  Cost. — Prices  of  cast-iron  pipe  vary  greatly  with  com- 
petition and  the  conditions  of  trade.  Table  LXXIII  shows  current 
prices  (1892),  subject  to  commercial  discount: 

TABLE   LXXIII. 
DIMENSIONS,  WEIGHT,  AND  PRICES  OF  IRON  PIPE. 


Inside  Diameter. 

Thickness. 

Weight  per  foot. 

Price  per  foot. 

12  inches 

•fc  inch 

60  pounds 

96  cents 

16 

^ 

86 

140 

20 

1 

118 

188 

24 

^ 

175 

280 

30 

.3 

240 

384 

36 

1 

320 

512 

42 

1 

400 

640 

48 

1 

510 

616 

710.  The  approximate  relative  cost  of  the  different  forms  of 
culvert  per  lineal  foot  for  each   square  foot  of  waterway  is   as 
follows : 

Rubble 40  cents 

Earthenware  or  cement  pipe 30     " 

Iron  pipe 46     " 

711.  Stone  Box-culverts,— The  simplest  form  of  stone  culvert 
is  what  is  known  as  the  box-culvert.     It  consists  of  two  side  walls, 


DRAINAGE — CULVERTS. 


473 


EXAMPLES  OF  BOX-CULVERTS. 


L                                                  > 

F~      } 

MfeMMMttl 

EOQS3MEE 

i           i 

FIG,  97,— END  ELEVATION, 


FIG,  99.— PLAN, 


FIG,  98.— SECTION  AB. 


FIG.  100,-SECTION  CD. 


FIG,  101  .—SECTION  OF  CULVERT  ON  A  HILLSIDE, 


J 


474 


HIGHWAY   CONSTRUCTION. 


which  may  be  built  of  stone  laid  dry  or  in  mortar,  and  a  covering 
of  flags.  Where  large  flat  stones  can  readily  be  procured  it  forms 
a  very  economical  structure.  Under  high  embankments  the  thick- 
ness of  the  covering-stone  must  be  increased.  Figs.  97  to  101  show 
the  form  of  this  class  of  culverts  and  the  dimensions  given  in 
Table  LXXIV  will  serve  as  an  approximate  guide  for  general 
use. 


TABLE  LXXIV. 
DIMENSIONS  FOR  BOX-CULVERTS. 


Area. 

Opening. 

Side  Wall. 

Depth  of  Cover. 

Length  of  Cover. 

4  feet 

2'  X  2' 

2'X  2' 

12  inches 

5  feet 

9    •' 

3X3 

3  X  2J- 

16      " 

6    " 

16    " 

4X4 

4X3 

20      " 

7    " 

25    " 

5X5 

5  X  3i 

22       " 

8    " 

36    " 

6X6 

6X4 

24      " 

9    " 

712.  Arch-culverts. — The  form  of   an  arch  may  be  the  semi- 
circle, the  segment,  or  a  compound  formed  of  a  number  of  circular 
curves  of  different  radii.     Full-centre  arches  or  entire  semicircles 
offer  the  advantages  of  simplicity  of  form,  great  strength,  and  small 
lateral  thrust;  but  if  the  span  is  large  they  require  a  correspond- 
ingly great  rise,  which  is  often  objectionable.     The  flat  or  segmental 
arch  enables  us  to  reduce  the  rise,  but  it  throws  a  great  lateral 
strain  on  the  abutments.     The  compound  curve  gives,  when  prop- 
erly proportioned,  a  strong  arch,  with  a  moderate  lateral  action,  is 
easily  adjustable  to  different  ratios  between  the  span  and  the  rise, 
and  is  unsurpassed  in  its  general  appearance.     In  striking  the  com- 
pound curve,  the  following  conditions   are   to   be  observed:   the 
tangents  at  the  springing  must  be  vertical,  the  tangent  at  the  crown 
horizontal,  and  the  number  of  centres  must  be  uneven. 

713.  The  depth  of  the  arch-stone,  or  thickness  of  voussoir,  de- 
pends upon  the  form  and  size  of  the  arch,  the  character  of  the 
masonry,  and  the  quality  of  the  stone.     The  following  table  gives 
the  depths  for  semicircular  arches,  the  second  column  being  foi 
hammer-dressed  beds,  the  third  for  beds  roughly  dressed  with  the 
chisel,  and  the  fourth  for  brick  masonry. 


DRAINAGE — CULVERTS. 


475 


EXAMPLE  OP  ARCH-CULVERTS. 

V 


FIG,  102.— SECTIONAL  ELEVATION, 

\\ 

:  c 


FIG.  1 04,— SECTION  AB. 


I    .  j 


J L 


FIG.  1 03, -PLAN, 


ft? 


FIG,  105,— SECTION  CD. 


47G 


HIGHWAY   CONSTRUCTION. 


TABLE  LXXV. 


Thickness  of  Arch  in  inches. 


opaii  111  icet. 

First-class  Masonry. 

Second-class  Masonry. 

Brick  Masonry. 

6 

12 

15 

12 

8 

13 

16 

16 

10 

14 

17 

20 

12 

15 

19 

20 

14 

16 

20 

24 

16 

17 

21 

24 

18 

18 

23 

24 

20 

19 

24 

24 

25 

20 

25 

28 

30 

21 

26 

28 

35 

22 

28 

28 

40 

23 

29 

32 

45 

24 

30 

32 

50 

25 

31 

32 

Professor  Rankine  remarks  that  the  precise  determination  of 
the  depth  of  the  keystone  of  an  arch  would  be  an  almost  imprac- 
ticable problem  from  its  complexity,  and  that  the  best  course  in 
practice  is  to  assume  a  depth  for  the  keystone  according  to  an 
empirical  rule  founded  upon  the  dimensions  of  good  existing  ex- 
amples of  bridges.  For  such  a  rule  he  gives  the  following : 

Depth  in  feet  =  |/(.12  radius  at  crown)  for  a  single  arch. 

Depth  in  feet  =  4/(.17  radius  at  crown)  for  an  arch  of  a  series, 
Mr.  Trautwine  gives  the  following  rule' :  For  first-class  cut  stone 
of  hard  material  take  0.36  of  the  square  root  of  the  radius  of  the 
crown;  for  second-class  work,  .40  of  the  square  root;  and  for  brick 
or  rubble  arches,  0.45  of  the  square  root.  The  results  by  the  latter 
are  slightly  in  excess  of  those  by  Professor  Rankine's  formula. 

714.  Thickness  of  Abutments. — Numerous  rules  have  been  given, 
for  obtaining  the  thickness  of  the  abutments  for  arches.  .  The 
most  elaborate  of  these  are  from  their  form  applied  with  difficulty  to 
the  cases  commonly  occurring  in  practice,  and  many  of  the  elements 
entering  into  the  solution  of  the  problem  are  quite  indeterminate,  de- 
pending as  they  do  upon  the  character  of  the  masonry  and  upon 
the  workmanship.  In  place  of  rules,  therefore,  we  present  merely 
an  empirical  table,  embracing  the  results  of  a  considerable  degree 
of  practice. 


DRAINAGE — CULVERTS. 


EXAMPLE  OF  ARCH-CULVERTS. 


FIG.  106.-END  ELEVATION, 

FA 


1 


I 


IB 


FIG.  107.-PLAN. 


-til* 

~<-    v,r 


i>f 


fii//////////////////, 

*  fysf/wr///ty  w//s 


.  1  08.— SECTION  AB. 


478 


HIGHWAY    CONSTRUCTION. 


Table  LXXVI  gives  the  minimum  thickness  of  abutments  for 
arches  of  120  degrees  where  the  depth  of  crown  does  not  exceed  3. 
feet. 

Calculated  from  the  formula 


25 


in  which  D  =  depth  or  thickness  of  crown  in  feet; 

H  =  height  of  abutment  to  springing  in  feet; 
R  =  radius  of  arch  at  crown  in  feet; 
T  =  thickness  of  abutment  in  feet. 


TABLE  LXXVI. 

MINIMUM  THICKNESS  OP  ABUTMENTS  FOR  ARCHES  OF  120  DEGREES 
WHERE  THE  DEPTH  OF  CROWN  DOES  NOT  EXCEED  3  FEET. 


Span  of 
Arch. 

Height  of  Abutment  to  Springing,  in  feet. 

5 

7.5 

10 

20 

30 

8  feet 

3.7 

4.2 

4.3 

4.6       1 

4.7 

9 

3.9 

4.4 

4.6 

4.9 

5.0 

10 

4.2 

4.6 

4.8 

5.1 

5.2 

12 

4.5 

4.7 

5.2 

5.6 

5.7 

14 

4.7 

5.2 

5.5 

6.0 

6.1 

16 

4.9 

5.5 

5.8 

6.4 

6.5 

18 

5.1 

5.8 

6.1 

6.7 

B.9 

20 

5.3 

6.0 

6.4 

7.1 

7.3 

22 

5.5 

6.2 

6.6 

7.3 

7.6 

24 

5.6 

6.4 

6.9 

7.6 

7.9 

30 

6.0 

7.0 

7.5 

8.4 

8.8 

40 

6.5 

7.7 

8.4 

9.6 

10.0 

50 

6.9 

8.2 

9.1 

10.5 

11.1 

60 

7.2 

8.7 

9.7 

11.4 

12.0 

70 

7.4 

9.1 

10.2 

11.8 

12.  £ 

80 

7.6 

9.4 

10.6 

12.8 

13.  ft 

90 

7.8' 

9.7 

11.0 

13.4 

14.3 

100 

7.9 

10.0 

11.4 

14.0 

15.0 

NOTE. — The  thickness  of  abutment  for  a  semicircular  arch  may  be  taken 
from  the  above  table  by  considering  it  as  approximately  equal  to  that  for  an 
arch  of  120  degrees  having  the  same  radius  of  curvature;  therefore  by  divid- 
ing the  span  of  the  semicircular  arch  by  1.155  it  will  give  the  span  of  the  120- 
degree  arch  requiring  the  same  thickness  of  abutment. 


DRAINAGE— CULVERTS. 


479 


TABLE  LXXVII. 
DIMENSIONS,  WEIGHT,  AND  PRICES  OF  DRAIN-TILE. 


Inside 
Diameter. 
Inches. 

Area  in  inches. 

Weight  per 
foot. 

Price  per  1000 
feet.* 

Curves  and 
Reducers. 
Each.* 

No.  Feet 
to 
Carload. 

2 

3.141 

3 

$15.00 

$0.20 

8000 

3 

7.068 

4* 

25.00 

0.20 

6000 

4 

12.566 

«i 

45.00 

0.25 

4000 

5 

19.655 

9 

75.00 

0.30 

3000 

6 

28.274 

12 

100.00 

0.40 

2200 

7 

38.484 

15 

110.00 

0.50 

2000 

8 

50.265 

22 

150.00 

0.70 

1250 

9 

63.617 

26 

200.00 

0.75 

1000 

10 

78.539 

33 

250.00 

1.00 

850 

12 

113.09 

44 

325.00 

1.25 

750 

15 

176.71 

60 

450.00 

1.50 

500 

18 

254.46 

92 

700.00 

2.25 

350 

20 

314.16 

106 

1000.00 

3.00 

250 

21 

345.00 

110 

1250.00 

4.00 

225 

24 

452.39 

150 

1625.00 

5.00 

200 

*  Subject  to  discount. 

TABLE  LXXVIII. 
DISCHARGING  CAPACITY  OF  CIRCULAR  PIPES  IN  CUBIC  FEET  PER  MINUTE. 


Diameter 

Inclination.    Inches  per  100  feet. 

Pipe. 

3 

6 

9 

12 

24 

inches 

cu.  ft. 

cu.  ft. 

cu.  ft. 

cu.  ft. 

cu.  ft. 

2 

1.71 

2.54 

3.07 

3.61 

4.95 

3 

3.07 

4.68 

5.34 

6.16 

8.56 

4 

6.28 

8.82 

10.82 

12.43 

17.51 

8 

35.42 

30.01 

61.49 

70.72 

100.26 

9 

47.46 

67.24 

82.48 

95.05 

161.23 

12 

97.59 

138.10 

170.18 

196.25 

277.54 

15 

171.37 

243.04 

297.32 

329.41 

483.55 

18 

270.32 

383.69 

468.98 

540.77 

749.18 

20 

327.54 

461.23 

558.82 

649.73 

914.43 

24 

555.08 

784.89 

962.83 

1176.87 

1570.05 

CHAPTER  XV. 

BRIDGES,  RETAINING- WALLS,  PROTECTION  WORKS,  TUNNELS, 

FENCING. 

715,  Bridges. — The   construction  of  bridges  is   an   important 
subject,  and  should  not  be  attempted  without  the  professional  ser- 
vices of  a  civil  engineer.     Neglect  of  this  precaution,  and  an  inad- 
equate conception  by  the  people  of  the  risks  to  their  own  and  other 
persons'  lives  produced  by  faulty  bridge  design,  are  causes  to  which 
may  be   attributed   many   of  the   numerous  failures   of   highway 
bridges  annually  recorded. 

As  the  subject  is  so  extensive,  but  a  few  general  remarks  will 
be  made  in  this  volume. 

No  one  bridge  is  adapted  to  every  situation;  each  one  must  be. 
designed  to  sustain  the  amount  and  character  of  the  load  to  which 
it  will  be  subjected. 

716.  All  bridges  should  be  proportioned  to  sustain  the  strains 
produced  by  the  following  loads : 

/  (1)  TJie  dead  load,  which  is  the  weight  of  the  structure  itself, 
and  in  certain  cases  some  extraneous  loading.  The  dead  load  is 
taken  as  uniformly  distributed  over  the  bridge. 

,/"  (2)  The  live  load.  The  live  load  on  a  bridge  is  the  moving  load 
passing  over  it.  In  calculating  the  dimensions  of  the  several  parts 
forming  the  superstructure  of  a  bridge,  the  heaviest  load  which  is 
likely  to  traverse  it  should  be  taken. 

Lii7e  loads  are  of  varied  character;  they  comprise  the  weight  of 
loaded  vehicles  passing  either  singly  or  in  continuous  strings,  por- 
table engineSj  agricultural  machinery,  steam  road-rollers,  and  the 
weight  of  a  crowd  of  people  densely  packed. 

(3)  The  wind-pressure,  including  both  direct  and  indirect  effects. 

(4)  Variations  of  temperature. 

Valuable  information  on  the  subject  of  highway  bridges  is  to  be 

480 


BRIDGES,  RETAINING-WALLS,  TUNNELS,  ETC.  481 

found  in  the  specifications  for  highway  bridges  of  iron  and  steel 
by  J.  A.  Waddell. 

717.  Nothing  improves  the  appearance  and  attractiveness  of  a 
Toad  so  much  as  a  handsome  bridge.     And  it  need  cost  no  more  to 
construct  than  a  homely,  uncouth  structure. 

718.  Materials  for  Bridges. — Bridges  may  be  either  of  stone, 
brick,  wood,  steel,  iron,  or  iron  and  wood.     For  permanence  and 
beauty,  stone  or  stone  and  brick  is  preferable.     Steel  and  iron  make 
handsome  bridges,  but  require  more  attention  than  stone.     Wood 
is  the  least  permanent,  and  cheapest  in  first  cost. 

719.  Timber  Bridges. — In  many  localities  timber  is  the   only 
material  available  for  bridges.     Therefore  a  few  directions  for  their 
-construction  may  be  useful.     The  simplest  form  of  wooden  bridge 
is  that  of  plain  stringers  laid  across  the  stream  and  covered  with 
plank.     The  width  of  the  openings  which  such  beams  span  should 
not  exceed  16  feet.     For  greater  widths,  supports  in  the  form  of 
piles  may  be  introduced,  thus  dividing  the  long  span  into  a  number 
of  shorter  ones;  but  such  supports  are  obstructions  to  the  stream 
and  liable  to  damage  in  time  of  freshets.     It  is,  therefore,  desirable 
to  avoid  their  use.     Other  forms  of  support   must   therefore  be 
devised  for  strengthening  the  beams.     This  may  be  effected  by 
supports  from  below  or  above.     Of  supports  from  below,  the  sim- 
plest are  shorter  timbers   (bolsters  or  corbels)  placed  under  the 
main  ones  to  which  they  are  firmly  bolted,  and  projecting  about 
one  third  of  the  span. 

Still  more  effective  are  oblique  braces  or  struts  supporting  the 
middle  of  the  beam,  and  resting  at  their  lower  ends  in  shoulders 
formed  in  the  abutments.  Similar  braces  may  be  applied  to  the 
bolsters  (Fig.  113);  but  as  the  span  increases,  these  braces  become 
so  oblique  as  to  lose  much  of  their  efficiency.  A  straining-piece 
is  therefore  interposed  between  them.  Openings  up  to  thirty-five 
feet  may  thus  be  spanned. 

For  longer  spans,  the  bolsters,  braces,  and  straining-beams  may 
be  combined  as  in  Fig.  114.  The  principle  of  this  method  may  be 
extended  to  very  wide  openings. 

But  in  many  cases  supports  from  below  may  be  objectionable, 
as  exerting  too  much  thrust  against  the  abutments,  and  being  liable 
to  be  carried  away  by  freshets,  'etc.  The  beams  must  in  such  cases 
be  strengthened  by  supports  from  above. 


482 


HIGHWAY    CONSTRUCTION. 


TYPES  OF  TIMBER  BRIDGES, 


fig  109, 


Fig- 117. 


I 

Fig.llO. 


Fig-.ll! 


Fig-.  119. 


Tig.nz 


Fig.  120. 


r 


Fig.113.  § 


A — K 

•  '  K-SS 


.  12,1. 


{      Fig*  116. 
HEAVY  LINES  WOOD.      LIGHT  LINES  IRON, 


BRIDGES,  RETAINTNG-WALLS,  TUNNELS,  ETC.  483 

The  simplest  form  of  such  is  shown  in  Fig.  115,  in  which  the 
horizontal  beam  is  supported  by  an  upright  "  king-post"  to  which 
it  is  attached  by  an  iron  strap,  or  by  the  upright  "  king-post"  being 
formed  of  two  pieces  bolted  together,  and  enclosing  the  beam  be- 
tween them.  The  king-post  itself  is  supported  by  the  oblique  braces, 
or  struts,  which  rest  against  notches  in  the  horizontal  beam. 

Since  the  king-post  acts  as  a  suspending  tie,  an  iron  rod  may  be 
advantageously  substituted  for  it;  the  struts  may  be  also  stiffened 
by  iron  ties,  binding  them  to  the  main  timbers  as  in  Fig.  116. 

For  longer  spans,  a  straining-beam  may  be  introduced  between 
the  struts  as  in  Fig.  121,  in  which  the  posts  are  represented  as  en- 
closing the  beam. 

The  diagrams  of  simple  bridges,  Figs.  125  to  132,  and  Tables 
LXXIX  and  LXXX  give  the  spans  for  which  they  may  be  em- 
ployed and  the  dimensions  of  the  several  parts. 

Fig.  129  shows  the  iron  washer  used  at  the  end  of  the  beam. 
The  latter  should  be  at  right  angles  to  the  direction  of  the 
rod.  It  is  better  to  have  two  rods  instead  of  one  rod  under  each 
beam.  This  allows  the  rods  to  be  outside  of  the  beam,  as  shown 
in  the  figure,  instead  of  requiring  holes  to  be  bored  through  it, 
thereby  weakening  it.  Fig.  130  shows  the  shoe  used  at  the  foot 
of  the  post  and  which  holds  the  rods  in  place.  Figs.  131  and  132 
show  the  same  method  of  construction  applied  to  bridges  of  greater 
width  and  span. 

Combination  structures  of  wood  and  iron  require  constant 
watchfulness,  to  repair  and  replace  damages  arising  from  decay  or 
defective  material. 

Iron  Bridges. — The  first  cost  of  iron  or  steel  bridges  is  greater 
than  that  of  wood  or  combination  structures;  but  where  economy 
of  the  public  funds  is  desired,  the  first  two  materials  are  to  be  pre- 
ferred, because  the  annual  cost  of  repairs  to  the  wooden  structure 
will  in  a  very  few  years  equal,  if  not  greatly  exceed,  the  additional 
sum  required  for  the  construction  of  the  all-metal  bridge.  More- 
over, the  metal  structure  will  outlive  two  if  not  more  timber  ones. 

Figs.  132a,  1326,  132c  show  types  of  iron  bridges. 

To  ascertain  the  saving  in  favor  of  iron,  see  Chapter  XXIV. 

720.  The  substructures  of  bridges  should  be  of  masonry.  Tim- 
ber should  not  be  used  if  it  can  possibly  be  avoided.  Such  struc- 


484 


HIGHWAY   CONSTRUCTION. 


Fig.  125.    LONGITUDINAL  SECTION, 


VA 


Fig.  126.    TRANSVERSE  SECTION. 


TABLE  LXXIX. 
DIMENSIONS  FOR  FIGS.  125  AND  126. 


Span. 
Feet. 

Girders. 
Inches. 

Floor-beams. 
Inches. 

Floor. 
Inches. 

Railing. 
Inches. 

5 

8  X  10 

6X6 

4 

3X4 

10 

10  X  14 

« 

" 

" 

15 

12  X  18 

'* 

tt 

« 

20 

14  X  22 

« 

M 

Fig.   127.    LONGITUDINAL  SECTION. 


BKIDGES,  KETAINItfG-WALLS,  TUNNELS,  ETC. 


485 


L 


Fig.  128.    TRANSVERSE  SECTION. 


Fig.   129.  Fig.   130. 

DETAIL  OF  WASHER.  DETAIL  OF  SHOE. 


TABLE 
DIMENSIONS  FOR  FIGS.  127  TO  132. 


Span. 

Girders. 

Diameter  of  Rods. 

Post. 

Feet. 

Inches. 

Inches. 

Inches. 

15 

12  X  15 

IT"* 

^X12 

20 

12  X  18 

iff 

3X12 

25 

14  X  18 

2 

3Xl± 

30 

15  X  20 

Sx3* 

4  X  15 

Fig.   131.     LONGITUDINAL  SECTION. 


486 


HIGHWAY   CONSTRUCTION, 


tures  are  unsatisfactory  owing  to  early  decay  caused  by  the  destroy- 
ing action  of  air  and  water. 

For  directions  and  specifications  for  the  construction  of  iron 


Fig.   132.    TRANSVERSE  SECTION. 


and  steel  highway  bridges  the  excellent  specifications  of  Messrs.  G. 
Bouscaren,  Theodore  Cooper,  Edwin  Thacher,  and  J.  A.  Waddell 
may  be  consulted. 

721.  Retaining-walls. — Retaining-walls'  are  structures  of  stone 
laid  dry  or  in  mortar,  and  are  employed  under  various  forms  to  sup- 
port the  sides  of  roads  on  hillsides,  or  places  where  land  for  the 
slopes  is  not  obtainable  (see  Figs.  133  to  136). 

722.  Thickness   of  Walls. — Retaining-walls   require   a   certain 
thickness  to  enable  them  to  resist  being  overthrown  by  the  thrust 
of  the  material  which  they  sustain.     The  amount  of  this  thrust 
depends  upon  the  height  of  the  mass  to  be  supported  and  upon  the 
quality  of  the  material. 

723.  Surcharged  Walls. — A  retaining-wall  is  said  to  be  sur- 
charged when   the  bank  it  retains   slopes  backwards  to  a  higher 
level  than  the  top  of  the  wall ;  the  slope  of  the  bank  may  be  either 
equal  to  or  less,  but  cannot  be  greater,  than  the  angle  of  repose  of 
the  earth  of  the  bank. 

724.  Proportions  of  Retaining-walls. — In  determining  the  pro- 
portions of  retaining-walls  experience,  rather  than  theory,  must  be 
our  guide.     The  proportions  will  depend  upon  the  character  of  the 
material  to  be  retained.     If  the  material  be  stratified  rock  with  in- 


BRIDGES,  RETAINING-WALLS,  TUNNELS,  ETC. 


487 


488 


HIGHWAY   CONSTRUCTION. 


BRIDGES,  KETAINING-WALLS,  TUNNELS,  ETC. 


489 


terposed  beds  of   clay,  earth,   or  sand,  and  if   the  strata   incline 
toward  the  wall,  it  may  require  to  be  of  far  greater  thickness  than 


T 


FIG.  133. 


FIG.  134. 


n\WY\\>>V\\ 
W  ' 


v\\\u\\V 


FIG.  135. 


FIG.  136. 


any  ordinary  retaining-wali ;  because  when  the  thin  seams  of  earth 
become  softened  by  infiltrating  rain,  they  act  as  lubricants,  like 


490  HIGHWAY   CONSTRUCTION. 

soap  or  tallow,  to  facilitate  the  sliding  of  the  rock  strata;  and  thus 
bring  an  enormous  pressure  against  the  wall.  Or  the  rock  may  be 
set  in  motion  by  the  action  of  frost  on  the  clay  seams.  Even 
if  there  be  no  rock,  still  if  the  strata  of  soil  dip  toward  the  wall, 
there  will  always  be  danger  of  a  similar  result ;  and  additional  pre- 
cautions must  be  adopted,  especially  when  the  strata  reach  to  a 
much  greater  height  than  the  wall. 

725.  Form  of  Retaining-walls. — Eetaining-walls  are    built   of 
numerous  forms  of  profile  or  cross-section,  varying  from  the  rect- 
angular to  the   triangular.     A   triangle   is   that   figure   which   is 
theoretically  the  most  economical;  and  the  nearer  that  practical 
conditions  will  allow  of  its  being  conformed  to  the  better. 

All  other  things  being  equal,  the  greater  the  face-batter  the 
greater  will  be  the  stability  of  the  wall;  but  considerations  con- 
nected with  the  functions  of  the  wall  limit  the  full  application  of 
this  condition,  and  walls  are  usually  constructed  with  only  a 
moderate  batter  on  the  face,  the  diminution  towards  the  top  being 
obtained  by  a  back  batter  worked  out  in  a  series  of  offsets.  Walls 
so  designed  contain  no  more  material  and  present  greater  resist- 
ance to  overturning  than  walls  with  vertical  backs. 

726.  Dry  stone  retainiiig-walls  are  best  suited  for  roads  on  ac- 
count  of  their  self-draining  properties  and   their   cheapness.     If 
these  dry  walls  are  properly  filled  in  behind  with  stones  and  chips, 
they  are,  if  well  constructed,  seldom   injured   or  overthrown  by 
pressure  from  behind.     If  the  stone  is  stratified  with  a  flat  cleav- 
age, the  construction  of  retaining  and  parapet  walls  is  much  facili- 
tated.    If  the  stone  has  no  natural  cleavage,  great  care  is  necessary 
to   obtain   a   proper   bond.     If  walls   built  of  such  stone  are  of 
coursed  rubble,  care  is  required  that  the  masons  do  not  sacrifice 
the  strength  of  the  walls  to  the  face  appearance.     The  practice  of 
building  walls  with  square  or  rectangular-faced  stones,  tailing  off 
behind,  laid  in  rows,  one  course  upon  the  other,  the  rear  portions 
of  the  walls  being  of  chips  and  rough  stones,  set  anyhow,  cannot 
be  condemned  too  strongly.     Such  a  construction,  which  is  very 
common,  has  little  transverse  and  no  longitudinal  strength. 

Little  or  no  earth  should  be  used  for  back  filling  if  stone  is 
available.  Where  earth  filling  is  used,  it  should  only  be  thrown  in 
and  left  to  settle  itself;  on  no  account  should  it  be  wetted  and 
rammed. 


BRIDGES,  RETAILING-  WALLS,  TUNNELS,  ETC.  491 

The  foundation  of  retaiuing-walls  should  be  particularly 
secure;  the  majority  of  failures  which  have  occurred  in  such  walls 
have  been  due  to  defective  foundations. 

727.  Failure    of   Retaining-walls.  —  Retaining-walls    generally 
fail  (1)  by  overturning  or  by  sliding,  or  (2)  by  bulging  out  of  the 
body  of  the  masonry.     Sliding  may  be  prevented  by  inclining  tha 
courses  inward.    An  objection  to  this  inclination  of  the  joints  in  dry 
walls  is  that  rain-water,  falling  on  the  battered  face,  is  thereby 
carried  inwards  to  the  earth  backing,  which  thus  becomes  soft  and 
settles.     This  objection  may  be  overcome  by  using  mortar  in  the 
face-joints  to  the  depth  of  a  foot,  or  by  making  the  face  of  the 
wall  nearly  vertical. 

728.  Protection  of  Retaining-walls.  —  The  top  of  the  walls  should 
be  protected  with  a  coping  of  large  heavy  stones  laid  as  headers. 

Where  springs  occur  behind  or  below  the  wall,  they  must  be 
carried  away  by  piping  or  otherwise  got  rid  of. 

The  back  of  the  wall  should  be  left  as  rough  as  possible,  so  as 
to  increase  the  friction  of  the  earth  against  it. 

729.  Weep-holes.  —  In  masonry  walls,  weep-holes  must  be  left 
at  frequent  intervals,  in  very  wet  localities  as  close  as  4  feet,  so  as 
to  permit  the  free  escape  of  any  water  which  may  find  its  way  to 
the  back  of  the  wall.     These  holes  should  be  about  2  inches  wide 
and  should  be  backed  with  some  permeable  material,  such  as  gravel, 
broken  stone,  etc. 

730.  Formula  for  calculating  Thickness  of  Retaining-walls.— 

E  =  weight  of  earth-work  per  cubic  yard. 
W=  weight  of  wall. 
If  =  height  of  wall. 
T  =  thickness  of  wall  at  top. 
T  =  Hx  tabular  number  (Table  LXXXI). 
731.  Surcharged  Walls.—  In  calculating    the  strength  of  sur- 
charged walls  substitute  Y  for  H,  Y  being  the  perpendicular  at 
the  end  of  a  line,  L  =  H  measured  along  the  slope  to  be  retained 
(Fig1.  136). 

Y  =  1.71ff  in  slopes  of  1    :  1  ; 


-l.35.ff  "  "  "2:1; 
=  1.31ff  "  "  "  3  :  1; 
"  "  "  4  :  1. 


492 


HIGHWAY   CONSTRUCTION". 


TABLE  LXXXI. 
COEFFICIENTS  FOR  RETAINING-WALLS. 


E:  W  ::  4  :  5 

E:  W::l  :  1 

Batter  of  Wall 

Clay. 

Sand. 

Clay. 

Sand. 

Iin4 

.083 

.029 

.115 

.054 

1  in  5 

.122 

.065 

.155 

.092 

Iin6 

.149 

.092 

.183 

.118 

1  in  8 

.184 

.125 

.218 

.153 

1  in  12 

.221 

.160 

.256 

.189 

Vertical 

.300 

.239 

.336 

.267 

732.  Eetaining-walls  of  dry  stone  should  not  be  less  than  3  feet 
thick  at  top,  with  a  face  of  1  in  4  and  back  perpendicular,  the 
courses  laid  perpendicular    to    the  face-batter.     Weep-holes  are 
unnecessary  unless  the  walls  are  in  very  wet  situations. 

Eetaining-walls  of  masonry  should  be  at  least  2  feet  thick  at 
top,  back  perpendicular  and  face  battered  at  the  rate  of  1  in  6. 

733.  On    steep    hillside  or    mountain    roads    retaining-walls 
should  be  built — 

(1)  At  all  re-entering  curves. 

(2)  At  all  culverts  and  bridges. 

(3)  On  the  edge  of  precipitous  places,  where  there  is  no  room 
for  a  bank. 

(4)  Where  the  bank  slope  and  the  ground  slope  are  nearly  or 
quite  parallel  to  each  other. 

(5)  Where  a  bank  would  be  of  excessive  length  owing  to  the 
angle  of  the  natural  ground  slope. 

.(6)  Where  a  wall  would  be  cheaper  than  a  bank. 

Retaining-walls  on  the  edge  of  dangerous  precipices,  having  to 
support  great  weight,  should  be  built  of  masonry.  All  others  may 
be  of  dry  stone. 

734.  Protection  of  Roads. — All  roads  should  be  protected,  but 
hillside  and  mountain  roads  which  are  unprotected  can  only  be 
classed  as  dangerous.     Blocks  of  stone  of  not  less  than  2J  to  3 
feet  in  height,  and  set  with  not  more  than  3  feet  between  them, 
afford  a  fair  protection  on  a  mountain  road  not  very  precipitous 


BKIDGES,  KETAINING-WALLS,  TUNNELS,  ETC.  493 

at  its  outer  edge,  and  there  is  an  advantage  attendant  upon  their 
use  that  no  outer  gutter  is  necessary,  for  the  drainage  passes  over 
the  bank  in  every  direction,  and  after  the  first  year  or  two  but 
little  damage  occurs  to  the  banks  from  this  cause. 

735.  The  proper  amount  of  protection  required  for  the  danger- 
ous portions  of  a  mountain  road  is  best  obtained  by  stone  parapets 
and  earthen  mounds.     Parapets  should  not  be  less  than  3  feet  in 
k  eight  and,  if  of  masonry,  1£  feet  in  thickness. 

If  stone  parapets  be  built  dry,  they  should  be  at  least  2  feet  in 
thickness,  and  the  coping  should  be  set  in  mortar;  otherwise  they 
are  too  easily  deranged,  and  cartmen  halting  on  the  road  and 
desiring  to  block  the  wheels  of  their  vehicles  invariably  resort  to 
them  for  a  stone  for  this  purpose.  Next  in  order  of  protection 
afforded  by  the  \ise  of  stone  may  be  mentioned  the  plan  of  placing 
large  blocks  of  rough  stone  and  boulders  on  the  edge  of  the  road 
and  touching  each  other.  If  of  good  size  and  well  set,  considerable 
protection  is  afforded  by  this  method,  which  is  cheap.  Dry  stone 
parapet  walls  should  never  be  employed  if  masonry  walls  can  be 
afforded,  and  should  on  no  account  be  used  on  precipitous  curves. 
Parapets  should  be  employed  to  protect  all  embankments  of  a  road 
which  have  stone-wall  revetments,  and  the  outside  of  all  cuttings 
in  rock.  They  should  also  be  built  on  each  side  of  the  road  at  all 
cross-drainage  works,  and  should  be  adopted  at  all  situations  where 
stone  is  available  from  cuttings.  Where  the  embankments  are  of 
earth,  earthen  mounds  are  to  be  preferred  on  the  score  of  economy. 
These  earthen  mounds  should  not  be  less  than  3  feet  in  height,  and 
they  are  best  formed,  both  for  appearance  and  for  their  own  preser- 
vation, by  being  revetted  with  dry  stone  inside.  Earthen  mounds 
constructed  in  this  manner  afford  the  most  secure  protection  for 
traffic,  as,  if  well  rounded  off  on  the  outer  side,  they  do  not  yield  to 
any  concussion,  however  violent. 

736.  Wooden  railings  should  never  be  employed  to  protect  dan- 
gerous places  on  a  mountain  road.     They  afford  no  real  protection 
to  the  traffic,  but  only  give  a  sense  of  protection  to  passing  vehicl  es 
which  do  not  come  into  collision  with  them,  and  show  to  unexcitei 
animals  that  the  way  is  barred  in  that  direction. 

737.  Besides  the  protection  so  necessary  for  the  safety  of  the 
travelling  public,  the  roads  themselves  require  protection  at  their 


494 


HIGHWAY   CONSTRUCTION. 


edges  from  passing  vehicles.  Cart-wheels,  if  not  prevented  from 
hugging  the  very  edge  of  the  road,  and  from  slipping,  either  from 
design  or  accident,  into  the  gutters,  do  great  damage.  Curb-stones 
get  forced  out  of  their  places,  and  if  one  be  displaced,  others  soon, 
follow,  to  the  destruction  of  the  road  edge  as  well  as  of  the  gutters 
themselves.  These  become  blocked  with  loose  stones,  and  when 
rain  falls  greater  destruction  to  the  road  ensues.  It  is  necessary, 
therefore,  to  protect  the  edges  of  mountain  roads  where  they  are 
likely  to  be  damaged  by  wheel  traffic,  which  occurs  chiefly  on  the? 
inside  of  salient  and  outside  of  re-entering  curves. 

738.  Guard-stones  about  9  inches  square  and  of  sufficient  length 
should  be  placed  every  4  or  5  feet  apart  at  the  curbs,  clear  of  the 


FIG.  137. 


gutter,  on  the  hill  side  of  salient  curves.  The  re-entering  curves 
must  also  be  protected  on  the  inner  curve,  which  is  the  outer  side 
of  the  roadway,  by  means  of  similar  guard-stones,  which,  however,, 
in  this  situation  are  set  up  in  the  gutters  themselves. 

739.  Roads  along  the  seashore,  margin  of  rivers  and  lakes,  may 
be  constructed  according  to  either  of  the  methods  shown  in  Figs. 
137  to  139. 

In  Fig.  137,  two  rows  of  piles,  spaced  about  10  feet  centre  to 
centre,  are  driven,  one  row  along  the  toe  of  the  slope  and  another 
along  the  crest  of  the  slope,  and  capped  with  a  3-inch  plank ;  be- 
tween each  pile  and  fastened  thereto  a  4  X  6  inch  or  heavier  stringer 
is  placed.  On  these  stringers  a  layer  of  matched  tongued  and 
grooved  plank  2  or  3  inches  thick  are  laid  and  spiked. 

In  Fig.  138  a  bulkhead  is  formed  as  follows:  a  row  of  piles, 
spaced  6  feet  centre  to  centre,  is  driven  to  a  solid  bearing  and 
capped  with  a  heavy  stick  of  timber.  To  the  piles  waling-sticks 
are  bolted,  one  immediately  at  the  head,  the  other  at  or  below  the 


BRIDGES,  RETAILING- WALLS,  TUNNELS,  ETC. 


495 


natural  surface  of  the  beach;  on  the  land  side  of  the  waling-sticks 
matched  sheet-piling  is  driven  and  spiked  to  the  upper  waling- 
stick.  Anchor-piles  are  driven  on  the  land  side  at  such  distance 
from  the  main  piles  as  will  form  an  angle  of  from  30  to  45  degrees. 
The  main  piles  may  be  fastened  to  the  anchor-piles  by  wrought- 
iron  tie-rods,  and  bevelled  cast-iron  washers  or  timber  may  be  used 


•7737 


FIG.  138. 


for  the  same  purpose.  A  brace-stick  of  either  round  or  square 
timber  should  be  placed  in  the  angle  formed  between  the  tie-rod 
and  head  of  the  anchor  pile.  The  face  of  the  main  piles  at  high- 
water  mark  should  be  protected  by  a  chafing-stick.  Fender-piles 
may  also  be  used  if  the  water  is  navigable  for  large  boats. 


FIG.  139. 

In  Fig.  139  a  masonry  wall  is  shown,  built  on  a  timber  plat- 
form. To  this  class  of  work  the  same  rules  apply  as  to  retaining- 
walls. 

740,  Tunnels. — For  highways,  generally  no  tunnels  can  be  al- 
lowed. They  are  too  costly,  and  can  only  be  employed  under 


496  HIGHWAY    CONSTRUCTION. 

exceptional  circumstances.  If  a  tunnel  would  shorten  the  road  by 
a  length,  the  cost  of  which  would  equal,  or  nearly  so,  the  extra 
cost  of  the  road  through  the  tunnel,  the  construction  of  the  tunnel 
would  be  justified.  The  saving  in  tractive  energy  to  the  public 
using  the  road  would,  in  most  cases,  be  a  saving  too  indirect  to  be 
imported  into  the  calculation. 

741.  Fencing. — Fences  are  usually  built  by  the  property-own- 
ers, but  occasionally  the  road-builder  is  called  upon  to  include 
fencing  in  his  work;  therefore  the  following  few  remarks  may  be 
useful. 

The  requirements  of  a  highway  fence  are  somewhat  different 
Irom  those  of  ordinary  farm  fences.  They  must  possess  sufficient 
strength  to  withstand  the  rough  usage  to  which  they  are  frequently 
subjected.  In  northern  climates  they  must  be  of  such  construc- 
tion as  will  offer  the  least  obstacle  to  drifting  snow  and  thus  pre- 
vent as  much  as  possjjple  the  blocking  of  the  roadway.  In  all 
situations  they  must  be  durable  and  present  a  pleasing  appearance. 

The  materials  employed  for  fences  are  earth  in  the  form  of 
mounds  either  with  or  without  hedges,  stone  laid  dry  or  in  mortar, 
wood  and  metal  in  a  variety  of  forms. 

The  mound  and  ditch  shown  in  Fig.  140  is  much  used  in 
Europe.  The  material  excavated  from  the  ditch  is  thrown  into 


FIG.   140.    DITCH  AND  MOUND  FENCE. 

the  mound  and  a  quickset  hedge  planted  along  the  top.  After  the 
lapse  of  some  time  this  makes  a  good  fence;  but  it  requires  in  the 
interim  a  considerable  amount  of  attention  and  repair. 

In  the  construction  of  fences  which  depend  for  their  support 
upon  posts  set  in  the  ground  the  same  considerations  should  con- 
trol as  in  the  construction  of  any  other  structure,  viz.,  durability  of 
the  material,  strength,  and  stability. 


BRIDGES,   RETAINING   WALLS,   TUNNELS,   ETC.  497 

The  materials  employed  for  the  posts  or  foundations  of  fences 
are  stone  blocks,  wood  and  metal  posts. 

Stone  Posts. — The  durability  of  stone  depends  upon  its  chemi- 
cal constitution  and  physical  structure.  If  the  chemical  constitu- 
ents are  soluble  in  water  the  stone  will  be  short-lived.  If  the  phys- 
ical structure  is  porous  the  stone  will  absorb  water  and  under  the 
action  of  frost  will  be  speedily  split  and  disintegrated.  The  decay 
of  stone  is  more  rapid  at  the  surface  of  the  earth,  where  it  is 
-exposed  to  the  frequent  alternations  of  wet  and  dry  conditions. 
The  horizontal  exposed  surface  should  be  cut  to  such  form  as  will 
readily  shed  water.  Holes  bored  for  the  reception  of  posts,  etc., 
should  be  filled  with  lead,  sulphur,  etc.;  if  not  they  will  act  as 
receptacles  for  water,  allowing  it  to  penetrate  the  interior  of  the 
.stone  and  thus  hasten  its  destruction. 

Wood  Posts. — In  the  selecting  of  wood  for  posts  the  character 
of  the  soil  should  be  considered,  as  it  exercises  considerable  influ- 
ence upon  the  life  of  the  wood.  Sand  and  sandy  loam  are  the  least 
favorable  to  durability  and  clay  the  most  favorable.  The  average 
life  of  the  woods  most  commonly  used  is  about  as  follows:  white 
cedar  twelve  years;  red  cedar  thirty  years;  white  oak  in  sand  five 
years,  in  clay  fifteen  years;  osage  orange  thirty  years;  chestnut 
and  tamarac  twelve  years.  Bois  d'arc  or  bodark  is  very  durable; 
stockades  built  in  Mexico  and  the  Southern  States  over  a  hundred 
years  ago  are  still  in  a  good  state  of  preservation.  Well-seasoned 
timber  will  last  much  longer  than  that  which  is  used  while  green. 
Posts  obtained  from  trees  which  have  been  subjected  to  forest  fires 
will  absorb  water  and  decay  rapidly.  Impregnating  wood  with 
creosote,  chloride  of  zinc,  etc.,  will  about  double  the  life. 

Metal  posts  are  to  be  had  in  a  variety  of  forms.  At  this  time 
there  are  about  thirty  different  styles  on  the  market.  All  the 
different  shapes  in  which  metal  can  be  wrought  have  been  utilized 
with  varying  degrees  of  success.  The  life  of  a  metal  post  depends 
upon  the  perfectness  with  which  it  is  protected  from  rust.  Several 
-coatings  are  in  use,  such  as  coal-tar,  asphaltum,  graphite,  etc.,  but 
their  lasting  qualities  and  the  amount  of  protection  they  afford  to 
the  metal  in  the  presence  of  the  mineral  salts  in  the  earth  is  a 
subject  of  much  controversy. 

The  dimensions  of  posts  must  be  sufficient  to  afford  the  required 


498  HIGHWAY    CONSTRUCTION. 

strength — for  wood  4  inches  square  or  5  inches  in  diameter  will 
usually  be  sufficient;  the  length  of  the  posts  must  be  ample  to  allow 
of  their  being  placed  sufficiently  deep  in  the  ground  to  prevent 
heaving  by  frost.  The  spacing  of  the  posts  will  depend  upon  the 
style  of  fence  and  ought  not  to  exceed  16 J  feet  centre  to  centre. 

In  localities  subject  to  heavy  snowfalls  the  posts  should  be 
spaced  at  short  distances  so  as  to  afford  strength  to  support  the 
load  of  snow.  In  stapling  wire  fences  in  such  localities  the  staples 
may  be  driven  slanting  upwards,  so  that  they  will  pull  out  under 
the  weight;  then  after  the  snow  is  thawed  the  fence  may  be 
restapled  and  restored  to  its  former  good  condition. 

Steel  wire  for  fencing  is  to  be  had  in  a  great  variety  of  shapes,, 
as  plain,  barbed,  braided,  woven,  twisted,  crimped,  etc.  The  object 
of  these  various  shapes  is  to  prevent  sagging  and  provide  for  the 
expansion  and  contraction  of  the  metal  under  the  variations  of 
temperature.  But  these  shapes  are  not  always  advantageous. 
Short  bends  or  kinks,  spirals,  and  coils  are  objectionable,  as  in  the 
process  of  their  formation  the  fibres  of  the  wire  are  injured  and 
the  structure  in  which  they  are  used  is  weak  and  liable  to  destruc- 
tion under  sudden  shock  or  strain.  With  regard  to  the  quality  of. 
the  wire  used  it  should  be  "medium"  steel;  if  too  soft  it  will 
stretch  under  strain  and  consequently  sag  and  become  unsightly; 
if  too  "hard"  it  will  be  liable  to  break  under  sudden  shock.  The 
size  o>f  wire  used  is  generally  No.  12,  and  it  should  have  a  tensile 
strength  of  at  least  800  pounds. 

The  wire,  in  whatever  form  used,  should  be  protected  from 
oxidation.  This  is  effectually  secured  by  galvanizing,  but  the  wire 
should  not  be  galvanized  before  being  twisted,  barbed,  etc.,  for 
much  of  the  coating  will  be  cracked  and  peeled  off  in  the  process 
of  shaping,  and  hence  the  life  of  the  wire  will  be  lessened. 

742.  Height  of  Fences. — The  height  of  the  fence  will  depend 
upon  the  purpose  for  which  it  is  erected.  If  required  to  act  as  a 
barrier  against  cattle  it  should  not  be  less  than  4  ft.  9  in. ;  if  as  a 
protection  to  travellers  on  the  edge  of  banks,  etc.,  3  ft.  6  in.  will 
be  sufficient;  and  if  for  ornamental  purpose  of  such  height  as  may 
please  the  fancy.  Barbed-wire  fences  are  usually  made  four  feet 
high;  the  number  of  wires  used  varies  from  two  to  five,  which  are 
generally  spaced  as  follows : 


BRIDGES,    RETAINING   WALLS,   TUNNELS,   ETC. 


499 


SPACING   OF  BARBED  WIRES. 


Inches  above  Ground. 

Two 
Wires. 

Three 
Wires. 

Four 
Wires. 

Five 
Wires. 

First     wire    ....           , 

22 

40 

15 
30 
48 

16 
25 
35 

48 

8 
16 
25 
35 

48 

Second    "     

Third      "     

Fourth    "     .  .  .  . 

Fifth       "     

743.  Cost  of  Fencing. — The  cost  of  a  plain  or  barbed  wire  fence 
with  wood  posts  and  four  strands  of  wire  will  be  from  $200  to  $250 
per  mile;  a  four-strand  wire  fence  with  steel  posts  will  cost  about 
$350  per  mile.  The  cost  of  woven  and  other  forms  of  wire  with 
metal  posts  will  vary  from  $350  upwards  per  mile.  Common  board 
fence,  posts  set  8  feet  apart,  costs  from  $350  to  $400  per  mile. 

An  estimate  for  a  mile  of  barbed-wire  fence  would  be  about  as 
follows : 

350  posts,  including  braces,  at  10  cents $35.00 

1700  Ibs.  barbed  wire,  at  6  cents 102.00 

40  Ibs.  staples,  at  6  cents 2.40 

Labor , 36.86 

Freight,  tools,  superintendence 3.07 

Total $179.33 

TABLE 

SHOWING  THE  AMOUNT  OF  No.  12  BARB  WIRE  REQUIRED  TO  FENCE 
VARIOUS  DISTANCES. 


IRod. 

10  Rods. 

80  Rods 
or 
i  Mile. 

160  Rods 
or 
i  Mile. 

320  Rods 
or 
1  Mile. 

One  Wire  

Pounds. 
1JL 

Pounds. 
10£ 

Pounds. 
85 

Pounds. 
170 

Pounds. 
340 

Two  Wires     

2A 

21 

170 

340 

680 

Three    "     

3A 

3H 

255 

510 

1020 

Four      "     

4f 

42 

340 

680 

1360 

Five       "     

5T5. 

52* 

425 

850 

1700 

CHAPTER  XVI. 
CITY  STREETS. 

744.  THE  first  work  requiring  the  skill  of  the  engineer  is  to 
properly  lay  out  town  sites,  especially  with  reference  to  the  future 
requirements  of  a  large  city  where  any  such  possibility  exists.  Few 
if  any  of  our  large  cities  were  so  planned.  The  same  principles  to 
a  limited  extent  are  applicable  to  all  towns  or  cities.  The  topo- 
graphy of  the  site  should  be  carefully  studied  and  the  street  lines 
adapted  to  it ;  they  should  be  laid  out  systematically  with  a  view  to 
convenience  and  comfort,  also  with  reference  to  economy  of  con- 
struction, future  sanitary  improvements,  grades,  and  drainage. 

745.  Arrangement  of  City  Streets. — Generally  straight    lines, 
with  frequent  and  regular  intersecting  streets,  is  the  best  method 
of   laying  out   streets,  especially  for    business   parts    of    a  city. 
"When  there  is  some   centrally  located  structure,  such  as  court- 
house, city  hall,  market,  or  other  prominent  public  building,  it  is 
very  desirable  to  have  several  diagonal  streets  leading  thereto.     In 
the  residence  portions  of  cities,  especially  if  on  hilly  ground,  curves 
may  replace   straight  lines  with  advantage  by  affording  better 
grades  at  less  cost  of  grading,  and  improving  property  by  avoiding 
heavy  embankments  or  cuttings. 

746.  The  rectangular  arrangement  of  streets  as  seen  in  New 
York  and  other  cities  is  being  found  objectionable  and  a  bar  to 
convenient    communication;    it  therefore    becomes  necessary  to 
examine  what  other  systems,  if  any,  may  be  used,  and  determine 
their  relative  merits.     The  following  investigation  of  this  subject 
by  Mr.  Lewis  M.  Haupt,  A.M.C.E.,  Professor  of  Civil  Engineering, 
University  of  Pennsylvania,  is  very  interesting,  as  showing  what 
may  be  done  in  the  way  of  opening  diagonal  streets : 

"  The  systems  may  be  divided  into  two  classes :  1st,  regular,  and 
2d,  irregular.  The  first  class  may  be  subdivided  into  rectangular, 
diagonal,  and  ^circular;  the  second  into  every  possible  kind  of  dis- 

500 


CITY   STREETS.  5QI 


tortion  more  or  less  intricate,  according  to  the  circumstances  at- 
tending the  growth  of  a  city.  The  latter  class  is  discarded  as  being 
unscientific,  expensive,  inconvenient,  and  poorly  adapted  to  the 
requirements  of  a  growing  community. 

"  As  people  move  through  a  city  in  every  conceivable  direction,  it 
will  be  impossible  to  provide  the  shortest  lines  for  all ;  but  the  case 
may  be  met  by  supposing  a  greater  or  less  number  of  centres  or 
points  d'appui,  to  and  from  which  the  currents  of  daily  life  flow 
and  ebb. 

"  With  reference  to  the  subdivision  of  the  first  class,  it  is  evident 
that,  the  straight  line  being  the  shortest  distance  between  two 
points,  the  chord  will  be  shorter  than  its  arc,  and  hence  the  circular 
system  is  defective.  The  rectangular  compels  a  waste  of  distance 
and  time,  and  the  diagonal  by  itself  becomes  the  rectangular,  so 
that  no  single  system  fulfils  all  possible  requirements.  A  combina- 
tion must  therefore  be  resorted  to,  and  that  composed  of  right-line 
elements  is  both  the  simplest  and  most  direct.  A  judicious  ar- 
rangement of  diagonal  streets  with  the  rectangular  system  will 
doubtless  be  found  to  meet  more  fully  than  any  other  the  require- 
ments of  the  case ;  but  it  is  evident  that  if  the  streets  be  too  wide  or 
too  numerous,  the  building  areas  will  be  correspondingly  decreased 
and  a  certain  proportion  of  people  forced  beyond  given  limits,  thus 
increasing  their  distances.  On  the  other  hand,  the  diagonals  will 
in  general  open  new  building  lines  with  more  than  residences 
enough  to  provide  for  all  the  displaced  inhabitants. 

"To  illustrate  the  utility  of  such  a  combination,  suppose  a 
portion  of  a  town  or  city  to  be  laid  out  in  the  form  of  a  square 
whose  side  is  L  feet  long,  and  in  which  the  blocks  are  I  feet  square 
and  the  streets  w  feet  wide. 

"  Let  the  diagonals  of  the  large  square  be  opened  as  thorough- 
fares, and  note  their  effect.  The  blocks  or  small  squares  extend 
from  the  middle  of  one  street  to  that  of  its  parallel,  or  from  the 
building  line  of  one  block  to  that  of  the  next;  hence  the  length  of 
a  side  of  such  a  square  must  be  I  -\-iv  (Fig.  141&). 

"  The  area  of  the  small  square,  including  the  streets,  multiplied 
by  the  number  of  such  squares  will  give  the  area  U  of  that  portion 
of  the  city,  and  the  ratio  of  street  to  property  area  is  the  same  for 
the  small  as  for  the  large  squares ;  but  the  area  of  the  small  squares 
is  (/  -\-  w)*  =  r  +  21  w  -+-  w*,  in  which  F  is  the  property  or  build- 


502 


HIGHWAY   CONSTRUCTION. 


ing  area,  and  2hv  -\-  w*  is  the  street  area;  the  ratio  being  - 
and  the  percentage  of  street  to  property  area, 

21  w  -f  w 


T 


100. 


M 


(A) 
P 


DIM: 


r 


n 


< 


n 


\  \ 
\  v 


n 


D 


ED 


3 


13 

H 

D 


SO 


v\ 

Q'  FIG.  141.     ARRANGEMENT   OF   CITY   STREETS.      N 

For  any  rectangle  with  streets  of  unequal  widths,  the  general 
formula  would  be 

be  +  ad  + 


ac 


-100, 


(A1) 


in  which  a  and  c  are  the  sides  of  the  rectangle  and  b  and  d  the 
widths  of  the  streets.     If  these  quantities  are  equal,  each  to  each 


CITY   STREETS. 


503 


{A1)  becomes  (A).    The  number  (n  )  of  blocks  in  a  given  square 
whose  area  is  Ly  will  be 

U 


(H- 


n  . 


(B) 


"  If  now  two  diagonals,  MN  and  PQ  be  introduced,  it  is  evident 
that  where  they  cross  the  rectangular  streets  no  additional  area  is 
taken  from  the  private  property  of*  the  city,  but  they  will  cut  out  of 


J 


L      JL 


JL 


Area 


1 


w 


r     1 


FIG.  141  a.  FIG.   1416. 

each  of  the  small  squares  which  they  cross  an  area  whose  length  is 


—  -,   breadth    w,   and   whose    area    for    one    block,   T,   is 

A 

—  -}w  (see  Fig.  1416).    For  n  blocks  the  total  building  area 
consumed  from  L'  by   both   diagonals   when   n  is  even  will  be 
2nw  (VW  —  -\  and  the  percentage  of  the  building  area  will  be 

^L(VW  --}x  100,  which  reduces  to 
ri*l*  \  2  / 

-^(2.828?  -  w)100,    '.    •    .    V.    '.     .     (C) 
fit 

tlie  formula  for  diagonals  when  n  is  even.    If  n  be  odd,  G  becomes 
^(2.828/)100  =  282.8  ~  ......     (C1) 


504  HIGHWAY    CONSTRUCTION-. 

"  If  diagonals  be  opened,  benefits  will  accrue  both,  from  the  short- 
ening  of  distance  and  the  additional  frontage  which  will  be  fur- 
nished, while  but  a  small  proportion  of  the  inhabitants  will  be- 
displaced.  The  greatest  economy  in  distance  will  be  in  passing 
from  M  to  0  (Fig.  141),  which  by  the  square  system  is  equal  to  L, 

and  by  the  diagonal  LV%,  the  ratio  being       "*  =  -^  —  =  j~,  the 

numerator  indicating  the  distance  (in  feet)  by  the  diagonals,  th& 
denominator  by  the  squares.  This  gives  a  gain  of  30  per  cent,. 
which  is  the  greatest  amount  possible,  and  from  which  it  diminishes 
to  zero  at  P. 

"  The  total  length  of  frontage  on  the  streets  in  the  square  system 
is  lln*.     The  diagonals  give  an  additional  length  of 
and  the  percentage  of  increase  is  therefore 


In 


"  The  ratio  of  people  displaced  is  the  same  as  that  of  the  area 
consumed  by  diagonals  to  the  entire  area  L*. 

"  To  determine  these  values  for  any  particular  case,  and  so  dis- 
cover whether  or  not  the  diagonals  will  be  beneficial,  let  I  =  500 
feet,  w  =  50  feet,  and  n  =  10. 

"  Formula  (A)  gives  21  as  the  percentage  of  large  or  small 
squares  consumed  by  streets  in  the  rectangular  system. 

"  Formula  (C)  gives  only  2.82  per  cent  of  additional  building 
area  consumed  by  diagonals. 

"  Formula  (D)  gives  13  per  cent  as  the  increase  in  frontage  due 
to  diagonals,  and  it  has  been  shown  that  the  saving  of  distance 
varies  from  30  per  cent  to  nothing. 

"  The  number  of  people  displaced,  which  is  only  2.82  per  cent,, 
will  be  abundantly  provided  for  by  the  additional  frontage  on  the 
diagonals,  revenues  will  be  augmented  by  assessments  on  the  new 
buildings  erected,  and  a  large  saving  will  be  effected  in  time  and 
distance  for  a  majority  of  the  inhabitants  by  this  combination  ci 
systems,  which  is  therefore  found  to  fulfil  the  requirement?  of 
practice  more  fully  than  any  other. 

"  Similar  applications  of  the  above  formula  will  show  to  what 
extent  the  plans  of  cities  already  established  or  to  be  built  may  be 


CITY   STREETS. 


505 


ULJULJl  _  ll_iUUl_r 


DDDnCDDODDC 


FiG,  142.     ARRANGEMENT  OF  STREETS  (PART  OF 
WASHINGTON,  D.  C.) 


506  HIGHWAY   COKSTRUCTIOISr. 

improved  by  the  opening  of  diagonals;  the  most  economical  relation 
of  street  to  building  area,  the  proper  distribution  of  the  street  area, 
and,  by  extending  the  analysis,  the  ratio  of  pavement  to  carriageway 
may  also  be  readily  determined.  All  of  these  questions  have  a 
direct  bearing  on  the  convenience,  health,  and  extension  of  our 
cities." 

Fig.  142  shows  the  system  adopted  in  laying  out  the  streets  of 
Washington,  D.  C. 

747.  Width  of  Streets. — The  width  of  streets  should  be  propor- 
tioned to  the  character  of  the  traffic  that  will  use  them ;  but,  as  a 
rule,  this  has  not  been  considered  in  the  laying  out  of  cities,  and 
the  width  of  the  commercial  thoroughfares  is  now  found  insufficient 
to  properly  accommodate  the  traffic. 

No  rule  can  be  laid  down  by  which  to  determine  the  best  width 
of  streets;  but  it  may  be  safely  said  that  a  street  which  is  likely  to 
become  a  commercial  thoroughfare  should  have  a  width  of  not  less 
than  120  feet  between  the  building  lines — the  carriage-way  80  feet 
wide,  and  the  sidewalks  20  feet  each. 

In  streets  occupied  entirely  by  residences  a  carriage-way  32  feet 
•wide  will  be  ample,  but  the  width  between  the  building  lines  may 
be  as  great  as  desired.  The  sidewalks  may  be  any  amount  over  10 
feet  which  the  fancy  may  dictate.  Whatever  width  is  adopted  for 
them,  not  more  of  it  than  8  feet  need  be  paved,  the  remainder 
being  occupied  with  grass  and  trees. 

Wide  streets  add  materially  to  the  commercial  prosperity  of  the 
inhabitants  of  a  city  by  relieving  them  of  the  heavy  tax  imposed 
by  narrow  streets  on  transportation  through  constantly  recurring 
blockades. 

Wide  streets  afford  a  good  amount  of  breathing  space,  and  thus 
add  to  the  general  health  of  the  people.  Moreover,  they  contribute 
to  a  city  an  air  of  spacious  comfort  and  dignified  distance,  and 
for  all  time  remove  from  it  the  crowded  appearance  which  is  too 
commonly  found  in  all  old  cities  and  towns. 

748.  The  maximum  and  minimum  width  of  streets,  with  the 
average  width  of  sidewalks  and  maximum  grade,  as  at  present  es- 
tablished in  various  cities,  are  given  in  Table  LXXXII. 

749.  Street  Grades. — Following  the  location  of  streets,  there  is 
the   important  duty  of   establishing  a  comprehensive   system  of 
grades.     If  this  could  always  be  done  in  advance  of  improvements, 


CITY   STKEETS.  50' 


there  would  be  little  difficulty  in  obtaining  the  best  grades  for  a 
city.  Unfortunately  this  is  seldom  the  case,  and  in  adjusting  the 
street  grades  of  villages  in  process  of  transformation  into  towns  the 
engineer  encounters  one  of  his  most  trying  duties;  he  meets  much 
opposition  from  the  property-owners  who  have  made  improvements 
based  upon  the  natural  slopes,  also  from  those  who  object  to  having  a 
street  in  excavation  where  it  passes  through  their  lands.  Each  one 
is  looking  to  his  individual  interest,  and  he  must  exercise  much  dis- 
cretion and  endeavor  to  fix  a  system  of  grades  harmonious,  conven- 
ient, and  economical  for  the  public  rather  than  for  individuals. 

Every  town  that  expects  to  thrive  should  at  a  very  early  stage  in 
its  history  establish  the  grades  of  its  streets  to  the  full  extent  of 
the  town  plot,  and  in  doing  so  keep  in  view  the  probability  of 
future  extension.  In  new  towns  this  ought  to  be  done  when  the 
town  is  laid  out,  and  the  grades  might  be  made  part  of  the  original 
record. 

750.  No  rule  can  be  laid  down  for  determining  the  proper 
grades  for  city  streets.     They  will  depend  upon  the  topographical 
features  of  the  site.    The  necessity  of  avoiding  deep  cuttings  or  high 
embankments  which  would  seriously  affect  the  value  of  adjoining 
property  for  building  purposes  often  demands  steeper  grades  than 
are  permissible  on  country  roads.    There  are,  however,  certain  con- 
ditions which  it  is  important  to  attain:  first,  that  the  longitudinal 
crown  level  be  uniformly  sustained  from  street  to  street  whenever 
practicable,  so  as  to  avoid  undulations ;  second,  that  the  crown  level 
at  all  intersections  be  extended  transversely  to  avoid  the  necessity  of 
driving  over  a  channel,  which  is  otherwise  formed. 

Table  LXXXII  shows  the  maximum  grade  of  streets  in  several 
cities. 

751.  The  best  arrangement  of  intersections   of  streets   when 
either  or  both  have  much  inclination  is  a  matter  requiring  much 
consideration  and  is  one  upon  which  much  diversity  of  opinion 
exists.     No  hard  or  fast  rule  can  be  laid  down;  each  will  require 
special  adjustment.     The  best  and  simplest  method  is  to  make  the 
rectangular  space  aaaaaaaa,  Fig.  143,  level  with  a  rise  of  one-half 
inch  in  10  feet  from  AAAA  to  B,  placing  gulleys  at  AAAA  and  the 
catch-basins  at  cccc.     When  this  method  is  not  practicable,  adopt 
such  a  grade  (but  one  not  exceeding  2|  per  cent)  that  the  rectangle 
AAAA,  Fig.  143,  shall  appear  to  be  nearly  level ;  but  to  secure  this 


508 


HIGHWAY   CONSTRUCTION. 


TABLE  LXXXII. 
WIDTH  OF  CITY  STREETS. 


City  of 

Width  of  Streets 
between  Building  Lines. 

Maximum 
Grade. 
Feet  per 
100  feet. 

Average  Width  of 
Sidewalks. 
Feet. 

Maximum. 
Feet. 

Minimum. 
Feet. 

New  York  N  Y 

100 
100 
100 
120 
100 
90 

100 
100 
70 
102 
150 
100 
80 
100 
132 
80 
120 
99 
118 
120 
104 
60 
160 
99 
120 
120 
100 
100 
120 
225 
65 
70 
160 
100 
120 
100 
200 
120 

m 

132 
132 
99 
99 
100 
80 
80 

60 
60 
40 
33 
33 
20 

50 
20 
30 
26 
30 
30 
30 
26 
40 
30 
40 
50 
30 
40 
20 
40 
.     80 
30 
60 
30 
30 
50 
20 
10 
20 
25 
28 
40 
36 
50 
50 
60 
40 
50 
60 
28 
49* 
60 
12 
15 

13 
12 

7 
20 
5 

8 

17.21 
20 
16 
11.66 
2.40 
4.80 
14 
3 
10 
8 
17 
5 
3 
15 
11 

9 

16 

15| 

7 
19 
10 
6 
13 
12 
5 
12 

15 
12.38 
10.70 
10 
9 
4 
9 

15 
18 
23 

14 

7 
8 
17 
14 
8 
25  to  4 

15 
10 
16  to  ft 

13 
17 

17 
16  to  8 

f  width  of  stL 
20  to  12 

£  width  of  sL 

i       „        .. 

6  to  4 
6 
20  to  8 
20  toO 
12  to  4 

27 
16 
20  to  6 
16  to  10 

12  to  6 
25  to  12 
15  to  3 
8 

Brooklyn  NY     

Buffalo   N  Y  

Elmira  NY            ... 

Schenectady,  N.  Y  

Lynn  ,  Mass  

Worcester  Mass  

Chicago   111          

Bloomiugton   111  

Jersey  City,  N  J  

Camdeu   N  J   ...»     .. 

Newark  N  J    

Trenton    N  J    

Terre  Haute  Ind  

Richmond  Va  

Omaha  Neb 

Nashville  Tenn 

Parkersburg  W   Va 

Washington    D   C  

"Wilmington   N   C 

Seattle  Wash     

Philadelphia,  Pa  

Pittsburg  Pa 

Ede  Pa              

Providence    K  It... 

Cumberland   Md  

Hartford   Conn  

"Waterbui'Y    Conn 

New  Haven    Conn    

Detroit   Mich  

Grand  Rapids  Mich  .    . 

St   Paul   Minn      

Minneapolis  Minn  

Salt  Lake  City  Utah   .  .    . 

Ogden   Utah    

Rutland  Vt       

Milwaukee,  Wis  

*  London    Eng     •  .  .  • 

*  Birmingham   Eng  

*  Foreign  cities  for  comparison. 


CITY    STKEETS. 


509 


WIDTH  OF  CITY  STREETS — Continued. 


Feet. 


Paris 


Berlin  :  TJnter  den  Linden 196 

Leipziger  Strasse 72 

Konig  Strasse 57 

Brussels:  Le  Boulevard  Circulaire 220 

Le  Boulevard  Ansbach 91 

Le  Rue  Royale 65 

Rue  de  Rivoli 88 

Grands  Boulevards 114 

Avenue  des  Champs  £lysees 229 

Avenue  Bois  de  Boulogne 393 

Vienna  :  Ringstrasse 187 

Hauptstrasse 

it  must  actually  have  a  considerable  dip  in  the  direction  of  the  slope 
of  the  street.  If  steep  grades  are  continued  across  intersections, 
they  introduce  side  slopes  in  the  streets  thus  crossed,  which  are 
troublesome,  if  not  dangerous,  to  vehicles  turning  the  corners,  es- 
pecially the  upper  ones.  Such  intersections  are  especially  objection- 
able in  rainy  weather.  The  storm  water  will  fall  to  the  lowest  point, 
concentrating  a  large  quantity  of  water  at  two  receiving-basins, 
which  with  a  broken  grade  could  be  divided  between  four  or  more 
basins. 


a a 

\  A 

\  / 

XBX 


A  Ap-J, 

a- a 


FIG.  143.    ADJUSTMENT  OF   GRADES  AT   STREET- 
INTERSECTIONS. 

752.  Fig.  144  shows  the  arrangement  of  intersections  on  steep 
grades  proposed  by  Messrs.  Rudolph  Hering  and  Andrew  Rosewater 
for  the  streets  of  Duluth,  Minn.  From  this  it  will  be  seen  that  at 


510 


HIGHWAY    CONSTRUCTION. 


these  intersections  the  grades  are  flattened  to  three  per  cent  for  the 
width  of  the  roadway  of  the  intersecting  streets,  and  that  the  grade  of 
the  curbs  is  flattened  to  eight  per  cent  for  the  width  of  the  inter- 
secting sidewalks.  Grades  of  less  amount  on  roadway  or  sidewalk 
are  continuous.  The  elevation  of  block-corners  is  found  by  adding 
together  the  curb  elevation  at  the  points  facing  the  block-corner, 
and  also  the  sum  of  the  widths  of  the  two  sidewalks  at  the  corner 
multiplied  by  two  and  one  half  per  cent,  and  dividing  the  whole  by 
two.  This  gives  an  elevation  equal  to  the  average  elevation  of  the 
curbs  opposite  the  corner  plus  an  average  rise  of  two  and  one  half 
per  cent  across  the  width  of  the  sidewalk. 

.*.  * 


300 


300 


6% 


!L_JSK  * 

w                                                                                                                                                      * 

3  JSwO: 

^n  i/\ 

i  ¥  1 

/0.3                                                                 ZS.7Z\ 

300 

RgM 

l&JtlL 

n fr 


753.  The  instructions  of  the  Department  of  Public  Works  of 
New  York  contain  the  following  directions  for  regulating  grades  at 
street-intersections : 

"  In  calculating  the  grades  from  the  centre  of  the  intersection 
to  the  circular  corners  or  curb-lines,  they  will  be  established  as 
follows :  In  the  avenues  when  the  ascents  and  descents  of  the  cross 


CITY    STREETS.  511 


intersecting  streets  exceed  1  inch,  in  10  feet,  the  grade  will  be  cal- 
culated at  1  inch  in  10  feet  to  the  curb-line  from  the  centre,  mak- 
ing 6  inches  difference  in  the  curbs  on  opposite  sides  of  the  avenues, 
and  the  slopes  up  and  down  the  avenues  will  be  calculated  accord- 
ing to  the  grade  of  the  avenue,  let  the  same  be  more  or  less." 

"  Apexes  and  punch-bowls  to  be  set  into  the  curb-line  at  the 
same  height  as  the  centre  grade." 

754.  Accommodation  summits  have  to  be  introduced  between 
street-intersections,  first  in  hilly  localities  to  avoid  excessive  excava- 
tion, and  second  when  the  intersecting  streets  are  level  or  nearly 
so,  for  the  purpose  of  obtaining  the  fall  necessary  for  surface- 
drainage. 

The  elevation  and  location  of  these  summits  may  be  calculated 
as  follows :  Let  A  be  the  elevation  of  the  highest  corner,  B  the 
elevation  of  the  lowest  corner,  D  the  distance  from  corner  to  corner, 
and  R  the  rate  of  the  accommodation  grade.  The  elevation  of  the 
summit  is  equal  to 

D.R  +  A  +  B 
2 

The  distance  from  A  or  B  is  found  by  subtracting  the  elevation  of 
either  A  or  B  from  this  quotient  and  dividing  the  result  by  the  rate 
of  grade.  Or  the  summits  may  be  located  mechanically  by  specially 
prepared  scales.  Prepare  two  scales  divided  to  correspond  to  the 
rate  of  grade — that  is,  if  the  rate  of  grade  be  one  foot  per  hundred 
feet,  then  one  division  of  the  scale  should  equal  100  feet  on  the 
map  scale.  These  divisions  may  be  subdivided  into  tenths.  One 
scale  should  read  from  right  to  left,  and  one  from  left  to  right. 

To  use  the  scales,  place  them  on  the  map  so  that  their  figures 
correspond  with  the  corner  elevations;  then  as  the  scales  read  in 
opposite  directions  there  is  of  course  some  point  at  which  the  op- 
posite readings  will  be  the  same :  this  point  is  the  location  of  the 
summits,  and  the  figures  read  off  the  scale  its  elevation.  If  the  dif- 
ference in  elevation  of  the  corners  is  such  as  not  to  require  an  in- 
termediate summit  for  drainage,  it  will  be  apparent  as  soon  as  the 
scales  are  placed  in  position. 

755.  Sufficient  fall  for  surface  drainage  may  be  secured  without 
the  aid  of  accommodation  summits,  by  arranging  the  grades  as  shown 
in  Fig.  145.     The  curb  is  set  level  between  the  corners,  a  summit  is 


512 


HIGHWAY    CONSTRUCTION". 


formed  in  the  gutter,  and  receiving-basins  are  placed  at  the  centre 
and  each  corner. 

CDRB  _  {  _  LEVEL 
'  ---------  BOTTOM  ~bF~Gl/f  f  ER  ---  .....  , 


SHOWING  CROWN  IN  STREET  GUTTER. 

756.  Transverse  Grade.  —  In  transverse  grade  the  street  should 
"be  level;  that  is,  the  curbs  on  opposite  sides  should  be  at  the  same 
level,  and  the  street  crown  rise  equally  from  each  side  to  the  centre. 
But  in  hill-side  streets  this  condition  cannot  always  be  fulfilled,  and 
opposite  sides  of  the  street  may  differ  as  much  as  five  feet  ;  in  such 
cases  the  engineer  will  have  to  use  his  discretion  as  to  whether  he 
will  adopt  a  straight  slope  inclining  to  the  lower  side,  thus  draining 
the  whole  street  by  the  lower  gutter,  or  adopt  the  three-curb 
method  and  sod  the  slope  of  the  higher  side. 

In  the  improvement  of  old  streets  with  the  sides  at  different 
levels  much  difficulty  will  be  met,  especially  where  shade-trees  have 
to  be  spared.  In  such  cases  recognized  methods  have  to  be  aban- 
doned, and  the  engineer  will  have  to  adopt  methods  of  overcoming 
the  difficulties  in  accordance  with  the  condition  and  necessities  of 
each  particular  case. 

As  an  example  of  what  may  be  done  in  such  cases  the  methods 
adopted  by  Mr.  J.  T.  Desmond,  City  Engineer  of  Haverhill,  Mass., 
may  be  cited. 

In  Fig.  146  is  shown  a  street  66  feet  wide,  with  one  sidewalk 


Fig.  146. 


Fig.   147. 


CITY   STREETS.  513 


5  feet  higher  than  the  other.  In  order  to  get  a  fair  cross-section  a 
third  line  of  curbing  was  put  in  at  the  crest  of  the  slope,  and  the 
slope  between  the  two  curbs  sodded.  This  produces  a  very  pleasing 
effect. 

In  Fig.  147  the  same  conditions  exist,  but  only  two  lines  of  curb- 
ing are  used,  the  slope  being  sodded  in  the  same  manner  as  in  the 
first  case. 

Again,  it  often  happens  that  two  parallel  streets  are  laid  out 
with  sharp  descending  grades,  and  later  on  the  city  is  called  upon 


SIDEWALK.O  ^•----^^^r^^':^ 


Fig.   148. 

ARRANGEMENT  OF  STREETS  WITH   OPPOSITE   SIDES 
AT  DIFFERENT   LEVELS. 

to  accept  a  new  street  laid  out  between  them.     The  method  shown 
in  Fig.  148  is  adopted. 

757.  Transverse  Contour. — The  most  suitable  form  of  transverse 
contour  and  proper  rise  for  each  kind  of  pavement  are  given  in 
Articles  618  and  619,  Chapter  XII. 

758.  Sub-foundation  Drainage  of  Streets. — The  sub-foundation 
drainage  of  streets  cannot  be  effected  by  transverse  drains,  because 
of  the  liability  of  their  disturbance  by  the  introduction  of  gas, 
water,  and  other  pipes. 

Longitudinal  drains  must  be  entirely  depended  upon;  they  may 
be  constructed  of  the  same  materials  and  in  the  same  manner  as 
road  drains.  The  number  of  these  longitudinal  drains  must  depend 
upon  the  character  of  the  soil:  if  moderately  retentive,  a  single  row 
of  tiles  or  a  hollow  invert  placed  under  the  sewer  in  the  centre  of 
the  street  will  generally  be  sufficient,  or  two  rows  of  tiles  may  be 
employed,  one  placed  at  each  curb-line ;  if  the  soil  be  exceedingly 
wet  and  the  street  very  wide,  four  or  more  lines  may  be  employed. 
These  drains  may  be  permitted  to  discharge  into  the  sewers 
of  the  transverse  streets  (Fig.  149.) 


514 


HIGHWAY   CONSTRUCTION. 


Fig.   149. 

SECTION  OF  SUBURBAN  STREET,  SHOWING  BROKEN- 
STONE  ROADWAY,  PAVED  GUTTER,  TILE-DRAIN,  AND 
GRAVEL  WALK. 

759.  Surface  Drainage. — The  removal  of  water  falling  on  the 
street  surface  is  provided  for  by  collecting  it  in  the  gutters,  from 
which  it  is  discharged  into  the  sewers  or  other  channels  by  means 
of  catch-basins  placed  at  all  street  intersections  and  dips  in  the 
street  grades. 

760.  Gutters. — The  gutters  must  be  of  sufficient  depth  to  retain 
all  the  water  which  reaches  them  and  prevent  its  overflowing  on 
the  footpath.     The  depth  should  never  be  less  than  6  inches,  and 
very  rarely  need  be  more  than  10  inches. 

In  streets  paved  with  granite,  wood,  and  brick,  gutters  are 
formed  of  the  same  material.  When  the  street  is  paved  with" 
asphalt  the  gutter  may  be  formed  either  of  asphalt,  recoated  with 
bitumen,  or  with  granite  blocks  or  gutter  stones.  The  width  of  this 
paving  need  not  exceed  12  inches. 

In  streets  where  broken  stone  is  used  the  gutters  may  be  formed 
with  gutter  stones  of  granite  blocks. 

761.  Catch-basins  are  of  various  forms,  usually  circular  or  rectan- 
gular, built  of  brick  masonry  coated  with  a  plaster  of  Portland 
cement.     Whichever  form  is  adopted,  they  should  fulfil  the  follow- 
ing conditions : 

(1)  The  inlet  and  outlet  to  have  sufficient  capacity  to  receive 
and  discharge  all  the  water  reaching  the  basin. 

(2)  Sufficient  capacity  below  the  outlet  to  retain  all  sand  and 
road  detritus,  and  prevent  it  being  carried  into  the  sewer. 

(3)  Trapped  so  as  to  prevent  the  escape  of  sewer-gas.     (This 


CITY   STREETS. 


515 


EXAMPLES  OF  CATCH-BASINS. 


SECTION. 


FIG.  150.     PLAN. 


516 


HIGHWAY   CONSTRUCTION. 


FIG.  151.    GUTTER    BASIN. 


FIG.  152.     CORNER   BASIN. 


FIG.  153.     EARTHENWARE    BASIN. 


CITY    STREETS.  517 


requirement  is  frequently  omitted,  to  the  detriment  of  the  health  of 
the  people.) 

(4)  Constructed  so  that  the  pit  may  be  easily  cleaned  out. 

(5)  Inlet  not  easily  choked  by  leaves  or  debris. 

(6)  Offer  the  least  possible  obstruction  to  the  traffic. 

(7)  The  pipe  connecting  the  basin  to  the  sewer  should  be  easily 
freed  of  any  obstruction. 

Figs.  150  to  153  show  various  forms  of  catch-basins. 

The  bottom  of  the  basins  should  be  6  or  8  feet  below  the  street 
level,  and  the  water  level  in  them  should  be  from  3  to  4  feet  lower 
than  the  street  surface,  as  a  protection  against  freezing.  The 
capacity  and  number  of  basins  will  depend  upon  the  area  of  sur- 
face which  they  drain. 

In  streets  having  level  or  light  longitudinal  grades  gullies  may 
be  formed  along  the  line  of  the  gutter  at  such  intervals  as  may  be 
found  necessary.  Catch-basins  are  usually  placed  at  the  curb-line 
of  the  street.  A  departure  from  this  practice  has  been  made  in  several 
cities,  notably  at  Providence,  R.  I.,  and  Rockford,  111.,  where  from 
two  to  six  inlets  are  placed  at  the  curb  line  of  the  corner  and  lead 
to  a  combined  basin  and  manhole  in  the  centre  of  the  street.  This 
reduces  the  cost  of  construction  and  of  cleaning,  and  removes 
from  the  sidewalk  the  dirty  operation  of  cleaning  the  basins. 

761a.  Catch-basins  and  gully-pits  require  to  be  cleaned  out  at 
frequent  intervals,  otherwise  the  odor  arising  from  the  decomposing 
matter  contained  in  them  will  be  very  offensive.  No  rule  can  be  laid 
down  for  the  intervals  at  which  the  cleaning  should  be  done,  but  they 
must  be  cleaned  often  enough  to  prevent  the  matter  in  them  from 
putrefying.  There  is  no  uniformity  of  practice  observed  by  cities 
in  this  matter;  in  some  the  cleansing  is  done  but  once  a  year,  in 
others  after  every  rain-storm,  in  still  others  at  intervals  of  three  or 
four  months,  while  in  a  few  they  are  cleaned  out  once  a  month. 

The  methods  employed  for  removing  the  silt  from  the  basins 
vary  greatly.  In  many  cities  the  matter  is  removed  by  ladling  it  out 
with  scoops,  hoes,  and  shovels;  in  a  few  a  laborer  enters  the  basin 
with  an  ordinary  bucket,  which  he  fills  with  the  silt,  while  another 
laborer  at  the  surface  hauls  it  up  and  empties  it  into  a  cart  or  into 
the  street-surface,  to  be  removed  later  on.  In  this  method  the  clean- 
ing gang  generally  consists  of  two  men  and  a  cart,  or  three  men  and 


518  HIGHWAY    CONSTRUCTION. 

two  carts,  and  from  six  to  twelve  basins  can  be  cleaned  per  day, 
depending  upon  the  amount  of  material  to  be  removed  and  the 
distance  to  the  place  of  disposal. 

In  many  cities  mechanical  appliances  are  employed  for  raising 
the  buckets  filled  with  silt.  These  consist  either  of  a  windlass,  a 
tripod  with  a  block  and  tackle,  or  a  block  and  tackle  suspended 
from  a  movable  arm  attached  to  the  body  of  the  wagon  used  for 
conveying  the  extracted  silt. 

In  Wilmington,  Del.,  the  basins  are  furnished  with  metal 
buckets  which  entirely  fill  the  space  below  the  outlet-pipe.  To 
clean  the  basin  the  bucket  is  hoisted  out  by  a  block  and  tackle 
suspended  from  a  tripod,  is  emptied,  and  returned  to  its  place  in 
the  basin. 

The  pneumatic  or  vacuum  system  of  removal  has  been  recently 
experimented  with  at  Columbus,  Boston,  and  other  cities,  and 
works  very  well  except  upon  basins  which  have  been  filled  with 
Tery  hard  material  from  macadamized  streets.  The  apparatus 
consists  of  a  large,  air-tight,  iron  tank,  mounted  on  a  wagon.  Two 
air-pumps,  driven  by  eccentrics  from  the  rear  axle,  are  connected 
with  the  tank,  and  as  the  wagon  is  driven  along  the  street  these 
pumps  exhaust  the  air  in  the  tank  and  produce  a  vacuum.  A 
5-inch  suction-hose,  the  end  of  which  has  a  bell-shaped  mouth,  is 
connected  with  the  tank  by  a  coupling  and  valve.  Upon  arriving 
at  the  catch-basin  to  be  cleaned,  the  suction-hose  is  inserted  in  the 
semi-liquid  mass,  the  valve  is  opened,  and  the  contents  of  the  catch- 
basin  are  drawn  into  the  tank.  This  operation  is  repeated  at  the 
different  catch-basins  until  the  tank  is  filled,  when  it  is  taken  to 
the  place  of  disposal.  During  the  whole  of  this  process  the  tank 
is  hermetically  sealed,  thus  preventing  the  escape  of  unpleasant 
odors. 

In  some  cities  the  cleaning  is  done  by  contract,  in  others  by 
the  employees  of  the  street-cleaning  department.  In  many  places 
the  cleaning  is  performed  in  the  most  perfunctory  manner;  in  others 
scrupulous  care  is  exercised,  the  walls  of  the  basin  being  washed 
and  scrubbed  with  a  broom,  water,  and  a  disinfectant. 

The  cost  of  cleaning  varies  greatly,  ranging  from,  twenty-five 
cents  to  five  dollars  per  cleaning. 


CITY   STREETS. 


519 


The  material  removed  from  the  basins  is  disposed  of  in  various 
ways.  In  New  York  it  is  sent  out  to  sea;  in  most  cities  it  is  used 
for  filling  in  low  lands. 


£*"   4      •  f 
<      -1  1C- 


FRONT  ELEVATION 


SECTION  ON  LINE  C-D 


SECTION  ON  LINE  A-B 
+  + 


PI 

DETAIL  OF  LIP 


FIG.  1 53A. 


Fig.  15  3#  illustrates  the  type  of  catch-basin  adopted  as  the 
standard  at  Columbus,  0.  The  sewer  connection  is  made  by 
means  of  a  15-inch  vitrified-pipe  drain,  terminating  in  a  vitrified 
special  elbow  of  the  form  shown.  This  elbow  gives  a  6-inch  seal 
when  the  basin  is  filled  to  the  flow-line  level.  A  removable,  lid  fit- 
ting over  a  6£-inch  hole  enables  the  pipe  to  be  inspected  and  cleaned 
if  necessary.  The  interior  of  the  basin  is  coated  with  an  eighth  of 
an  inch  coat  of  cement  mortar.  The  bill  of  material  for  a  standard 
catch-basin  of  the  dimensions  shown  is  as  follows:  excavation,  44 
cubic  yards;  brick,  900;  cement,  two  barrels;  sand,  1  cubic  yard; 
cast-iron  cover  and  lid,  340  pounds;  15-inch  vitrified  sewer-pipe 
and  special  elbow. 

The  manhole  cover  used  with  this  type  of  basin  has  a  32^-inch 


520 


HIGHWAY   CONSTRUCTION. 


top  with  projecting  piece  at  one  part  of  the  circumference.  This 
projection  forms  the  continuation  of  the  curb-line,  and  within  it  is 
the  street  inlet,  22£  inches  long  and  6J  inches  wide.  The  cover  is 
made  of  a  f-inch  top  plate  and  £-inch  sides  and  bottom  flange, 
The  lid  is  20  inches  in  diameter  and  made  of  f-inch  metal. 

762.  Surface  Drainage  at  Street  Intersections. — The  surface 
waters  should  not  be  carried  across  street  intersections  if  it  can  be 
possibly  avoided,  but  cases  may  arise  where  such  has  to  be  done, 


FlG.  153B.    SEWER    INLET   WITHOUT    BASIN. 

Where  it  is  necessary,  it  can  be  accomplished  as  shown  in  Figs.  154 
and  155. 

Waterways  formed  as  shown  in  Fig.  156  should  not  be  con- 
structed: they  are  a  nuisance,  and  an  obstacle  to  traffic. 

763.  Street  Lines  and  Monuments.— In  the  engineering  depart- 
ment of  every  city  there  should  be  adopted  and  carried  into  effect 
a  system  of  permanent  street  monuments,  whereby  the  street  lines 
may  be  accurately  relocated  at  any  time,  even  a  century  after  the 
original  survey  was  made.  In  the  absence  of  such  a  system,  it  is 


CITY    STREETS. 


521 


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CO 

«*'! 

UT 

e 


MOIH9 


CO 


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CL 
LO 


522 


HIGHWAY    CONSTRUCTION. 


impossible  to  accurately  retrace  the  original  survey.  With  the  im- 
provements continually  in  progress  old  landmarks  are  swept  away, 
and  the  reproduction  of  former  dines  is  largely  a  cut-and-try  pro- 
cess, involving  a  great  deal  of  work  which  is  productive  of  only 
approximate  results. 

The  remedy  lies  in  placing  at  all  street  corners  substantial  stone 
monuments,  and  protecting  them  by  special  ordinance  against  dis- 
turbance by  persons  excavating  in  the  streets. 

The  monuments  should  not  be  ~lel3  than  4  feet  long,  12  inches 
square  on  the  bottom,  and  6  inches  square  on  the  top;  the  top  sur- 
face and  4  inches  of  each  face  down  from  the  top  should  be  ham- 
mer-dressed. The  monuments'  should  be  set  with  the  upper  sur- 
face flush  with  the  surface  of  the  sidewalk  or  a  few  inches  below, 
but  so  placed  as  to  be  easy  of  access.  They  should  be  set  at  a  fixed 
distance  from  the  building  line — say  5  feet.  If  set  below  the  level  of 
the  footway  pavement,  a  hole  may  be  cut  in  the  pavement  and  closed 
with  a  cast-iron  frame  and  movable  cover  flush  with  the  surface  of 
the  pavement.  (See  Fig.  157.) 

The  intersections  of  the  lines  can  be  accurately  cut  upon  the 
top  surface,  or  a  small  hole  may  be  drilled  at  the  intersection  of  the 
lines,  filled  with  lead,  and  the  point  marked  with  a  centre-punch. 


maMmum*. 


FIG.  157.-SHOWING  MONUMENTS  AND  MANNER  OF 

PLACING. 

764.  Monuments. — For  defining  the  lines  of  country  roads. 
The  monuments  to  be  of  roughly  dressed  stone,  about  5  feet  long, 
16  inches  square  at  the  base  and  tapering  toward  the  top,  with  the 


CITY    STREETS.  523 


upper  foot  dressed  to  8  inches  square;  the  monument  to  be  set  in  a 
pit  3  feet  square  and  4J  feet  deep;  the  space  around  the  stone  to  be 
filled  with  small  stones,  gravel,  or  earth,  solidly  packed  in  thin 
layers.  The  top  of  each  stone  marked  with  its  diagonals,  and  its 
number  cut  on  one  of  the  faces  which  project  above  ground. 

765.  Street  Profiles. — The  following  instructions  of  the  Depart- 
ment of  Public  Works,  New  York,  in  regard  to  street  profiles  may 
be  useful. 

The  drawings  to  be  made  on  a  horizontal  scale  of  40  feet  and  a 
vertical  scale  of  8  feet  to  the  inch,  and  to  be  colored  and  figured  as 
hereinafter  indicated,  with  an  explanatory  legend. 

For  streets  60  feet  wide  and  under  there  will  be  three  profiles, 
one  on  each  side  and  one  intermediate  through  the  centre  of  the 
street,  to  be  shown  in  plan  and  elevation.  For  streets  more  "than 
€0  feet  wide,  two  additional  profiles  will  be  required,  one  through 
each  curb-  and  gutter-line  (to  be  drawn  in  plan  only,  not  in 
elevation) . 

The  established  grade-line  will  be  shown  on  the  elevation  only. 
Vertical  heights  above  the  high-water  line  will  be  given  at  least 
every  50  feet  for  the  established  grade-line  and  for  the  several 
lines  of  profile ;  the  former  on  the  elevation  and  the  latter  on  the 
plan. 

The  plan  will  be  drawn  below  the  profile. 

The  colors  used  will  be  as  follows : 

Line  of  high-water  (datum).. Blue 

Vertical  height-lines Black 

Established  grade-line. Red 

Natural  surface  as  follows: 

South  line  of  streets      )  Orange 

West  line  of  avenues     )  ' 

North  line  of  streets      )  ^  ^  .Green 

East  line  of  avenues       )  ' 

North  curb  of  streets     )  .  .Burnt.Sienna 

East  curb  of  avenues"  ~y^ 

South  curb-line  of  streets       )  Blue 

West  curb-line  of  avenues     f 

Rock  to  be  colored  with India  ink 

Earth  "          "    ......Orange 

Flagging         ••          "    Blue 


524 


HIGHWAY    CONSTRUCTION. 


O 


IT 
UJ 

z 
oc 
O 
O 


00 
10 


o 


CITY   STREETS.  525 


When  earth  and  rock  occur  the  surveyor  will  be  required  to 
designate  upon  the  original  plan  the  outline  of  the  intersection  of 
the  rock,  when  the  same  shall  be  developed  by  a  plan  parallel  to 
and  two  feet  below  the  established  grade. 

766.  Increasing  the  Width  of  the  Carriageway  at  Street-cross- 
ings. — Experience  has  proven  the  value  of  the  London  practice  of 
widening  the  carriageway  at  street-corners  and  the  providing  of 
refuges  or  resting-places  for  pedestrians.     Fig.  158  shows  a  typical 
street-corner,  and  Fig.  159  shows  the  widened  corner  and  refuges. 

Travel  is  always  slower  and  somewhat  congested  at  crossings, 
and  the  widening  of  the  wheelway  at  these  points  expedites  its 
movement;  while  the  refuges,  besides  keeping  the  traffic  on  its 
proper  side  of  the  street,  are  of  great  convenience  to  pedestrians 
crossing  the  street.  These  refuges  are  usually  4  feet  wide  and 
.about  12  feet  long,  and  are  elevated  above  the  street  surface;  they 
are  bordered  by  curb-stones,  and  in  the  centre  is  generally  an 
ornamental  lamp-post,  indicating  its  position  and  carrying  the  street 
signs. 

Another  consideration  in  favor  of  these  corners  is  the  oppor- 
tunity they  present  for  ornamental  facades,  that  add  to  the  beauty 
of  the  city. 

767.  Street  Statistics. — The  following  table  shows  the  length  of 
streets  for  each  of  fifty  of  the  largest  cities  in  the  United  States, 
with   the  amount  paved  and  unpaved,  the  number  of  miles  of 
streets  lined  with  shade-trees,  extent  of  grassed  places  or  parking 
-along  the  streets,  the  number  of  miles  of  streets  to  each  square 
mile  of  area,  the  percentage  of  street  area  to  the  area  of  the  city,  and 
tho  number  of  population  to  each  mile  of  streets  for  the  year  1890. 


'526 


HIGHWAY   CONSTRUCTION. 


TABLE  LXXXIII. 


Cities. 

Streets. 

Miles  of  Streets  Lined 
with  Shade  Trees. 

Grassed 
Places. 

Miles  of  Streets  to  each 
square  mile  of  Area. 

Per  cent  of  Street  Area 
to  City  Area. 

Number  of  Population 
to  each  mile  or  Streets. 

Length  in  miles. 

Per  cent  of 
Length  Paved. 

Length  (miles). 

Average  Width 

(feet). 

1 

Paved. 

3 
3-0 

||t 

263 

New  York,  N.  Y  
Chicago,  111  
Philadelphia,  Pa  
Brooklyn,  N.  Y  
St   Louis  Mo 

575 
2048 
1151 
653 
1061 

408 
780 
342 
486 
462 

372 
625 
400 
419 
235 

186 
800 
508 
240 
970 

756 
400 
195 
438 
140 

105 
251 
106 
79 
100 

100 
125 
130 
136 
800 

82 
30 
529 
340 
56 

50 
80 
224 
90 
140 

150 
200 
125 
30 
1*0 

358 
629 
750 
375 

422 

408 
459 
92 
254 
69 

194 
89 
147 
72 
163 

48 
25 
52 
72 
40 

'234' 
195 
60 
32 

19 
147 
2 
23 
31 

7 
82 
80 
33 
83 

75 
17 
25 
14 
9 

50 
4 
35 
43 
26 

5 
170 
15 
27 
31 

45 
1419 
50 
3 
40 

"lOO" 
190 

i29' 
"26i" 

'"e 

138 
4 
41 
72 
325 

756 
16 

'220 

1 
'79 
'20 

50 
30 
50 
52 
76 

"  3' 
66 
75 
43 

"'76' 
20 
5 
79 

115 
20 
110 
3 

50 

62.26 
30.71 
65.16 
57.43 
39.77 

100.00 
58.85 
26.90 
52.26 
14.91 

52.15 
14.24 
36.75 
17.18 
69.  30 

25.81 
3.13 
10.24 
30.00 
4.12 

1266' 

'iss' 

50 

"ioo" 

isoo' 

'306 
30 

•••7- 
'"5" 

10 

14.30 
12.75 
8.90 
24.68 
17.29 

11.56 
27.48 
22.12 
19.44 
18.57 

9.53 
16.85 
19.43 
24.65 
22.95 

10.47 
15.48 
20.73 
15.38 
lb.86 

48.81 
39.72 
5.73 
22.21 
18.52 

9.42 
29  74 
9.68 
13.55 
23.04 

25.32 
11.75 

8.77 
30.77 
28.99 

12.29 
20.41 
68.88 
11.00 
22.31 

12.56 
7.97 
69.  35 
20.2^ 
31.75 

22.  OC 
4.2* 
15.2* 
25.  (K 
18.84 

16.25 
15.94 
8.42 
32.72 
19.65 

8.76 
34.36 
28.91 
18.41 
23.21 

10.47 
19.15 
20.97 
35.01 
43.46 

11.89 
23.46 
25.92 
14.57 
21.44 

73.95 
56.42 
5.43 
27.76 
21.04 

8.92 

28.16 
9.17 
12.83 
26.18 

28.77 
11.13 
11.76 
40.79 
32.94 

11.64 
22.42 
78.27 
16.67 
21.13 

14.28 
7.55 
86.69 
21.0" 
42.09 

25.0" 
3.20 
19.0 
31.2 
23.5 

2,635.31 
537.03 
909.61 
1,234.83 
425.80 

1,099.21 
556.97 
874.26 
610.92 
565.70 

687.27 
387.26 
514.69 
487.99 
863.74 

977.58 
205.94 
276.48 
557.90- 

137.27 

141.15 
263.59 
434.13 
185.  9? 
580.70 

739.96- 
303.46- 
701.87 
886.  43- 
583.13 

574.58 
445.82- 
409.46 
373.21 
62.99 

544.  56. 
1,454.93- 
71.96- 
111.19 
650.45 

712.74 
437.56- 
147.83 
330.09 
191.94 

174.59 
127.24 
200.72 
830.60 
196.53 

Boston    Mass     

Baltimore,  Md  
San  Francisco,  Cal.  .. 
Cincinnati,  Ohio  
Cleveland,  Ohio  

Buffalo   N  Y 

200 
25 

349 

230 

"  50' 

350 
30 
360 

"2-30 

'466' 
10 

"28" 

10 
30 
15 

"'26' 

"'4' 

6 
"'36' 

New  Orleans,  La  
Detroit    Mich     

Milwaukee,  Wis.  .  .   . 
Washington,  D.  C.  .. 

Newark,  N.  J  

Minneapolis,  Minn.. 

Rochester,  N.  Y  
St.  Paul,  Minn  

Denver,  Col  
Indianapolis,  Ind  — 
Worcester,  Mass  
Toledo  Ohio 

58.50 
100.00 
13.70 
22.86 

18.10 
58.57 
1.89 
29.11 
31.00 

7.00 
65.60 
61.54 
24.26 
10.38 

91.46 
56.67 
4.73 
4.12 
16.07 

100.00 
5.00 
15.63 
47.78 
18.57 

3.33 

85.00 
12.00 
90.00 
25.  83 

234 
150 
70 

79 
50 

234 

6 

25 

12 

New  Haven,  Conu  .  .  . 

Lowell,  Mass  
Nashville,  Tenn  
Fall  River,  Mass  
Cambridge,  Mass  .  .  . 
Camuen   N.  J  

150 

20 

'56' 

75 
20 
91 
6 

"'9' 
15 
45 

49 

'"56 

'45 
30 

150 

"20 
25 
60 

"  i' 

5 

"gf 
1 

80 

'  '  '20 
5 

'"l5 
12 
30 

Trenton,  N.  J.  .  .  .   ... 

Lynn   Mass        ... 

Hartford,  Conn  
Evansville,  Ind  
Los  Angeles,  Cal  

Lawrence,  Mass  
Hoboken,  N.  J.  
Dallas,  Tex  
Sioux  City,  Iowa.... 
Portland,  Me  

15 

90 
3 

12 
50 
23 
85 
5 

16 

20 
2 

98 

2 
8 
10 

4 
4 
10 
6 
6 

8 
7 
"5 

Holyoke,  Mass  
Binght  niton,  N.  Y.. 
Duluth,  Minn 

Elmira  N  Y 

Davenport,  Iowa  .  .  . 
Canton    Ohio 

Taunton,  Mass  
Lacrosse,  Wis  

Newport.  Ky  
Rockford,  111  

CHAPTER  XVII. 
FOOTPATHS,  CURBS,  GUTTERS. 

768.  A  FOOTPATH  or  walk  is  simply  a  road  under  another  name, 
a  road  for  pedestrians  instead  of  one  for  horses  and  vehicles.     The 
only  difference  that  exists  is  in  the  degree  of  service  required;  but 
the  conditions  of  construction  that  render  a  road  well  adapted  to 
its  object  are  very  much  the  same  as  those  required  for  a  walk. 

The  effects  of  heavy  loads  such  as  use  carriageways  are  not 
felt  upon  footpaths,  but  the  destructive  action  of  water  and  frost  is 
the  same  in  either  case,  and  the  treatment  to  counteract  or  resist 
these  elements  as  far  as  practicable  and  produce  permanency  must 
be  the  controlling  idea  in  each  case,  and  should  be  carried  out 
upon  a  common  principle.  It  is  not  less  essential  that  a  walk 
should  be  well  adapted  to  its  object  than  that  a  road  should  be, 
and  it  is  annoying  to  find  it  impassable  or  insecure  and  in  want  of 
repair  when  it  is  needed  for  convenience  or  pleasure.  In  point 
of  economy  there  is  the  same  advantage  in  constructing  a  footway 
skilfully  and  durably  as  there  is  in  the  case  of  a  road. 

769.  Width. — The  width  of  footwalks  (exclusive  of  the  space 
occupied  by  projections  and  shade-trees)  should  be  ample  to  com- 
fortably accommodate  the  number  of  people  using  them.   In  streets 
devoted  entirely  to  commercial  purposes  the  clear  width  should  be 
at  least  one  third  the  width  of  the  carriageway;  in  residential  and 
suburban  streets  a  very  pleasing  result  may  be  obtained  by  making 
the  walks  one  half  the  width  of  the  roadway  and  devoting  the 
greater  part  to  grass  and  shade  trees. 

The  width  adopted  for  sidewalks  in  several  cities  is  given  in 
Table  LXXXII,  page  388. 

770.  Cross-slope. — The  surface  of  footpaths  must  be  sloped  so 
that  the  surface-water  may  readily  flow  to  the  gutters.    This  slope 

527 


528  HIGHWAY   CONSTRUCTION".  ' 

need  not  be  very  great;  £  inch  per  foot  will  be  sufficient.  A 
greater  slope  with  a  thin  coating  of  ice  upon  it  becomes  dangerous 
to  pedestrians. 

771.  Foundation. — As  in  the  case  of  roadways  so  with  foot- 
paths, the  foundation  is  of  primary  importance.   Whatever  material 
may  be  used  for  the  surface,  if  the  foundation  is  weak  and  yielding 
the  surface  will  settle  irregularly  and  become  extremely  objection- 
able, if  not  dangerous,  to  pedestrians. 

772.  Surface. — The  requirements  of  a  good  covering  for  side- 
walks are : 

(1)  It  must  be  smooth  but  not  slippery. 

(2)  It  must  absorb  the  minimum  amount  of  water,  so  that  it 
may  dry  rapidly  after  rain. 

(3)  It  must  not  be  easily  abraded. 

(4)  It  must  be  of  a  uniform  quality  throughout,  so  that  it  may 
wear  evenly. 

(5)  It  must  neither  scale  nor  flake. 

(6)  Its  texture  must  be  such  that  dust  will  not  adhere  to  it. 

(7)  It  must  be  durable. 

773.  Materials. — The  materials  used  for  footpaths  are  as  fol- 
lows: stone  natural  and  artificial,  wood,  asphalt,  brick,  tar  con- 
crete, and  gravel. 

774.  Of  the  natural  stones,  sandstone  (bluestone)  and  granite 
are  extensively  employed.  . 

The  bluestone  when  well  laid  forms  an  excellent  paving  mate- 
rial. It  is  of  compact  texture,  absorbs  water  to  a  very  limited  extent, 
and  hence  soon  dries  after  rain;  it  has  sufficient  hardness  to  resist 
abrasion,  and  wears  well  without  becoming  excessively  slippery.  It 
can  be  obtained  in  flags  of  almost  any  size  and  thickness.  As  found 
in  the  quarries,  the  layers  of  stone  range  from  1  inch  to  3  feet  in 
thickness,  the  top  beds  being  usually  the  thinner.  The  size  of  the 
blocks  in  superficial  area  varies;  frequently  blocks  60  feet  long  by 
20  feet  wide  and  10  inches  thick  are  lifted  from  the  bed.  The 
largest  slab  as  yet  brought  to  tide-water  was  20  X  24  feet  and  10 
inches  thick,  and  there  are  slabs  used  for  flagging  in  New  York  15 
by  20  feet  by  8  inches. 

Granite,  although  exceedingly  durable,  wears  very  slippery  and 
its  surface  has  to  be  frequently  roughened. 

775.  Slabs  of  whatever    stone    must  be  of    equal  thickness 


FOOTPATHS,  CURBS,  GUTTERS.  520 

throughout  their  entire  area;  the  edges  must  be  dressed  true  to  the 
square  for  the  whole  thickness  (edges  must  not  be  left  feathered  as 


FIG.    160.      IMPROPER    MANNER    OF    DRESSING    THE 
EDGES  OF  CROSSING-STONES  AND   FLAGSTONES. 

shown  in  Fig.  160) ;  and  they  must  be  solidly  bedded  on  the  foun- 
dation and  the  joints  filled  with  cement-mortar. 

Badly  set  or  faultily  dressed  flagstones  are  very  unpleasant  to 
walk  over,  especially  in  rainy  weather;  the  unevenness  causes 
pedestrians  to  stumble,  and  rocking  stones  squirt  dirty  water  over 
their  clothes. 

776.  Specifications  for    Flagstones,   (New    York).— Flagstones 
shall  be  of  the  best  quality  of  North  Elver  bluestone,  4  feet  wide, 
not  less  than  3  inches  thick,  and  to  contain  not  less  than  12  super- 
ficial feet.    The  edge  shall  be  dressed  the  whole  depth  of  the  stone, 
so  as  to  lay  close  joints,  and  the  top  shall  be  cut  evenly,  so  as  to 
leave  no  depressions.     Flagging  shall  be  laid  in  four  inches  of  sand 
or  clean  gritty  earth,  and  the  joints  closed  with  cement-mortar. 

777.  Wood  has  been  largely  used  in  the  form  of  planks;  it  is 
cheap  in  first  cost,  but  proves  very  expensive  from  the  fact  that  it 
lasts  but  a  comparatively  short  time  and  requires  constant  repair  to 
keep  it  from  becoming  dangerous. 

778.  Asphalt  forms  an  excellent  footway  pavement;  it  is  dur- 
able and  does  not  wear  slippery.     It  is  largely  employed  for  this 
purpose  in  Europe. 

The  proportions  of  materials  employed  in  Paris  are  given  as 
follows : 

Bituminous  rock 1456  pounds 

Bitumen 68 

Sand 784      " 

This  requires  about  225  pounds  of  coal  to  heat  it,  and  one  work- 
man can  prepare  3  tons  of  material  in  12  hours. 

The  following  table  gives  the  number  of  square  yards  that  a  ton 
of  prepared  rock-asphalt  will  spread : 


530 


HIGHWAY    CONSTRUCTION. 


TABLE  LXXXIV. 


With  about 

Without  Grit. 
Square  yards. 

25  per  cent  of 
Grit. 
Square  yards. 

Thickness. 
Inches. 

63 

80 

1 

51 

65 

32 

40 

I 

26 

33 

1 

16 

20 

4 

18* 

16 

2 

A  skilled  workman  properly  assisted  can  lay  140  to  180  square- 
yards  in  a  day. 

779.  The  life  of  asphalt  footways  may  be  taken  at  about  twelve 
years  under  ordinary  traffic.    The  concrete  will  remain  untouched, 
and  what  is  left  of  the  asphalt  may  be  remelted,  so  that  a  renewal 
is  not  so  costly  as  the  first  expense. 

Compressed-asphalt  paths  have  lasted  ten  years  in  some  of  the 
busiest  thoroughfares  of  London.  In  Leicester,  uncompressed- 
asphalt  paths  have  lasted  fifteen  years  under  considerable  traffic. 

The  thickness  of  the  asphalt  should  not  be  less  than  one  inch. 

780.  Specifications  for  Sheet-asphalt  Footway  Pavements  (Wash- 
ington, B.C.) 

Grading. — The  space  over  which  the  sidewalk  is  to  be  laid  will 
be  graded  to  a  depth  of  3  inches  below  the  finished  surface  of  the 
pavement.  Soft  and  spongy  places  not  affording  a  firm  foundation 
will  be  removed  and  good,  clean  gravel  substituted  therefor.  The 
bed  thus  prepared  will  be  thoroughly  rolled  and  rammed  to  the 
satisfaction  of  the  Engineer  or  his  authorized  representative. 

Tree-spaces. — A  space  of  such  dimensions  as  may  be  directed 
by  the  Engineer  Commissioner  (usually  2  by  4  feet)  will  be  left 
around  each  tree.  Around  the  edges  of  this  space  will  be  planted 
a  framework  of  Georgia  pine,  2  inches  in  thickness  and  9  inches  in 
depth.  The  plank  forming  the  rear  of  the  framework,  and  which 
is  parallel  to  the  curb,  will  be  firmly  nailed  to  the  other  two  pieces, 
and  will  be  cut  in  such  a  manner  that  it  will  bind  underneath  the 
pavement  to  be  laid,  so  that  the  top  edges  will  be  even  with  the 
pavement  when  completed.  In  the  spaces  between  the  framework 
and  the  sides  of  the  trench  coarse  sand  will  be  placed  and  com- 
pacted by  tamping  with  narrow  rammers  especially  constructed  for 


FOOTPATHS,  CURBS,  GUTTERS.  531 

this  purpose.  These  spaces  will  be  then  filled  to  the  sub-grade  of 
the  pavement,  and  the  tree-spaces  will  be  filled  with  earth  and  left 
in  a  neat  and  clean  condition. 

Base. — On  the  bed  prepared  as  above  specified  a  layer  of  clean 
broken  stone,  of  size  not  exceeding  £  inch  in  largest  dimen- 
sions, will  be  spread  to  a  depth  of  2f  inches.  This  will  be  com- 
pressed by  rolling  arid  tamping  to  a  thickness  of  2  inches.  On  this 
will  be  poured,  at  a  temperature  of  about  250  degrees  Fahr.,  the 
residuum  of  coal-tar  distillation  known  in  the  trade  as  No.  4  Paving 
Composition.  About  |  gallon  of  this  composition  will  be  used 
for  each  square  yard  of  pavement,  and  it  will  be  poured  on  the  base 
of  broken  stone  in  such  manner  as  to  thoroughly  coat  the  stones 
on  the  surface  and  fill  the  interstices  thereof. 

Wearing  Surface. — The  cementing  material  of  the  wearing 
surface  will  be  asphalt  paving-cement  prepared  from  the  best 
quality  of  Trinidad  asphalt,  obtained  from  the  so-called  Pitch  or 
Asphalt  Lake  in  the  island  of  Trinidad,  and  the  residuum  of 
petroleum  distillation,  mixed  in  the  proportions  of  about  six  parts 
of  refined  asphalt  and  one  part  of  residuum.  With  this  paving- 
cement  will  be  combined  the  old  asphalt  pavement  from  Penn- 
sylvania Avenue  or  elsewhere,  and  crushed  granular  limestone 
quartz  or  other  stone  of  a  white  color,  in  the  following  proportions : 

Old  pavement 69  to  76  per  cent 

Crushed  stone 26  to  15 

Asphalt  cement  as  above  specified 5  to    9       " 

100     100  per  cent 

The  old  pavement  will  be  furnished  by  the  District  at  the 
property  yards  near  the  foot  of  New  Hampshire  Avenue;  the  other 
materials  will  be  furnished  by  the  contractor.  The  crushed  stone 
in  the  wearing  surface  will  vary  in  size  from  £  of  an  inch  to  dust. 

The  asphalt  pavement  will  be  broken  into  pieces  not  exceeding 
4  inches  in  their  largest  dimensions,  and  will  then  be  mixed  with 
the  crushed  stone  in  the  proportion  of  about  4  parts  of  asphalt 
pavement  to  one  part  of  crushed  stone.  This  mixture  will  then  be 
heated  to  a  temperature  of  about  300  degrees  Fahr.  in  a  suitable 
apparatus,  and  thoroughly  mixed  and  made  homogeneous  by 
stirring,  special  care  being  taken  not  to  overheat  the  material  or 


532  HIGHWAY    CONSTRUCTION. 

'burn  the  asphalt.  During  the  progress  of  mixing,  asphalt  cement 
ivill  be  added  in  the  proportion  of  5  per  cent  to  9  per  cent  by 
•weight  of  the  mixture;  the  exact  proportion  of  asphalt  cement  thus 
to  be  added  for  the  purpose  of  enriching  the  old  pavement  will  be 
determined  by  the  Engineer  Commissioner. 

The  material  thus  prepared  will  be  brought  to  the  work  at  a 
temperature  of  250  degrees  to  275  degrees  Fahr.,  and  will  be  spread 
on  the  base  above  specified  by  means  of  hot  iron  rakes  to  a  thick- 
ness of  14^  inches,  and  will  then  be  compressed  by  rolling  and  ram- 
ming to  the  thickness  of  1  inch.  A  small  amount  of  hydraulic 
cement  will  then  be  spread  over  the  surface,  and  the  rolling  will 
l)e  continued  until  the  pavement  is  thoroughly  compressed.  Care 
shall  be  taken  at  all  times  not  to  interfere  with  business  or  travel 
more  than  is  absolutely  necessary  for  the  faithful  performance  of 
the  work.  During  the  time  that  travel  is  necessarily  closed  at  any 
point  the  contractor  shall  provide  temporary  walks,  said  walk  to  be 
at  all  times  in  condition  for  pedestrians,  and  easy  of  access  from 
adjoining  walks.  The  contractor  shall  remove  all  stone,  plank, 
ibrick,  or  other  material  of  value  from  points  where  the  sidewalks 
are  to  be  laid,  as  the  work  progresses,  and  shall  haul  them  to  the 
nearest  property  yards,  or  otherwise  dispose  of  them,  as  the  Engi- 
neer Commissioner  may  desire. 

Curb. — Whenever  ordered  the  curb  will  be  reset.  Curb  will  be 
redressed  by  the  contractor  whenever  ordered,  for  which  a  fair 
price,  to  be  fixed  by  the  Engineer  Commissioner,  will  be  paid. 

781.  Extracts  from  Specifications  for  Asphalt  Footway  Pave- 
ments (Paris). 

Form  and  Dimensions  of  Work. — Art.  7.  The  width  of  the 
sidewalks  for  each  locality  will  be  determined  by  the  administra- 
tion, its  slope  by  the  engineer.  The  curb  between  the  sidewalk 
and  the  roadway  will  not  be  included  in  this  contract. 

Art.  16.  The  mastic  pavements  will  be  formed  of  a  layer  of 
pure  asphaltic  mastic  at  least  -fv  inch  thick,  resting  on  a  bed  of 
Jiydraulic  concrete  4  inches  thick  which  comprises  a  covering  of 
hydraulic  mortar  at  least  f  inch  thick. 

Art.  17.  The  compressed-asphalt  pavements  will  consist  of  an 
upper  layer  of  compressed  asphalt  1|  to  2£  inches  thick,  resting  on 
a  foundation  of  hydraulic  lime  or  cement  concrete  4  to  G  inches 
thick,  covered  as  above  with  mortar,  or  upon  an  old  macadam  road- 


FOOTPATHS/  CURBS,  GUTTERS.  533 

way  picked  over  and  covered  with  a  thin  coat  of  hydraulic? 
mortar. 

Art.  2i.  The  asphaltic  mastic  employed  either  for  new  or  re- 
pairing o"!d  paving  shall  be  composed  of  naturally  impregnated 
rock  with  natural  bitumen  of  good  quality,  coming  exclusively 
from  mineral  rocks. 

The  fictitious  bitumens  extracted  by  the  purification  of  the 
heavy  oils  or  schists  and  by  the  distillation  of  coal,  also  the  so- 
called  fatty  bitumens,  and  all  other  analogous  products  shall  be 
rigorously  proscribed. 

The  rock  employed  after  being  reduced  to  powder  will  be 
melted  with  a  sufficient  quantity  of  purified  natural  bitumen  to* 
form  a  mastic  which,  when  cold,  presents  a  homologous  mass 
slightly  elastic  and  which  does  not  soften  under  a  hot  sun.  This, 
mastic  shall  be  moulded  into  blocks.  There  may  also  be  used  blocks 
of  bituminous  mastic  with  a  base  of  slates  manufactured  by  the 
process  of  M.  Sebille. 

Art.  22.  The  contractor  shall  be  bound  to  employ  under  the 
orders  of  the  engineers  upon  each  public  way  the  bituminous  mas- 
tic above  described. 

The  mastic  shall  be  formed  of  a  mixture  of  natural  bitumen,  in 
the  proportion  of  one  twelfth  of  its  weight  at  most,  and  the  calca- 
reous asphalt  rocks  of  Seyssel,  Seyssel-Forens,  Pyrimont  or  Vo- 
lants, of  Val  de  Travers  or  Lobsan,  or  others  deemed  equivalents 
by  the  engineers. 

The  mastic  having  a  base  of  slate  of  M.  Sebille  will  be  formed 
of  a  mixture  of  bitumen  described  in  Art.  23  following,  and  of 
powdered  red  or  blue  slate  of  Ardennes,  powdered  chalk  of  Men- 
don  or  of  Nanterre,  .and  of  silica  from  the  basin  of  Paris,  in  the 
following  proportions  by  weight : 

Refined  mineral  bitumen 30  parts. 

Ground  slate 35     " 

Powdered  chalk 10     "• 

Silica,  ground  and  sifted 25     "• 

100  parts 

Art.  23.  The  bitumen  shall  come  as  much  as  possible  from  the> 
weighings  of  bituminous  sandstone  or  the  asphaltic  rock  of  Maestu,. 
and  in  their  default  from  the  dry  pitch  of  Trinidad,  perfectly  puri— 


534  HIGHWAY    CONSTRUCTION. 

fied.  It  ought  to  be  viscid  at  the  ordinary  temperature,  never 
brittle  or  liquid;  drawn  into  threads  it  should  lengthen  and  only 
break  in  very  fine  points. 

Art.  24.  The  rock  employed  should  be  calcareous,  soft,  with 
fine  grain,  texture  fairly  compact,  regularly  impregnated  with 
bitumen  so  as  not  to  show  black  and  white  spots;  it  should  be  of  a 
brown  color;  heated  to  122  to  140  degrees  Fahr.  it  should  soften 
and  break  on  being  torn.  Care  must  be  taken  for  the  area  in 
asphalt  to  choose  only  such  pieces  as  are  of  the  most  even  grain 
and  richest  impregnation.  The  rock  of  Lobsan,  however,  should 
not  be  employed  alone  in  the  asphalt  roadways;  it  ought  to  be 
mixed  with  other  rocks  less  fat,  in  proportions  which  will  be  de- 
termined by  the  engineer  according  to  the  composition  of  the 
other  rocks.  It  should  contain  at  least  7  per  cent  of  bitumen  and 
at  the  most  93  per  cent  of  lime;  its  change  into  mastic  must  not 
require  more  than  9  per  cent  of  bitumen. 

Art.  25.  The  materials  entering  into  the  composition  of  the 
pavements  are  the  mastics  described  in  Art.  22;  pure  gravel  grit 
and  natural  bitumen  to  assist  the  melting.  These  materials  ought 
to  be  generally  employed  in  the  following  proportions  by  weight : 

f  Asphaltic  mastic 100 

Foot-pavements  with  a  base  of  asphalt  <  Bitumen 6 

'Grit 60 

C  Asphaltic  mastic 100 

Foot-pavements  with  a  base  of  slate —  <  Bitumen 7 

(Gravel 50 

Art.  26.  One  month  before  the  award  of  this  contract  the 
competitors  must  deposit  at  the  office  of  the  works  in  Paris  samples 
of,  1st,  a  block  of  the  mastic  described  above;  2d,  specimens 
of  the  asphaltic  rocks  and  the  natural  bitumens  they  intend  to 
use;  3d,  a  note  indicating  the  elements  of  the  composition  of 
the  mastics,  and  proportions  of  the  various  rocks  that  they  intend 
to  employ  in  the  composition  of  the  asphaltic  areas.  The  blocks 
and  specimens  of  rocks  and  bitumen  to  have  the  trade-marks  of 
the  works  from  whence  they  came  and  the  signatures  of  the  com- 
petitors. 

The  necessary  certificates  to  compete  for  the  contract  will  not 
be  delivered  till  after  the  examination  and  acceptance  by  the 
engineers  of  the  specimens  deposited.  During  all  the  term  of  this 


FOOTPATHS,  CURBS,  GUTTERS.  535 

•contract  the  contractor  can  only  use  materials  exactly  similar  to 
the  specimens  deposited. 

Art.  27  provides  for  continuous  inspection  of  the  contractor's 
works,  and  the  right  to  compel  the  contractor  to  manufacture  the 
mastics  in  the  depots  belonging  to  the  city. 

Art.  31.  The  lime  employed  is  to  be  hydraulic  lime  in  powder. 
It  must  be  brought  onto  the  works  in  sealed  bags  marked  with  the 
name  of  the  maker.  Only  the  lime  and  cement  designated  in  the 
.specifications  for  the  construction  and  repair  of  sewers  will  be 
.allowed. 

Art.  32.  The  broken  flint  must  pass  through  a  ring  of  2}  inches 
.and  be  at  least  f  inch  thick.  It  must  be  free  from  all  earthy 
matters  and  washed  clean. 

Art.  33.  The  sand  shall  be  dredged  from  the  Seine  and  well 
•cleansed  from  all  foreign  matter;  it  shall  be  screened  from  all 
grains  larger  than  f  inch  for  the  mortars  or  -f$  inch  for  grit  for 
the  mastic  pavements.  The  grit  for  this  last  purpose  shall  be 
perfectly  washed  and  dried  before  use. 

Art.  34.  The  mortar  of  hydraulic  lime  shall  be  composed  of  5 
parts  of  sand  and  2  parts  of  lime,  by  volume,  furnished  in  powder; 
the  mixture  shall  be  directly  reduced  to  a  paste  by  adding  the 
quantity  of  water  exactly  required  to  reduce  it  to  the  consistency 
of  plastic  clay. 

The  cement-mortar  shall  be  composed  of  1  part  of  hydraulic 
cement  of  Bourgogne  or  Portland  cement  of  Boulogne  and  3  parts 
of  sand;  the  sand  and  cement  shall  be  thoroughly  mixed  before 
the  addition  of  any  water.  All  mortar  which  shall  have  set  shall 
IDC  rejected. 

Art.  35.  The  beton  shall  be  composed  ordinarily  of  2  parts  in 
volume  of  mortar  and  3  of  stone.  The  mixture,  made  either  by 
rake  or  cylinder,  must  be  perfectly  uniform. 

All  beton  not  used  at  the  time  of  making  shall  be  rejected. 

Art.  36.  The  bed  of  beton  for  the  foundation  of  the  sidewalks 
shall  be  well  rammed  and  compressed,  and  must  at  least  commence 
to  set  and  dry  before  receiving  mastic  or  asphalt.  The  beton 
shall  in  addition  be  covered  with  a  layer  of  mortar  f  inch  thick. 

The  gravel  for  foundation  shall  pass  in  every  direction  through 
a  ring  2  inches  in  diameter.  It  must  be  perfectly  compressed  and 
sprinkled  with  lime-grout.  This  foundation  shall  have  commenced 


536  HIGHWAY    CONSTRUCTION.       ' 

to  set  before  the  application  of  the  mastic,  and  shall  be  covered 
with  a  layer  of  mortar  like  the  beton. 

Art.  39.  The  ground  upon  which  the  mastic  pavement  is  to  be 
placed  shall  always  be  previously  rammed,  watered,  and  crowned 
with  care.  When  it  is  thus  made  solid  the  contractor  shall  spread 
over'it  the  foundation  layer,  formed  according  to  the  orders  of  the 
engineer — either  a  bed  of  beton  or  of  sand  covered  by  a  layer  of 
mortar,  or  a  bed  of  sand  impregnated  with  goudron  2f  inches  thick, 
or  any  other  foundation  prescribed  by  the  engineer. 

In  all  cases  the  pavement  shall  not  be  laid  till  the  foundation 
has  attained  the  firmness  desired  and  becomes  quite  dry. 

The  contractor  must  conform  to  the  following  orders  for  the 
manufacture  of  the  mastic  to  be  used  for  pavements : 

The  mastic  shall  be  prepared  and  cast  in  one  or  more  manufac- 
tories belonging  to  the  contractor,  and  which  shall  always  remain 
open  to  the  inspection  of  the  engineers  and  their  agents. 

The  contractor  shall  besides  establish  in  the  manufacturing 
depots,  both  of  asphalt  and  mastic,  offices  exclusively  for  the 
agents  of  the  administration  set  apart  for  the  inspection  of  the 
composition  of  these  materials.  These  materials  shall  not  be 
admitted  into  the  works  without  a  carter's  delivery  note  given  by 
the  inspector,  setting  forth  that  they  have  been  manufactured  in 
accordance  with  the  specifications. 

There  shall  only  be  allowed  in  the  works  blocks  of  mastic  con- 
forming to  the  samples  deposited  and  accepted  before  the  award, 
and  bearing  the  trade-mark,  or  the  old  mastics  from  the  walks 
and  streets  of  Paris.  All  other  bituminous  matters,  resinous  or 
fatty,  found  in  the  works  by  the  agents  of  the  administration  will 
subject  the  contractor  to  a  deduction  of  $100  for  each  time  they  are 
found. 

To  assure  the  execution  of  these  conditions  the  contractor  must 
not  have  in  any  manufactory,  under  the  same  penalty,  any  other 
blocks  than  those  which  should  be  prepared  in  his  works,  and  the 
old  mastics  that  have  been  taken  up. 

The  use  of  the  old  mastic  is  authorized  in  the  works  of  the  city 
in  the  proportion  of  one  half  with  the  new;  the  pieces  of  the  old. 
sidewalks  having  been  perfectly  cleaned  with  great  care,  and  re- 
generated by  the  addition  of  new  purified  bitumen  and  a  sufficient 


FOOTPATHS,  CURBS,   GUTTERS.  537 

quantity  of  powered  asphalt  to  render  the  old  mastic,  when  melted, 
of  the  aspect  and  consistence  of  the  blocks  in  fusion. 

This  mastic  shall  be  melted  in  hermetically  closed  boilers,  on 
wheels  of  a  model  approved  by  the  administration,  and  arranged  so 
that  the  material  can  be  conveyed  from  the  factory  to  the  place  to 
be  used,  ready  to  be  employed. 

For  melting,  the  mastic  is  broken  into  pieces  4  inches  cube, 
then  the  bitumen  is  melted  and  the  mastic  added  little  by  little. 

The  grit  must  not  be  thrown  into  the  boiler  till  the  mastic  is 
completely  dissolved. 

During  the  whole  time  of  the  operation  the  matter  must  be 
stirred  up  almost  constantly,  so  that  the  combination  shall  be  well 
made  and  the  mastic  not  burned. 

The  mastic  being  well  melted  and  perfectly  homogeneous,  it 
shall  be  run  out  in  bands  of  about  five  feet  wide,  spread  with  a 
wooden  float,  and  levelled  with  a  strike,  so  as  to  present  neither 
fissure  nor  joint.  The  mastic  must  be  perfectly  level,  and  matched 
exactly  with  the  curbs,  etc.,  against  which  it  is  laid.  For  this  pur- 
pose the  parts  of  the  curbs,  flags,  etc.,  which  will  be  in  contact  with 
the  bitumen  shall  be  previously  warmed  and  goudroned. 

Art.  40.  Upon  the  soil,  well  shaped  and  rammed,  shall  be 
placed  a  bed  of  concrete,  covered  with  a  layer  of  mortar. 

The  asphaltic  rock,  conforming  to  article  24,  broken  down  or  de- 
crepitated by  heat,  shall  be  raised  to  a  uniform  temperature  of  from 
248  to  266  degrees  Fahr.,  and  carried  to  the  place  of  employment  in 
vehicles  that  will  prevent  as  much  as  possible  the  loss  of  heat.  It 
must  be  completely  freed  from  the  the  water  it  contains.  The  use 
of  old  compressed  asphalt,  taken  from  old  roads,  is  authorized  for 
mixture  with  new  asphalt,  in  the  proportion  of  one  quarter  of  old  com- 
pressed to  three  quarters  of  new  rock,  provided  that  the  old  shall  be 
cleansed  with  great  care  before  grinding  and  mixing  with  the  new. 

Asphalt  shall  not  be  put  on  the  concrete  foundation  until  it  is 
perfectly  set  and  dry. 

The  powder  shall  be  spread  with  a  thickness  about  two  fifths 
more  than  the  finished  thickness,  levelled  with  great  care,  and  then 
rammed,  at  first  carefully,  then  gradually  augmenting  the  force  by 
means  of  cast-iron  pilous  heated  to  the  proper  temperature  in 
portable  furnaces.  In  specially  exceptional  cases  the  compression 


538  HIGHWAY   CONSTRUCTION. 

may  also,  with  the  written  permission  of  the  engineer,  be  accom- 
plished by  means  of  rollers. 

In  every  case,  after  the  pilonnage  is  finished,  the  surface  shall 
be  smoothed  by  means  of  a  heated  iron  (lissoir). 

The  road  shall  not  be  open  to  traffic  until  it  is  quite  cool. 

Art.  43.  In  conformity  with  the  contract  price,  stipulated  here- 
after, diminished  by  the  rebate  of  the  awarded  contract,  the  con- 
tractor must  make  the  necessary  repairs  to  all  asphaltic  mastic  foot- 
paths and  areas,  furnishing  the  necessary  labor  and  materials,  so  that 
they  shall  be  kept  in  proper  condition.  He  must  each  year  of  the 
duration  of  the  contract  completely  relay,  in  new  material,  at  least 
the  fifteenth  part  of  the  surfaces  of  mastic  and  compressed  asphalt. 
The  surfaces  in  mastic  must  be  properly  plane  and  regular,  pre- 
senting neither  hollows  nor  projections  of  more  than  f  inch  in  a 
circle  whose  radius  is  3J-  feet.  These  surfaces  must  be  free  from 
fissures. 

Art.  45.  As  the  works  in  asphalt  or  mastic  are  accepted  by  the 
engineer  they  will  pass  into  the  charge  of  the  contractor,  who  will 
receive  for  the  maintenance  the  price  stipulated,  commencing 
from  the  first  of  January  next  following  their  acceptance,  what- 
ever may  be  the  date  of  said  acceptance. 

In  the  last  nine  months  of  the  year  instalments  may  be  paid  on 
the  contract  when  the  engineers  recognize  that  the  conditions  have 
been  loyally  carried  out.  The  accumulated  sums  of  these  instal- 
ments must  not  exceed  four  fifths  of  the  amount  of  the  sums  which 
shall  be  due  after  the  time  has  expired.  The  balance  of  the  con- 
tract price  of  the  year  will  be  paid  in  the  course  of  the  first  quarter 
of  the  following  year. 

Art.  49.  All  damages  in  the  bituminous  surface,  such  as  fissures 
or  cracks  of  at  least  y1^  inch  in  width,  or  parting  from  the  curbs  T3^ 
inch  in  width,  any  lifting  up  or  breaking  away  of  the  mastic  for  at 
least  ^  inch  in  depth,  depressions  in  consequence  of  settlement  of 
at  least  f  inch  in  depth  under  a  straight-edge,  3J  feet  long,  will 
subject  the  contractor  to  a  deduction  of  3  francs  (58  cents)  per  day 
when  the  repairs  shall  not  have  been  done  within  48  hours  after 
notice  given  by  the  engineer. 

Art.  51.  During  the  continuance  of  irost,  and  during  the  first 
month  after  the  commencement  ol  the  thaw,  there  shall  be  no  re- 
pairs to  the  pavements  maintained  by  the  contractor,  and  the  in- 


FOOTPATHS,  CURBS,  GTTTTEKS.  539 

spection  for  defects  shall  be  suspended ;  but  the  contractor  shall  fill 
with  sand  and  gravel  any  holes  in  these  pavements  within  24  hours 
&fter  notification  by  the  engineer,  under  a  penalty  of  10  francs 
-($1.93)  for  each  day  they  remain  unfilled.  He  may  be  authorized, 
in  exceptional  cases,  to  fill  the  holes  with  broken  flint  or  melted 
bitumen,  but  must  replace  the  flint  or  bitumen  with  asphalt  as  soon 
as  the  weather  permits.  It  must  be  so  arranged  that  the  main  re- 
pairs, intended  to  re-establish  the  normal  outline  of  the  roadways, 
:are  effected  from  May  1st  to  November  1st. 

Art.  65.  When  a  workman  leaves  one  of  the  districts  of  the 
works  under  the  municipal  service,  he  must  have  a  certificate  from 
the  contractor  showing  the  cause  for  which  he  left. 

This  certificate  shall  be  submitted  at  once  to  the  engineer,  who 
.shall  be  at  liberty  to  refuse  the  right  of  employing  the  said  work- 
man, without  the  contractor  deriving  therefrom  any  excuse  for 
not  furnishing,  when  requisite,  the  number  of  workmen  required. 
Jn  default  of  a  certificate,  the  workman  cannot  be  admitted,  except 
on  the  written  order  of  the  engineer. 

782.  Compressed-asphalt  Tile-pavement. — The  success  attend- 
ing the  introduction  of  compressed-asphalt  blocks  for  light-traffic 
streets  has  led  to  the  use  of  the  same  composition  under  the  name 
of  "  compressed-asphalt  tiles  "  for  sidewalk  pavements.  These 
tiles  can  be  made  of  any  form  and  thickness  required.  The  dimen- 
sions found  most  suitable  are  8  x  8  inches  square  and  2  J  inches  thick. 
In  this  form  they  have  been  laid  in  large  quantities  during  the  last 
seven  years  and  appear  to  have  given  satisfaction. 

782a.  Specifications  for  Laying-  Compressed-asphalt-tile  Side- 
walk-pavements. 

(1)  The  tiles  will  be  laid  on  a  foundation  of  gravel  and  sand 
thoroughly  compacted  by  ramming  and  rolling. 

(2)  The  space  over  which  the  pavement  is  to  be  laid  shall  be  ex- 
cavated to  the  depth  of  ten  (10)  inches  below  the  top  surface  of  the 
finished  pavement.     Any  perishable  or  other  objectionable  material 
found  below  this  depth  must  be  removed  and  the  space  filled  with 
•clean  gravel  or  sand ;  the  surface  of  the  foundation  so  prepared  shall 
be  thoroughly  compacted  by  ramming  and  rolling. 

(3)  The  foundation  for  the  tiles  will  be  formed  of  a  bed  of  fine 
bank  gravel  four  inches  in  depth  when  compacted,  screened  from 
all  pebbles  measuring  more  than  one  and  one-half  inches.     Upon 


540  HIGHWAY    CONSTRUCTION. 

the  gravel  there  shall  be  laid  a  bed  of  fine,  sharp  sand,  washed  and 
dried,  four  inches  in  thickness.  The  foundation  of  sand  and  gravel 
shall  then  be  thoroughly  consolidated  by  ramming  and  rolling,  care 
being  taken  to  preserve  the  surface  of  the  sand  parallel  to  the  slope 
required  for  the  finished  surface  of  the  pavement.  (The  hand- 
rammers  shall  weigh  not  less  than  25  Ibs.,  and  the  rollers  not  less- 
than  300  Ibs.) 

(4)  The  tiles  shall  be  laid  at  right  angles  to  the  street  line,  and 
their  surface  when  finished  must  be  even  with  the  top  of  the  curb 
and  shall  have  the  required  slope. 

The  tiles  shall  be  laid  by  the  pavers  standing  or  kneeling  upon 
the  tiles  already  laid,  and  not  upon  the  sand-bed. 

Each  course  of  tiles  must  be  of  uniform  width  and  depth,  and 
so  laid  that  all  longitudinal  joints  shall  be  broken  by  a  lap  of  at 
least  two  inches. 

Each  course  shall  be  driven  against  the  course  preceding  it  by 
a  maul  so  as  to  make  tight  joints. 

When  thus  laid  the  tiles  will  be  covered  with  clean,  fine,  dry 
sand,  free  from  loam  or  earthy  matter,  and  screened  through  & 
sieve  having  not  less  than  20  meshes  to  the  inch. 

(5)  The  tiles  shall  then  be  carefully  rammed  by  placing  a  plank 
over  several  courses  and  striking  the  plank  with  a  rammer  weigh- 
ing not  less  than  25  Ibs. 

The  ramming  shall  be  continued  until  the  tiles  reach  a  firm,  un- 
yielding bed  and  present  a  uniform  surface  with  the  required 
grade.  Any  lack  of  uniformity  in  the  surface  must  be  corrected  by 
taking  up  the  tiles  and  relaying  them. 

When  the  ramming  is  completed  a  thin  layer  of  fine  dry  sand 
shall  be  spread  over  the  surface  and  swept  into  the  joints. 

784.  Brick.— Brick  of  suitable  quality  well  and  carefully  laid 
on  a  concrete  foundation  makes  an  excellent  footway  pavement 
for  residential  and  suburban  streets  of  large  cities,  and  also  for  the 
main  streets  of  the  smaller  towns.  The  bricks  should  be  a  good 
quality  of  paving-brick  (ordinary  building-brick  are  unsuitable: 
they  soon  wear  out  and  are  easily  broken).  The  bricks  should  be 
laid  in  parallel  rows  on  their  edges,  with  their  length  at  right 
angles  to  the  axis  of  the  path.  They  should  be  set  in  cement- 
mortar  and  the  joints  filled  flush  and  made  as  close  as  possible. 


FOOTPATHS,  CURBS,  GUTTERS.  541 

785.  Specifications  for  Brick  Walks  (Washington,  D.  C.).— 
Brick  pavements  will  be  laid  on  a  foundation  of  gravel  and  sand; 
and  the  bricks  will  be  furnished  by  the  District,  delivered  on  the 
line  of  the  work.  The  space  over  which  the  pavement  is  to  be 
laid  will  be  excavated  to  the  depth  of  10  inches  below  the  top 
surface  of  the  proposed  pavement  when  thoroughly  compacted  by 
rolling  or  ramming.  Any  objectionable  or  unsuitable  material 
below  the  bed  will  be  removed,  and  the  space  filled  with  clean 
gravel  or  sand.  Care  must  be  taken  in  excavating  to  preserve  the 
proper  slope  parallel  with  the  surface.  Upon  the  foundation  will 
be  laid  a  bed  of  fine  sandy  bank  gravel,  4  inches  in  depth  when 
compacted,  screened  from  all  pebbles  measuring  more  than  1J 
inches  in  their  largest  dimensions,  and  thoroughly  rolled  or 
rammed.  Upon  this  will  be  laid  a  bed  of  fine,  clean,  sharp  sand, 
4  inches  in  thickness,  to  serve  as  a  bed  for  the  bricks,  which  will 
be  laid  directly  upon  and  imbedded  in  it  with  close  joints.  Special 
care  will  be  observed  to  make  the  surface  of  this  bed  of  sand 
parallel  to  the  surface  of  the  pavement  when  finished.  The  bricks 
must  be  laid  by  the  pavers  standing  or  kneeling  upon  the  bricks 
already  laid,  and  not  upon  the  bed  of  sand. 

The  bricks  are  to  be  laid  at  right  angles  with  the  line  of  the 
street,  or  in  herring-bone  style,  as  may  be  directed  by  the  Engineer 
Commissioner,  and  even  with  the  top  of  the  curb  when  rammed; 
each  course  to  be  of  bricks  of  a  uniform  width  and  depth,  and  so 
laid  that  all  longitudinal  joints  shall  be  broken  by  a  lap  of  at  least 
2  inches.  When  thus  laid  the  bricks  will  be  immediately  covered 
with  clean,  fine,  dry  sand,  free  from  loam  or  earthy  matter,  and 
screened  through  a  sieve  or  screen  having  not  less  than  20  meshes 
to  the  inch.  The  bricks  will  then  be  carefully  rammed  by  placing 
a  plank  over  several  courses  and  ramming  the  plank  with  a  heavy 
hammer.  The  ramming  will  be  continued  until  the  bricks  reach  a 
firm,  unyielding  bed  and  present  a  uniform  surface,  with  proper 
grade  and  slope.  Any  lack  of  uniformity  in  the  surface  must  be  cor- 
rected by  taking  up  and  relaying.  When  the  ramming  is  complete 
a  sufficient  amount  of  fine,  dry  sand,  as  above  described,  will  be 
spread  over  the  surface  and  swept  or  raked  into  the  joints. 

Rectangular  spaces,  7  by  3  feet  in  dimensions,  will  be  left 
iinpaved  around  trees  where  already  planted,  and  at  intervals  of 
25  feet  between  centres  adjacent  to  the  curb  on  streets  where 


542  HIGHWAY    CONSTRUCTION. 

trees  have  not  been  planted.  When  so  ordered  a  continuous  tree 
space  of  4  feet  wide  will  be  left  unpaved  adjacent  to  the  curb. 
Edges  of  brick  pavements  when  not  abutting  against  the  curb 
will  be  finished  with  a  continuous  row  of  brick  on  edge. 

Quality  of  Brick. — Sidewalk  paving-brick  to  be  of  dimensions 
8J  by  4  by  2£  inches,  hard-burned  throughout,  of  dark  red  color> 
without  flaws  or  cracks,  and  square  and  true  on  the  edges.. 
Specimens  required. 

Arch-bricks  to  be  of  dimensions  8J  by  4,  by  2J  inches,  hard- 
burned  throughout,  sound,  and  of  true  and  regular  shape.  All  to 
conform  to  the  samples  submitted  with  the  proposals.  No  swelled 
brick  or  soft  or  salmon  brick  will  be  allowed.  Specimens  required. 

In  relaying  brick  sidewalks  the  existing  sidewalks  will  be  taken, 
up  and  the  bricks  carefully  piled  and  preserved.  The  bed  will  then 
be  prepared  in  the  same  manner  as  prescribed  for  new  brick  walks. 
After  the  bed  is  prepared  the  old  brick  will  be  cleaned  of  all  adher- 
ing materials  so  that  they  can  be  relaid  with  close  joints,  when  they 
will  be  laid  as  prescribed  for  new  brick  pavements. 

786.  Artificial  Stone. — Artificial  stone  is  being  extensively  used 
as  a  footway-paving  material  both  in  Europe  and  America.     Its. 
manufacture  is  the  subject  of  several  patents,  and  numerous  kinds 
are  to  be  had  in  the  market.     When  manufactured  of  first-class, 
materials  and  laid  in  a  substantial  manner,  with  proper  provision 
against  the  action  of  frost,  artificial  stone  forms  a  durable,  agreeable, 
and  inexpensive  pavement. 

The  varieties  most  extensively  used  in  the  United  States  are 
known  by  the  names  of  "  granolithic,"  "  monolithic,"  "  f errolithic," 
"  kosrnocrete,"  "  metalithic,"  etc. 

The  process  of  manufacture  is  practically  the  same  for  all  kinds,, 
the  difference  being  in  the  materials  employed;  the  usual  ingredi- 
ents are  Portland  cement,  sand,  gravel,  and  crushed  stone. 

787.  Artificial  stone  for  footway  pavements  is  formed  in  two- 
ways,  viz.,  in  blocks  manufactured  at  a  factory  and  brought  on  the 
ground  and  laid  in  the  same  manner  as  natural  stone,  or  the  raw 
materials  are  brought  upon  the  work,  prepared  and  laid  in  place, 
blocks  being  formed  by  the  use  of  board  moulds. 

788.  The  manner  of  laying  is  practically  the  same  for  all  kinds. 
The  area  to  be  paved  is  excavated  to  a  minimum  depth  of  8  inches,, 
and  to  such  greater  depths  as  the  nature  of  the  ground  may  require 


FOOTPATHS,  CURBS,  GUTTERS.  543 

to  secure  a  solid  foundation.  The  surface  of  the  ground  so  exposed 
is  well  compacted  by  ramming,  and  a  layer  of  gravel,  ashes,  clinker, 
or  other  suitable  material  is  spread  and  consolidated;  on  this  is 
placed  the  concrete  wearing  surface,  usually  4  inches  thick.  As  a 
protection  against  the  lifting  effects  of  frost  the  concrete  is  laid  in 
squares,  rectangles,  or  other  forms  having  areas  ranging  from  6  to 
30  square  feet,  strips  of  wood  being  employed  to  form  moulds  in. 
which  the  concrete  is  placed.  After  the  concrete  is  set  these 
strips  are  removed,  leaving  joints  about  half  an  inch  wide  between 
the  blocks.  Under  some  patents  these  joints  are  filled  with  cement, 
under  others  with  tarred  paper,  and  in  some  cases  they  are  left  open. 

789.  Good  artificial  stone  is  far  superior  to  any  other  material 
for  footway  pavements.     It  is  of  a  uniform  temper  and  homoge- 
neous throughout,  and  consequently  its  wear  is  more  uniform  than 
that  of  natural  stones.     It  is  practically  non-absorbent,  and  conse^ 
quently  dries  very  quickly  after  rain. 

790.  The  quality  of  the  cement  is  an  important  point  in  the 
manufacture  of  artificial  stone.    A  cement  of  improper  quality  will 
cause  cracking.     The  characteristics  of  good  cement  are  treated  of 
in  Chapter  IX. 

New  Portland  cement  when  spread  and  subjected  to  a  process  of 
aeration  will  increase  in  bulk  at  least  5  per  cent.  If  stones  are 
manufactured  with  such  cement  they  will  blow  and  crack.  Cement 
increases  in  strength  with  age,  and  therefore  stone  manufactured 
with  it  will  also  increase  in  the  same  ratio;  and  again,  Dykerhoff 
has  shown  that  slow-setting  cement  had  an  average  expansive  power 
of  .0734  per  cent,  and  quick-setting  .2019  per  cent,  over  a  period  of 
twelve  months. 

791.  The  following  detailed  particulars  for  the  laying  of  con- 
crete footway  pavements  is  taken  from  "  Eoads,  Streets,  and  Pave- 
ments," by  Q.  A.  Gillmore : 

"  Concrete  footpaths  should  be  laid  upon  a  form  of  well-com- 
pacted sand,  or  fine  gravel,  or  a  mixture  of  sand,  gravel,  and  loam 
The  natural  soil,  if  sufficiently  porous  to  provide  thorough  sub- 
drainage,  will  answer. 

"  It  is  not  usual  to  attempt  to  guard  entirely  against  the  lifting 
effects  of  frost,  but  to  provide  for  it  by  laying  the  concrete  in 
squares  or  rectangles,  each  containing  from  12  to  16  superficial 
feet,  which  will  yield  to  upheaval  individually  like  flagging  stones, 


544  HIGHWAY    CONSTRUCTION. 

without  breaking  and  without  producing  extensive  disturbance  in 
the  general  surface. 

"  When  a  case  arises,  however,  where  it  is  deemed  necessary  to 
prevent  any  movement  whatever,  it  can  be  done  by  underlaying  the 
pavement  with  a  bed  of  broken  stone,  or  a  mixture  of  broken  stone 
and  grave],  or  with  ordinary  pit-gravel  containing  just  enough  of 
detritus  and  loam  to  bind  it  together.  In  high  latitudes  this  bed 
should  be  1  foot  and  upwards  in  thickness,  and  should  be  so 
thoroughly  subdrained  that  it  will  always  be  free  from  standing 
water.  It  is  formed  in  the  usual  manner  of  making  broken-stone 
or  gravel  roads  already  described,  and  finished  off  on  top  with  a 
layer  of  sand  or  fine  gravel,  about  one  inch  in  depth,  for  the  con- 
crete to  rest  upon. 

"  The  concrete  should  not  be  less  than  3£  and  need  rarely  ex- 
ceed 4  to  4^  inches  in  thickness.  The  upper  surface  to  the  depth  of 
-£  inch  should  be  composed  of  hydraulic  cement  and  sand  only. 
Portland  cement  is  best  for  this  top  layer.  For  the  rest,  any 
natural  American  cement  of  standard  quality  will  answer.  The 
following  proportions  are  recommended  for  this  bottom  layer : 

Rosendale  or  other  American  cement 1     measure 

Clean,  sharp  sand 2£ 

Stone  and  gravel 5 

"  It  is  mixed  from  time  to  time  as  required  for  use,  and  is  com- 
pacted with  an  iron-shod  rammer  in  a  single  layer  to  a  thickness 
less  by  \  inch  than  that  of  the  required  pavement.  As  soon  as  this 
is  done  and  before  the  cement  has  had  time  to  set,  the  surface  is 
roughened  by  scratching,  and  the  top  layer,  composed  of  1  volume 
of  Portland  cement  and  2  to  2%  volumes  of  clean,  fine  sand,  is 
spread  over  it  to  a  uniform  thickness  of  about  1J  inches  and  then 
compacted  by  rather  light  blows  with  an  iron-shod  rammer.  By 
this  means  its  thickness  is  diminished  to  \  an  inch.  It  is  then 
smoothed  off  and  polished  with  a  mason's  trowel  and  covered  up 
with  hay,  grass,  or  other  suitable  material  to  protect  it  from  the 
rays  of  the  sun  and  prevent  its  drying  too  rapidly. 

"  It  should  be  kept  damp  and  thus  protected  for  at  least  ten 
days,  and  longer  if  circumstances  will  permit;  and  even  after  it  is 
open  for  travel  a  layer  of  damp  sand  should  be  kept  upon  it  for 
two  or  three  weeks,  to  prevent  wear  while  tender. 


FOOTPATHS,  CURBS,  GUTTERS.  545 

"  At  the  end  of  one  month  from  the  date  of  laying,  the  Port- 
land-cement mixture  forming  the  top  surface  will  hav<j  attained 
nearly  one  half  its  ultimate  strength  and  hardness,  and  may  then 
be  subjected  to  use  by  foot-passengers  without  injury. 

"  The  rammers  for  compacting  the  concrete  should  weigh  from  15 
to  20  pounds,  those  used  on  the  surface  layer  from  10  to  12  pounds. 
They  are  made  by  attaching  rectangular  blocks  of  hard  wood  shod 
with  iron  to  wood  handles  about  three  feet  long,  and  are  plied  in 
an  upright  position.  Certain  precautions  are  necessary  in  mixing 
and  ramming  the  materials  in  order  to.  secure  the  best  results. 
Especial  care  should  be  taken  to  avoid  the  use  of  too  much  water 
in  the  manipulation.  The  mass  of  concrete,  when  ready  for  use, 
•should  appear  quite  incoherent  and  not  wet  and  plastic,  contain- 
ing water,  however,  in  such  quantities  that  a  thorough  ramming 
with  repeated  though  not  hard  blows  will  produce  a  thin  film  of 
moisture  upon  the  surface  under  the  rammer,  without  causing  in 
the  mass  a  gelatinous  or  quicksand  motion." 

791a.  The  disintegration  and  disfiguration  of  cement  walks  is 
frequently  due  to  unskilful  manipulation.  While  the  surface  mix- 
ture should  be  thoroughly  rammed  and  well  trowelled,  yet  this  treat- 
ment should  not  be  continued  so  long  as  to  bring  to  the  surface  a 
considerable  quantity  of  neat  cement,  thus  leaving  the  layer  of 
mortar  next  below  without  sufficient  cement  to  bind  it  together. 
If  this  is  done,  the  thin  layer  of  cement  will  flake  off  when  set,  re- 
vealing a  layer  of  almost  clear  sand.  A  similar  result  obtains  if 
attempt  is  made  to  re  trowel  a  surface  once  finished  and  partially  set, 
but  afterwards  defaced.  Sprinkling  the  surface  before  the  cement 
has  thoroughly  set  may  cause  blisters,  which  mar  the  work.  If  the 
surface  of  the  setting  cement  is  not  protected  from  the  direct  rays 
•of  the  sun,  cracks  will  be  produced. 

792.  One  cubic  yard  of  concrete  laid  3  inches  thick  will  cover 
10  square  yards  of  surface.     For  the  wearing  surface  the  cement 
and  sand  are  mixed  in  equal  parts. 

793.  Covering  Capacity  of  Cement  in  Square  Feet. 

Thickness  in  Inches. 
1"  J"  *" 

1  bbl.  of  Portland  cement  *vill  cover 36        48         72 

1  bbl.  cement  and  1  bbl.  sand  will  cover 66        84        132 

1  bbl.  cement  and  2  bbls.  sand  will  cover 96      124        192 


546 


HIGHWAY    CONSTRUCTION". 


794.  Wear. — As  regards  the  wear  of  artificial  stones,  the  follow- 
ing notes  from  London  may  be  interesting:  "Artificial  stones  hav& 
now  been  used  by  almost  every  Vestry  and  District  Board  in  the- 
metropolis,  and  from  testimonials  it  would  appear  that  they  have- 
given  satisfaction." 

A  portion  of  Victoria  stone  was  laid  in  Piccadilly  in  1872,  and 
is  said  to  be  in  good  condition  still,  having  been  in  use  nineteen 
years. 

In  1869  the  approach  to  Blackfriars  Bridge  was  paved  with 
Victoria  stone>  and  six  years  later,  Mr.  Carr,  the  engineer,  said,  the 
surface  was  perfect  and  the  wear  decidedly  less  than  York  stone 
contiguous.  This  stone  has  also  been  laid  in  Holburn,  where  the 
traffic  is  estimated  at  88,355  persons  daily,  and  Aldgate  High  Street, 
where  the  traffic  is  estimated  at  79,048  daily.  Portions  of  the  stone 
were  taken  up  after  five  years,  and  the  wear  was  found  to  be  so 
slight  as  to  be  scarcely  measurable. 

Imperial  stone  has  also  been  largely  used  throughout  the 
metropolis,  and  appears  to  have  given  every  satisfaction. 

Several  varieties  of  good  stone  are  in  the  market;  as  examples 
the  following  may  be  cited: 


Cost  pet- 
yard  laid. 

Tensile  Strain 
in  pounds  per 
square  inch. 

Compressive 
Strain,  Jbs.  per 
square  inch. 

Thickness 
in 
inches. 

Weight  in. 
Ibs.  per 
cubic  ft. 

$1.35 
1.32 
1.38-1.44 
1.31 
1.30 

1.56 

980 

1,125 
1,000 
510* 
l,500f 

9,492 
9,394 
8,321 
8,500 

5,714 

1* 

2 
2 
8* 

3 

132 
144 

150 
156 

Croft  

Victoria 

Granolithic  

Jones  annealed.  .  .  . 
York  (natural)  

*  1  month  old. 


f  12  months  old. 


The  following  tests  were  made  by  Mr.  W.  Sykes,  Surveyor, 
Fulham,  London,  to  find  the  comparative  wear  of  artificial  and 
natural  stones.  The  stones  were  of  equal  superficial  area,  all  bound 
together  with  cord,  so  that  each  stone  found  its  own  bed  when, 
rubbed  on  York  stone  with  sand  and  water. 


FOOTPATHS,  CURBS,  GUTTERS. 


547 


York. 

Imperial. 

Victoria.    ' 

Croft. 

Thickness  before  being  rubbed.  . 
First  hour  

Si  in. 

2  » 

I1"' 

?tiD- 

*fn' 

I* 

a£ 

s 

2 

Third  hour                  .     ... 

2A 

2A 

2 

114 

Total  wear  

5 

£ 

•A 

A 

¥F 

¥? 

4F 

From  these  figures  it  will  be  seen  that  the  total  wear  in  the 
three  hours  was  for  York  J-J  of  an  inch,  Imperial  ¥3¥,  Victoria  ^, 
Croft  £y. 

This  experiment  is  interesting  as  showing  that  the  wear  of 
York  was  ^  inch  more  than  that  of  artificial  stone;  also  that  the 
Imperial,  Victoria,  and  Croft  wore-equally,  and  would  therefore  be 
of  the  same  degree  of  hardness. 

Th.e  York  stone  referred  to  above  is  a  sandstone  composed 
chiefly  of  silica  cemented  together  by  a  matrix  of  lime,  clay,  etc. ; 
it  is  of  very  unequal  quality,  being  either  exceedingly  hard  or  quite 
soft;  it  is  also  very  absorptive,  and  is  liable  to  laminate  under 
f  i  ost. 

795.  Specifications  for  Concrete  Footwalks. — Preparation  of 
Foundation. — The  natural-soil  surface  shall  be  regulated  and 
graded  to  a  depth  of  8  inches  below  the  level  of  the  finished  sur- 
face of  the  walk;  perishable  and  objectionable  material  shall  be  re- 
moved. On  the  surface  so  graded  spread  a  layer  of  clean  gravel 
(broken  bricks  or  steam  ashes)  to  such  depth  as  will  give  on 
thorough  consolidation  a  thickness  of  4  inches.  On  the  foundation 
so  prepared  the  concrete  shall  be  placed;  moulds  formed  of  ^-inch 
boards  shall  be  placed  at  every  6  feet  and  adjusted  to  the  required 
grade  and  pitch.  The  concrete  shall  be  placed  in  these  moulds  and 
thoroughly  rammed.  After  the  concrete  has  set,  its  surface  will  be 
covered  with  the  wearing  coat,  one  inch  thick,  the  surface  of  which 
shall  be  neatly  trowelled  to  the  required  grade. 

Traffic  shall  be  kept  off  for  a  period  of  15  days  or  until  the 
surface  is  thoroughly  set. 

All  vault-covers,  stop-cock  boxes,  etc.,  shall  be  adjusted  to  the 
required  grade,  and  the  concrete  shall  make  neat  and  close  connec- 
tion with  their  surface. 


548  HIGHWAY    CONSTRUCTION. 

The  concrete  shall  be  composed  of: 

American  hydraulic  cement 1  part 

Broken  stone 7  parts 

Gravel  and  sand 3     " 

The  wearing  surface  will  be  composed  of: 

Portland  cement ,    1  part 

Sharp  sand  1     " 

796.  Specifications  for  Artificial-stone  Footpaths  (Washington. 
D.  C.). — The  contractor  shall  remove  all  stone,  plank,  bricks,  or 
other  materials  of  value  from  points  where  the  sidewalk  is  to  be 
laid  as  the  work  progresses,  and  shall  haul  them  to  the  nearest 
property  yard,  or  otherwise  dispose  of  them  as  the  Engineer  Comis- 
sioner  may  direct.  Care  shall  be"  taken  at  all  times  not  to  interfere 
with  business  or  travel  more  than  is  absolutely  necessary  for  the 
faithful  performance  of  the  work.  No  more  than  100  feet  shall  be 
closed  to  travel  at  any  one  time,  nor  remain  closed  for  a  longer  time 
than  three  days,  and  free  ingress  and  egress  from  the  streets  to  all 
stores  and  hallways  shall  be  provided  for  at  all  times;  and  during 
the  time  that  travel  is  closed  at  any  point  the  contractor  shall  pro- 
vide a  temporary  walk,  said  walk  to  be  at  all  times  in  condition, 
perfectly  safe  for  pedestrians,  and  easy  of  access  from  adjoining 
walks. 

The  contractor  shall  make  such  cutting  and  filling  as  may  be 
necessary  to  bring  the  foundation  to  the  subgrade,  6  inches  below 
the  established  grade  of  the  sidewalk. 

Whenever  the  Engineer  Commissioner  or  inspector  may  deem 
it  necessary,  the  foundation  shall  be  consolidated  by  wetting,  rolling, 
or  ramming,  to  give  it  proper  stability.  Upon  the  foundation  thus 
prepared  there  shall  first  be  laid  3  inches  of  concrete,  composed  of 
one  part  natural  hydraulic  cement,  two  and  one  half  parts  sand,  and 
five  parts  broken  stone,  which  shall  be  rammed  in  place  to  the  satis- 
faction of  the  Engineer  Commissioner.  On  this  concrete  bed  shall 
be  laid  three  quarters  of  an  inch  of  mortar,  composed  of  four 
measures  of  clean,  sharp  sand  and  one  of  Portland  cement,  which 
shall  be  put  in  dry  as  possible,  and  rammed  in  place  with  an  iron 
rammer  weighing  at  least  25  pounds.  Upon  the  foundation  thus 
prepared  shall  be  laid  square  blocks  or  tiles  2%  inches  thick,  measur- 
ing 18  inches  on  a  side.  They  shall  be  laid  so  as  to  present  a  true 


FOOTPATHS,  CURBS,  GUTTERS.  549 

surface  on  top  and  conform  to  the  exact  grade  of  the  sidewalk.  A 
thin  grouting  of  pure  Portland  cement  of  the  best  quality  shall  be 
spread  over  the  surface  and  carefully  swept  into  the  joints.  All 
superfluous  grouting  shall  be  cleaned  off,  and  the  walk  shall  be 
protected  with  plank  or  otherwise  until  the  cement  has  thoroughly 
set. 

Driveways  crossing  the  footpath  shall  be  laid  with  granite  or 
asphalt  blocks,  as  may  be  directed  by  the  Engineer  Commissioner. 
The  tiles  shall  be  2$  inches  thick.  The  lower  If  inches  to  be  com- 
posed of  one  part  Portland  cement  (equal  to  that  specified  in 
current  District  of  Columbia  specifications)  and  two  parts  of  clean, 
sharp  sand,  thoroughly  mixed,  using  as  small  a  quantity  of  water 
as  possible,  and  carefully  rammed  into  the  moulds.  The  upper 
one-half  inch  and  the  sides  for  one-half  inch  shall  be  composed 
of  one  part  Portland  cement,  of  same  quality  as  above,  and  one  part 
clean,  sharp  sand. 

The  surface  shall  be  finished  smooth  but  not  polished „  The 
tiles,  when  being  seasoned,  shall  be  kept  wet  for  the  first  five  days. 
No  tiles  shall  be  used  on  the  work  unless  guaranteed  by  the  con- 
tractor to  be  at  least  thirty  days  old.  Unless  otherwise  ordered,  the 
edge  of  the  sidewalk  shall  be  finished  with  plastering  of  Portland 
cement  and  sand  of  equal  parts.  The  blocks  will  be  laid  with  the 
edges  perpendicular  to  or  parallel  with  the  line  of  the  street,  as  may 
be  ordered  by  the  Engineer  Commissioner. 

Cement  Inspection. — No  cement  shall  be  used  on  this  work 
unless  approved  by  the  Engineer  Commissioner.  For  this  purpose 
he  shall  be  entitled  to  take  one-half  pound  from  each  package. 
The  decision  of  the  Engineer  Commissioner  shall  be  final  in  all 
cases,  and  no  cement  condemned  by  him  shall  be  used  on  the  work 
for  any  purpose  whatever.  All  cements  will  be  required  to  pass  the 
tests  specified  in  current  District  of  Columbia  specifications. 

All  surplus  material  and  refuse  shall  be  removed  by  the  con- 
tractor twenty-four  hours  after  the  completion  of  the  work;  and  in 
case  of  neglect  on  the  part  of  the  contractor  to  do  so  within  the  speci- 
fied time,  the  Engineer  Commissioner  shall  have  the  same  removed, 
and  the  expense  thereof  shall  be  charged  to  the  contractor  and 
deducted  from  his  estimates.  Whenever  any  private  driveway 
crosses  the  sidewalk,  the  plan  thereof  shall  be  modified  as  the 
Engineer  Commissioner  shall  direct. 


550  HIGHWAY    CONSTRUCTION. 

No  material  of  any  kind  shall  be  used  until  it  has  been  examined 
and  approved  by  the  Engineer  Commissioner,  who  shall  have  full 
power  to  condemn  the  work  or  material  not  in  accordance  with  the 
specifications,  and  to  require  the  contractor  to  remove  any  work  or 
material  so  condemned,  and  at  his  own  expense  to  replace  the  said 
work  or  material  to  the  satisfaction  of  the  Engineer  Commissioner. 
In  case  the  contractor  shall  neglect  or  refuse,  after  written  notice, 
to  remove  or  replace  said  rejected  work  or  material,  it  shall  be 
removed  and  replaced,  by  order  of  the  Engineer  Commissioner,  at 
the  contractor's  expense. 

The  work  is  to  be  commenced  and  carried  on  at  such  times  and 
places  and  in  such  manner  as  the  Engineer  Commissioner  shall 
direct. 

The  contractor  will  not  be  allowed  to  obstruct  private  drive- 
ways or  approaches  or  to  dig  up  or  occupy  the  street  by  material 
more  than  is  absolutely  necessary  for  the  prosecution  of  the  work, 
special  care  being  taken  to  inconvenience  the  public  as  little  as 
possible. 

When  the  construction  of  any  piece  of  work  is  begun  it  shall  be 
fully  completed  before  the  force  is  removed.  In  case  this  is  not 
done,  the  Engineer  Commissioner  shall  have  the  work  done,  and 
the  expense  thereof  shall  be  charged  to  the  contractor  and  deducted 
from  his  estimates. 

If  any  overseer  or  workman  employed,  by  the  contractor  shall  be 
declared  by  the  Engineer  Commissioner  to  be  unfaithful  or  incom- 
petent, or  shall  refuse  to  obey  the  instructions  of  the  inspector,  the 
contractor  shall  forthwith  dismiss  such  person  and  not  again  employ 
him  on  any  part  of  the  work.  The  contractor  will  be  held  respon- 
sible for  all  injury  done  to  the  work  in  any  way  until  it  is  accepted 
and  measured  by  the  engineer. 

Measurement  of  JF0r&.— All  artificial  stone-block  walks,  includ- 
ing stone  and  mortar  foundation,  will  be  paid  for  by  the  square 
yard  of  finished  surface,  in  accordance  with  the  schedule  in  printed 
form  of-  bid,  except  when  it  is  fitted  around  poles,  lamp-posts,  or 
scuttle-holes,  in  which  case  these  spaces  will  not  be  deducted.  Tree- 
spaces  will  not  be  deducted. 

Curb. --—Whenever  ordered  the  curb. will  be  reset.  Curb  will  be 
redressed  by  the  contractor  whenever  ordered,  for  which  actual  cost 
plus  15  per  cent  will  be  paid. 


FOOTPATHS,  CURBS,  GUTTERS.  551 

Tree-spaces. — Tree-spaces  shall  be  left  wherever  necessary. 
These  spaces  shall  be  outlined  by  boards  of  sound  Georgia  pine,  2 
inches  thick  and  9  inches  wide,  set  on  edge,  with  their  top  edge 
even  with  the  pavement  when  completed.  The  plank  forming  the 
rear  of  this  framework  and  which  is  parallel  with  the  curb  shall  be 
firmly  nailed  to  the  other  two  pieces,  and  shall  be  cut  in  such  manner 
that  it  will  bind  underneath  the  pavement  when  completed.  The 
blocks  shall  be  laid  as  closely  to  the  boards  as  possible,  and  all  corners 
and  vacant  spaces  shall  be  filled  with  mortar  similar  in  composition 
to  that  of  which  the  blocks  are  made. 

796a.  Kosmocrete. — The  artificial  stone  known  by  this  name 
is  extensively  used  in  Brooklyn,  N.  Y.;  it  is  formed  as  follows  : 
A  bottom  course  of  dry  cinders,  about  12  inches  thick,  is  laid, 
and  upon  this  a  layer  of  concrete  about  4  inches  thick,  composed 
of  3  parts  of  granulated  granite  or  gravel,  4  parts  of  one  and 
one-half  inch  stone,  and  1  part  of  Portland  cement.  On  this  con- 
crete is  worked  a  facing  about  one  inch  thick,  composed  of  granu- 
lated granite,  a  small  percentage  of  silicious  grit,  Portland  cement, 
and  carbon.  The  purpose  of  the  granite  and  grit  is  to  prevent  the 
surface  from  becoming  slippery.  Cost  ranges  from  25  to  35  cents 
per  square  foot,  depending  largely  upon  the  distance  the  material 
has  to  be  transported,  and  the  amount  of  work  that  Las  to  be  done 
preliminary  to  laying  the  pavement. 

797.  Tar  Concrete  for  Footway  Pavements  is  made  in  many 
and  various  ways.  Pavements  made  according  to  the  following 
.specifications  have  proved  satisfactory: 

Proportions  of  materials : 

Steam  aslies ; 3  parts 

Portland  cement .1  part 

Sharp  sand , 1     " 

Gas-tar 9  parts 

'  Water 70  to  80     " 

Method  of  Mixing. — The  ashes,  sand,  and  cement  are  thoroughly 
mixed  dry,  then  the  water  and  tar  added  and  mixed  in  the  same 
manner  as  mortar.  The  plastic  mass  thus  produced  is  passed  several 
times  through  a  pug  mill :  if  this  is  not  done,  the  concrete  will  be  a 
failure.  As  the  mass  emerges  from  the  mill  a  large  proportion  of 
the  water  will  run  from  it,  and  means  must  be  provided  to  allow  it 
to  escape  freely. 


552  HIGHWAY    CONSTRUCTION. 

The  foundation  is  prepared  in  the  usual  manner  and  the  concrete 
laid  3  to  4  inches  in  thickness,  well  rammed  with  hand  rammers* 
then  rolled  with  an  iron  roller  weighing  not  less  than  600  pounds — 
the  amount  of  rolling  to  be  not  less  than  two  hours  for  each  100 
square  feet.  Hollows  that  appear  during  the  rolling  to  be  trimmed 
and  filled  up.  After  the  concrete  is  set  sprinkle  a  small  quantity 
of  clean,  sharp  sand  over  the  surface  and  allow  it  to  remain  for  three 
or  four  days  after  the  path  has  been  in  use,  then  remove  it. 

The  concrete  should  not  be  laid  in  wet  or  freezing  weather. 

798.  Another  method  of  forming  tar-concrete  pavements  is  as 
follows :     On  a  dry  foundation  is  placed  a  coat  of  rough  clinkers, 
from  anthracite  coal,  or  iron  clinkers  from  a  foundry,  mixed  with 
sand  and  tar  in  the  proportions  of  15  cubic  feet  of  fine  sifted  ashes,. 
14^  cubic  feet  of  pit  sand,  and  li  cubic  feet  or  9  gallons  of  tar.    This 
is  laid  about  3  or  4  inches  thick  and  well  rolled.    Over  this  is  placed 
a  coating  from  1  inch  to  1^  inches  thick,  composed  of  15  cubic  feet 
of  coarse  sifted  ashes,  15  cubic  feet  of  clinkers,  and  1|  cubic  feet  or 
8  gallons  of  tar.     It  must  then  be  well  rolled  and  sanded,  care  hav- 
ing been  taken  that  the  materials  are  thoroughly  mixed. 

799.  Footway  pavements  of  which  the  binding  material  is  coal- 
tar  must  only  be  reckoned  as  temporary.    They  have  been  extensively 
used  in  several  cities,  but  as  a  rule  they  soon  wear  out  and  become 
very  disagreeable.     Under  a  hot  summer  sun  the  pavement  becomes 
soft  and  sticky,  the  volatile  oils  are  evaporated,  and  the  surface  be- 
comes covered  with  ridges ;  they  are  difficult  to  repair  and  are  never 
satisfactory. 

800.  Gravel. — For  suburban  streets,  country  roads,  parks,  and 
pleasure-grounds,  gravel  makes  an  excellent  footway  pavement. 

The  same  rules  that  apply  to  the  construction  of  gravel  road- 
ways apply  to  gravel  footways.  They  must  be  well  drained  and 
well  rolled. 

Limestone  chippings  may  with  advantage  be  used  with  pit 
gravel.  For  paths  formed  of  gravel  a  crowning  surface  looks  better 
and  is  more  enduring  than  a  sloping  one.  (See  Fig.  149.) 

801.  As  examples  of  excellent  rural-walk  construction,  the  walks 
of  Central  Park,  N.  Y.,  may  be  cited.  These  walks  embrace,  in 
treatment  and  materials,  the  requirements  of  the  generality  of  rural 
walks  in  this  country.  They  are  laid  on  every  variety  of  ground,, 
from  level  and  smooth  to  rocky  and  precipitous,  sometimes  clamber- 


FOOTPATHS,  CURBS,  GUTTERS.  553 

ing  with  rustic  steps  and  winding  narrowly  along  rugged  hillsides ; 
sometimes  gently  undulating  over  meadows  and  lawns,  and  some- 
times expanding  into  broad  and  capacious  promenades.  They  are 
carried  over  and  under  roads,  and  over  brooks,  by  archways  and 
bridges  of  various  kinds,  ornamental  and  rustic;  through  gorges 
and  ravines,  and  along  the  water  edge  of  lakes  and  ponds.  They 
are  made  of  various  widths,  from  3J  to  35  feet,  and  adapted  to 
nearly  every  circumstance  of  position,  locality,  use,  and  convenience 
that  ordinarily  occurs  in  walks  for  rural  or  park  purposes. 

802.  The  general  method  of  constructing  the  walks  was  as  fol- 
lows :  In  the  more  formal  walks — those  having  the  greatest  breadth 
and  occupying  ground  that  was  originally  so  irregular  and  uneven 
as  to  require  a  considerable  amount  of  excavating  and  filling — the 
preparation  of  the  bed  of  the  walk  was  the  same  as  for  the  roads. 
Care  was  taken  to  compact  the  earth  in  the  embankments,  exclud- 
ing all  perishable  and  improper  materials. 

The  bed  of  the  walk  was  raised  in  the  centre,  with  a  moderate 
inclination  toward  the  sides,  and  where  not  sufficiently  firm  was. 
rolled  with  a  hand-  or  horse-roller.  The  sub-drainage  was  se- 
cured by  drains  formed  sometimes  of  tiles  and  sometimes  of 
rubble-stone,  so  placed  as  to  intercept  and  carry  off  the  water  from 
rain  and  springs.  "  Mitre  drains  "  formed  of  small  stones  were  em- 
ployed where  necessary. 

803.  One  of  the  principal  causes  of  the  deterioration  of  walks, 
and  a  prolific  source  of  trouble  and  expense  in  repairs,  is  the  wash 
from  water  brought  from  the  adjoining  slopes.     If  the  expense  of 
making  good  the  damage  done  in  this  way — sometimes  by  a  single 
shower — is  considered,  it  will  be  seen  that  a  liberal  and  ample  pro- 
vision to  guard  against  it  is  warranted  by  sound  economy.     No 
cheaper  or  more  effective  and  practical  method  can  be  adopted  for 
this  object  than  the  catch-water  drains,  or,  as  they  have  been  termed 
in  the  Park,  "  sod  gutters/' 

These  are  made  along  the  uphill  side  of  the  walk,  in  the  form  of 
a  broad  grave,  parallel  for  the  most  part  with  the  walk  and  a  few 
feet  from  it,  and  joined  by  an  easy  graduation  of  surface  to  the 
ground  on  each  side,  so  as  to  give  them  as  little  of  an  artificial 
appearance  as  practicable.  The  bottom  is  made  even  and  regular, 
with  no  depressions  to  lodge  silt  or  mud,  or  form  pools  of  water. 
When  properly  shaped  the  surface  is  sodded  and  rammed. 

After  the  grass  has  taken  root,  the  gutter  will  bear  the  passage 


554 


HIGHWAY    CONSTRUCTION. 


of  a  considerable  volume  of  water  for  as  long  a  time  as  is  ordinarily 
required,  without  receiving  injury.  This  form  of  gutter  admits  of 
the  mowing  of  the  grass  that  grows  in  it  without  difficulty,  which 
is  a  great  convenience.  If  the  walk  passes  through  a  hollow,  with 
descending  ground  from  each  way,  these  gutters  are  made  on  each 
side  of  the  walk.  When  it  occupies  ground  that  is  level  transversely, 
it  is  raised  slightly  above  the  surface,  to  give  an  outward  inclina- 
tion to  the  turf  borders  and  turn  the  water  away  from  it. 

The  gutters  are  conducted  along  the  walk,  parallel  with  it,  or 
deviating  occasionally  to  take  advantage  of  convenient  natural 
depressions,  until  a  favorable  point  is  reached  for  turning  off  the 
water  altogether,  and  disposing  of  it  in  a  secure  manner.  Where  it 
is  practicable,  the  water  is  allowed  to  spread  out  from  the  termina- 
tion of  a  gutter  upon  a  broad  surface  of  descending  ground,  and 
seek  the  general  drainage  courses  of  the  district  in  which  it  is  situ- 
ated, that  lead  to  a  sewer  inlet,  a  brook,  or  a  pond.  Sometimes  the 
gutter  is  conducted  to  a  sewer  or  road  drain  in  the  vicinity;  but 
when  facilities  of  this  kind  are  not  available,  and  it  is  objectionable 
or  unsafe  to  discharge  an  accumulation  of  water  upon  a  lawn  or 
through  shrubbery,  special  under-drains  have  had  to  be  constructed. 
Such  under-drains  have  been  necessary,  to  a  considerable  extent,  in 
connection  with  most  of  the  main  walks  of  the  Park.  They  receive 
through  grated  inlets,  inserted  in  the  gutters  (with  accompanying 
silt-basins),  the  immediate  drainage  of  the  walks,  and,  through 
similar  inlets  placed  in  the  adjoining  sod  gutters,  the  exterior 
drainage.  Fig.  161  shows  the  arrangement  of  these  drains,  inlets, 

m 


FIG.  161.    SECTION  OF  PARK  WALK,  SHOWING  THE 
MANNER  OF  REMOVING  THE  SURFACE  WATER. 

and  silt- basins.     The  depression  on  the  right  of  the  figure  shows  in 
section  a  sod  gutter  (or  a  natural  surface  channel),  having  an  inlet 


FOOTPATHS,  CURBS,  GUTTERS.  555 

to  the  main  and  under  drain  through  a  silt-basin,  which  is  repre- 
sented under  the  right  walk  gutter.  The  inlets  and  silt-basins 
occur  in  this  manner  at  intervals  of  one  hundred  to  three  hundred 
i'eet,  according  to  circumstances,  the  amount  of  drainage,  the  de- 
clivity of  the  walks,  etc.  The  under-drain  is  carried  various  dis- 
tances along  the  walk,  until  it  becomes  convenient  to  turn  it  into  a 
larger  road-drain  or  a  sewer. 

Where  the  under-drains  and  silt-basins  are  omitted,  which  is  the 
case  with  the  narrower  and  more  irregular  walks,  the  drainage  of 
the  surface  of  the  walk  is  conducted  oif  to  the  ground  beyond,  or 
to  a  sod  gutter,  through  openings  in  the  border  of  the  walk  that 
are  made  at  suitable  points. 

804.  The  footway  is  formed  of  rubble  and  small  or  roughly 
broken  stones,  deposited  generally  eight  inches  deep  for  a  founda- 
tion, with  about  two  inches  of  gravel  spread  over  the  top  to  receive 
the  wear.     The  stones  are  such  as  are  obtained  from  the  earth 
excavations  in  grading  the  walk  and  adjoining  grounds,  or  from 
blasted  rock  and  bowlders,  or  field  stones  picked  off  the  surface  of 
the  ground,  or  cobble-stones  thrown  out  from  gravel  excavations, 
etc.,  as  may  be  found  convenient  in  any  case.     Blasted  or  quarry 
stones  are  preferable  when  they  can  be  had  in  sufficiently  small 
sizes,  and  without  incurring  the  expense  of  quarrying  them  specially 
for  the  purpose.     The  sizes  should  be  such  as  to  admit  of  making 
up  the  layer  of  eight  or  ten  inches  deep,  in  two  courses,  or  so  that 
no  single  stones  shall  reach  through  the  whole  layer,  and  prevent 
the  effectual  closing  of  interstices.     Quarry  stones  are  better  than 
field  stones,  for  the  reason  that  they  are  more  angular  and  irregular 
in  shape,  and  make  a  more  open  or  cellular  foundation  to  facilitate 
tha  drainage  and  prevent  the  action  of  frost. 

805.  A  bed  of  stones  laid  in  such  a  way  as  to  permit  the  sur- 
rounding spaces  to  be  filled  up,  either  by  the  wash  of  mud  along 
the  bottom,  or  by  the  sinking  of  the  stones  in  the  bottom  (in  con- 
sequence, frequently,  of  defective  drainage),  or  by  the  gravel  or  sur- 
face material  working  down  from  above,  is  but  little  better  than  a 
bed  of  natural  stony  ground,  for  it  absorbs  and  retains  all  the  water 
that  reaches  it,  until  it  fills  up  and  overflows  at  the  surface,  making 
the  walk  wet  and  spongy,  and  inviting  all  the  difficulties  and  de- 
teriorating results  that  it  is  a  principal   object   in   constructing 
walks  to  guard  against.     Walks  are  frequently  observed  that  have 


556  HIGHWAY    CONSTRUCTION. 

been  made  in  this  way — a  mass  of  stones  having  been  thrown  to- 
gether in  a  trench  on  wet  ground,  with  considerable  trouble  and 
expense,  and  the  unprotected  interstices  filled  solidly  with  mud  thut 
has  been  washed  in  from  time  to  time  (perhaps  mostly  during  the 
process  of  construction),  until  no  room  is  left  for  the  percolation 
of  water  from  the  surface,  and  the  saturated  bed  is  in  'a  condition 
to  be  operated  upon  to  the  fullest  extent  by  frost.  It  ought  not 
to  be  a  matter  of  surprise,  although  it  sometimes  is,  with  those  who 
make  such  walks,  that  they  do  not  give  satisfaction  at  all  commen- 
surate with  the  expense  and  labor  bestowed  upon  them. 

806.  When  the  layer  of  stones  is  formed  of  requisite  depth,  and 
some  pains  taken  to  regulate  and  adjust  the  surface  by  settling, 
breaking,  or  replacing  stones  that  are  too  large  or  that  project 
too  high,  and  filling  with   smaller  stones  or  covering  the  larger 
apertures,  a  coating  is  then  spread  over  of  quarry  chips  or  such 
finer  rubble  or  coarse  gravel  as  may  be  available.     In  case  such  ma- 
terials cannot  be  had,  soft,  shelly,  or  partially  decomposed  stones 
are  selected  and  broken  up  on  top  of  the  layer,  until  the  interstices 
are  sufficiently  closed  to  admit  of  following  the  process  with  a  light 
film  of  gravelly  loam  or  other  coarse  earth,  which  latter  material, 
after  being  evenly  distributed  and  moistened  is  well  rolled  by  hand- 
rollers.     This  prepares  the  surface  of  the  bed — when  the  work  is 
carefully  and  thoroughly  performed — for  the  reception  of  the  final 
covering  of  gravel. 

807.  The  perfection  of  the  work  consists,  up  to  this  point,  in 
forming  a  stable  and  unyielding  foundation,  with  the  interstices  of 
the  main  body  of  stones  kept  free  and  unobstructed,  and  a  covering, 
to  support  and  retain  the  superincumbent  gravel,  of  the  least  thick- 
ness and  density  that  will  enable  it  to  serve  its  purpose.    A  fair  test 
is  afforded  of  the  sufficiency  of  the  surfacing  material  by  letting  the 
work  stand,  after  the  rolling  is  done,  until  it  has  been  exposed  a 
few  days  to  the  weather :  if  it  sinks  away  into  the  stones  below, 
forming  holes  and  leaving  the  stones  naked  and  roughly  project- 
ing, it  shows  that  enough  material  has  not  been  added,  and  such 
spots  should  be  well  repaired;  if  it  retains  water  (from  rain),  form- 
ing a  muddy  surface  that  does  not  filter  away  and  dry  out  readily, 
it  shows  that  more  earthy  material  has  been  used  than  is  beneficial. 
The  proper  surfacing  of  the  bed  of  stones  will  not  ordinarily  add 
much  to  the  average  depth  of  the  layer,  just  covering  the  highest 


FOOTPATHS,  CURBS,  GUTTERS.  557 

points  of  the  stones,  and  filling  over  smoothly  the  intervening  in- 
equalities, so  that  the  gravel,  when  it  is  applied  above,  will  have  a 
uniform  depth  and  conform  to  the  desired  crowning  shape  of  the 
walk. 

808.  If  gutters  are  required  for  the  walk,  the  foundations  for 
them  are  prepared  by  using,  in  the  outer  edges  of  the  stone  filling, 
smaller  stones  and  gravel  for  the  better  support,  and  to  facilitate 
the  setting  of  the  gutter  stones. 

809.  The  gravel  is  deposited  on  the  walk  two  or  three  inches 
deep,  the  coarser  part  being  raked  forward  into  the  bottom  of  the 
layer,  and  such  pebbles  as  are  too  large  picked  off.     When  evenly 
adjusted,  a  film  of  sandy  or  clayey  loam  is  spread  over  the  surface 
and  lightly  raked  in  to  aid  the  binding  effect,  and  after  the  whole  is 
moderately  watered  or  moistened,  the  completing  process  of  rolling 
and  compacting  is  commenced.      This  is  done,  on  the  principal 
walks,  by  a  roller  drawn  by  a  horse;  on  narrow  walks  and  those 
having  greater  acclivities,  regularities,  rustic  steps,  etc.,  it  is  done 
by  a  roller  of  less  weight,  drawn  by  hand,  by  two,  three,  or  four 
men,  as  the  case  may  be.     As  the  rolling  proceeds,  a  man  follows 
with  a  rake,  to  correct  inequalities  and  keep  the  binding  material 
equally  diffused  through  the  gravel,  and  to  add  more  of  such  mate- 
rial, from  time  to  time,  as  may  prove  to  be  necessary.     Judgment 
and  expertness  are  required  to  manage  this  business  well.     Dull  or 
unpracticed   men  will  waste   their   time  at  it.     The  quantity  of 
binding  material  that  is  judicious  to  use  will  vary  sometimes  with 
each  load  of  gravel :  if  too  much  is  used,  or  if  it  is  unevenly  and 
carelessly  spread,  it  will  produce  an  imperfect  surface,  and  it  will 
take  considerable  time  and  labor  to  correct  after  the  walk  is  brought 
into  use.     If  the  gravel  is  fine  and  filled  with  dirt,  or  if  the  grains 
are  of  a  soft,  friable  quality,  it  will  not  need  as  much  foreign  mate- 
rial added  to  make  it  bind  as  when  it  is  clean  and  hard :  it  may 
contain  such  a  quantity  of  earthy  matter,  however  (as  is  frequently 
the  case),  as  to  make  it  necessary  to  free  it  from  a  portion  of  the 
binding  substance  by  screening,  rather  than  to  add  to  it :    such 
gravel  should  not  be  used  if  better  can  be  had.    All  muck,  top-soil, 
and  vegetable  or  fertilizing  matter  should  be  carefully  excluded 
from  both  the  gravel  and  the  binding  material,  to  prevent  the 
growth  of  grass  in  the  walk.    The  gravel  that  has  been  used  in  the 
Central  Park  walks  has  generally  been  of  a  sharp,  hard  quality,  and 
more  than  usually  free  from  dirt,  and  it  has  been  found  that  it 


558  HIGHWAY    CONSTRUCTION. 

would  bear  an  average  intermixture  of  about  one  fifth  its  bulk  of 
loamy  or  sandy  earth  to  give  it  the  requisite  binding  property.  If 
more  than  this  was  added,  the  work  of  rolling  and  packing  would 
be  facilitated,  but  the  surface  of  the  walk  would  absorb  and  retain 
water,  and  become  muddy  after  a  rain;  if  less  was  added,  the  roll- 
ing, although  it  might  be  thoroughly  done,  would  not  suffice  to 
make  a  surface  that  would  remain  firm  in  dry  weather. 

810.  The  elfect  of  the  proper  adjustment  of  these  points,  the 
selection  of  a  good  quality  of  gravel,  the  judicious  use  of  the  bind- 
ing material,  and  the  raking,  shaping,  and  rolling,  is  to  produce  a 
walk  that  is  agreeable  at  all  times :  not  muddy  or  slimy  after  a  ram.* 
or  loosened  so  that  the  foot  sinks  into  it  when  it  becomes  very  dry, 
or  much  subject  to  dust. 

With  care  and  some  sleight  in  the  raking,  before  and  after  the 
rolling  is  commenced,  the  finer  gravel  and  sand  will  be  worked  to 
the  top  and  the  coarser  pebbles  buried  in  the  bottom  of  the  layer, 
preventing  the  disagreeable,  feeling  that  is  caused  by  walking  over 
a  coarse  or  unequal  surface. 

811.  In  investigating  the  subject  of  walk  drainage  and  gutters,, 
in  the  early  stage  of  the  Park  work,  experiments  were  tried  in 
order  to  ascertain  if  some  better  or  cheaper  or  less  objectionable 
description  of  gutter  could  be  devised  than  those  in  common  use. 
Although  the  results  attained  were  not  such  as  to  warrant  the  adop- 
tion upon  the  very  uneven  grounds  of  the  Park  of  any  of  the  kinds 
of  gutter  experimented  upon,  yet  they  may  afford  some  hints  and 
possess  sufficient  interest  to  be  worthy  of  mention. 

The  principal  kinds  were  as  follows: 

(1)  Cement  or  concrete  gutter. 

(2)  Composition  gutter. 

(3)  Iron  gutter. 

(4)  Wood  gutter. 

Nos.  1  and  2  were  open  gutters.  No.  1  was  composed  of  a  con- 
crete consisting  of  two  parts  of  gravel  and  sand  and  one  part  of 
cement  laid  on  a  filling  (adjoining  a  walk  east  of  the  Mall),  of 
broken  stone  and  gravel  of  about  9  inches  in  depth.  The  concrete 
was  deposited  2  to  3  inches  thick,  and  moulded  by  the  aid  of  a 
wooden  implement  drawn  over  it  into  the  desired  form.  The 
gravel  of  the  walk  and  the  side  border  were  closed  up  to  it  on 
either  side,  and  completed  the  process. 


FOOTPATHS,  CURBS,  GUTTERS.  559 

This  gutter  was  comparatively  cheap  and  easy  of  construction, 
and  appeared  in  all  respects,  as  regards  utility,  well  adapted  to  the 
purpose.  After  exposure  to  the  weather  for  a  time,  it  became 
lighter  in  color  than  the  gravel  of  the  walk,  owing  to  the  cement 
which  entered  into  its  composition.  The  objection  to  it  at  the 
time  of  trial  (1859)  was  the  uncertainty  of  its  durability,  together 
with  the  general  objection  to  all  open  or  surface  gutters — that  it 
gave  too  marked  and  formal  an  outline  to  the  walk.  The  sample 
is  still  in  its  original  position.  It  has  improved  in  respect  to  color, 
and  has  been  but  little  affected  by  the  changes  of  weather  or  frost 
or  by  wear. 

No.  2,  composition  gutter,  east  side  of  "the  Ramble,"  was  made 
in  a  similar  manner  to  No.  1  as  to  form  and  dimensions,  but  the 
materials  used  and  its  manipulation  were  not  disclosed  by  the  gen- 
tleman who  introduced  the  sample  and  supervised  its  construction 
(Gen.  Asboth).  The  principal  defect  of  this  gutter  seemed  to  be 
the  contraction  of  the  materials,  which  separated  on  exposure  into 
broken  sections — the  action  of  frost  and  other  causes  tending  to 
increase  it  and  displace  the  parts.  It  was  also  open  to  the  general 
objection  mentioned  to  all  formal  gutters. 

No.  3,  iron  gutter,  was  made  of  light  sheet-iron,  in  sections  of 
U-form,  with  a  perforated  movable  lid  or  cover.  The  design  was 
to  make  it  a  concealed  gutter  by  sinking  it  along  the  edges  of  the 
walk  and  covering  it  over  with  a  light  layer  of  gravel — the  surface- 
water  to  percolate  through  the  gravel  and  the  perforations  in  the 
lid  into  the  gutter,  and  thence  pass  off  as  through  a  pipe.  This 
sample,  as  far  as  tried,  indicated  that  it  might  be  made  to  operate 
well  in  ordinary  cases  of  moderate  drainage  and  not  too  great  incli- 
nation of  the  walk,  but  it  was  considered  to  be  subject  to  too  many 
contingencies  for  general  use. 

No.  4,  wood  gutter,  was  constructed  upon  the  same  principle  as 
No.  3,  with  the  substitution  of  wood  for  iron.  It  was  a  mere  wooden 
trough  with  a  perforated  lid,  the  wood  having  been  subjected  to  a 
process  to  give  it  greater  than  ordinary  durability.  It  was  apparent 
that  it  was  inferior  to  the  iron  gutter  (though  much  cheaper),  and 
its  general  want  of  adaptability  was  considered  as  decisive  against 
it. 

A  method  of  macadamizing  gutters  of  the  common  (open)  form, 
was  tried  in  order  to  obtain  a  gutter  that  would  blend,  better  than. 


560  HIGHWAY   CONSTRUCTION". 

ordinary  paved  cobble-stone  gutters,  with  the  gravel  of  the  walk, 
and  not  present  the  usual  contrasts  of  color  and  kind  of  material, 
but  it  was  found  impracticable  by  ordinary  means  to  give  the 
materials  sufficient  compactness  and  cohesion  to  resist  long  the 
action  of  a  current  of  water.  The  same  process  was  tried  for  the 
surface  of  a  narrow  walk,  on  steep  ground,  where  it  was  difficult  to 
make  the  gravel  remain  during  rains,  and  with  the  same  results. 

These  experiments  (although  not  wholly  failures)  serve  to  show 
that  the  safest  and  probably  the  most  practicable  means  that  can  be 
adopted  for  the  drainage  of  walks  in  general  are  such  as  have  been 
gradually  brought  into  use  in  the  Park,  in  the  manner  that  has  been 
previously  described. 

812.  General  Directions  for  the  Construction  of  Gravel  Walke. 

(1)  Excavate  a  trench  the  width  intended  for  the  walk,  ten  to 
twelve  inches  deep,  leaving  the  bottom  even  and  regular  and  slightly 
crowning  in  the  centre,  unless  the  walk  is  to  be  quite  a  narrow  one. 
If  the  ground  is  not.  hard  and  firm,  pass  a  garden-roller  a  few  times 
over  it.     If  it  is  wet  and  heavy,  lay  a  line  of  1^-inch  drain-tile 
(using  collars)  along  the  walk  as  near  the  centre  as  practicable,  and 
at  a  sufficient  depth  to  be  below  the  reach  of  frost. 

(2)  Fill  the  space  excavated  for  the  walk  six  to  nine  inches  deep 
with  field  or  quarry  stones,  placing  the  smallest  on  top.     Select  the 
softest  and  easiest  stones  to  break,  and  hammer  them  up  on  top  of 
the  stone  filling  until  the  interstices  are  sufficiently  filled  to  exclude 
the  gravel.     Kotten  or  partially  decomposed  stones  will  answer  well 
for  this  purpose,  or,  if  this  material  is  not  convenient,  use  a  light 
layer  of  gravelly  loam  or  hardpan.     The  surface  will  be  further 
improved,  previous  to  putting  on  the  gravel,  by  sprinkling  it  and 
going  over  it  a  few  times  with  the  roller.     The  object  of  the  process 
thus  far  is  to  secure  a  firm,  well-drained  foundation  for  the  walk, 
having  the  surface  interstices  of  the  stone  filling  sufficiently  closed 
to  prevent  the  gravel  from  running  down  and  filling  up  the  voids 
below,  and  yet  leaving  free  vent  for  surface-water  to  percolate 
through. 

(3)  If  the  stone  filling  is  well  prepared  in  this  way,  and  the  sur- 
face made  even, — no  points  of  large  stones  projecting,  etc., — two 
inches  in  depth  of  hard  fine  gravel  will  be  sufficient  to  complete 
the  walk.     In  applying  the  gravel  a  light  layer  should  at  first  be 
put  on  and  raked  over  evenly,  working  the  coarser  gravel  forward 


FOOTPATHS,  CURBS,  GUTTERS.  561 

into  any  interstices  or  inequalities  of  the  stone  filling.  Moisten  this 
layer  and  roll  it  down  firmly  and  evenly.  The  second  and  last  layer, 
to  make  the  most  complete  and  agreeable  surface,  should  be  passed 
through  a  screen  the  meshes  of  which  are  not  more  than  ^g-  of  an 
inch  wide,  and  care  should  be  taken  in  applying  it  not  to  rake  up 
the  first  layer,  and  to  spread  it  evenly — holding  the  handle  of  the 
rake  nearly  perpendicular.  If  it  is  not  screened,  more  pains  must 
be  taken  (with  a  fine  rake)  to  exclude  from  the  surface  gravel  that 
is  too  coarse  and  unequal  in  size  to  be  agreeable  to  the  foot.  Next 
and  lastly,  sprinkle  and  roll  the  whole  thoroughly.  The  gravel 
should  not  be  drenched,  but  only  made  moist  or  damp  in  order  to 
pack  well  under  the  roller.  Until  the  walk  has  had  some  wear,  it 
will  be  necessary,  after  dry  weather,  to  trim  the  surface  anew  with 
the  back  of  the  rake,  and  to  repeat  the  rolling  occasionally.  Roll 
after  a  light  rain,  but  never  when  the  gravel  is  dry  or  when  too  wet, 

(4)  A  slight  intermixture  of  clay  or  loam  with  the  gravel  will 
serve  to  make  it  pack  or  "  bind  "  more  firmly  when  desirable,  and 
with  less  use  of  the  roller;  but  this  should  be  done  with  moderation, 
and  no  vegetable  mould  should  be  introduced  to  encourage  the 
growth  of  grass  or  weeds.     It  is  a  great  advantage  to  procure  pure 
.gravel :  its  freedom  from  earthy  or  vegetable  matter  prevents  not 
only  vegetation  from  taking  root,  but  the  liability  to  dust  in  dry 
weather  and  a  muddy  or  slippery  surface  in  wet  weather.     It  also 
prevents  the  action  of  frost.     It  is  better,  therefore,  to  avoid  any 
intermixture  of  other  substances  that  will  defeat  these  objects. 

(5)  The  surface  of  a  walk  should  be  a  little  crowned  in  the 
centre,  and  should  be  provided  with  outlets  through  the  grass 
borders,  at  suitable  points,  to  carry  off  sudden  accumulations  of 
water.     Where  the  walk  has  much  inclination,  and  also  where  the 
outside  drainage  from  adjacent  ground  is  liable  to  be  brought  to  it, 
more  frequent  outlets,  cross-drains,  etc.,  must  be  made. 

(6)  If,  for  any  considerable  distance  along  the  walk,  drainage- 
water  from  sudden  rains  cannot  be  conveyed  away  from  it  securely 
by  these  means,  gutters  must  be  made.     These  can  be  made  in  a 
variety  of  ways,  but  there  are  no  gutters  that  give  more  permanent 
satisfaction,  at  a  moderate  cost,  than  those  formed  neatly  with  small 
cobble-stones.     Suitable  stones  for  the  purpose  can  generally  be 
selected  from  the  gravel  delivered  for  the  walk,  or  from  the  pit 
.from  which  it  is  obtained. 


562  HIGHWAY    CONSTRUCTION". 

(7)  A  system  of  walks,  extending  over  a  large  area  of  ground 
that  is  not  naturally  adapted  to  easy  surface  drainage,  must  have 
one  or  more  main  under-drains  with  subordinate  or  branch  drains, 
entering  them  from  various  points  of  the  system,  and  with  inlets 
from  the  gutters  of  the  walks,  silt-basins,  etc.,  all  of  which  must 
be  adapted  to  the  local  circumstances  in  each  case  by  special  study 
or  survey,  and  no  general  rule  can  therefore  be  given  for  their 
treatment. 

(8)  A  walk  can  be  cheaply  made  on  light,  well-drained  soil  by 
simply  removing  the  turf  to  the  depth  of  three  or  four  inches  and 
filling  the  space  with  gravel,  raking  the  coarse  forward  into  the 
bottom  and  leaving  the  fine  on  top.     One  half  of  the  gravel,  in  this 
case  (in  the  bottom),  may  be  of  inferior  quality. 

813.  Curbstones. — Curbstones  are  employed  for  the  outer  side 
of  the  footways  to  sustain  the  coverings  and  form  the  gutter. 
Their  upper  edges  are  set  flush  with  the  footwalk  pavement,  so 
that  the  water  can  flovf  over  them  into  the  gutters. 

The  disturbing  forces  which  the  curb  has  to  resist  are:  (1)  The 
pressure  of  the  earth  behind  it,  which  is  frequently  augmented  by 
piles  of  merchandise,  building  materials,  etc.  This  pressure  tends 
to  overturn  it,  break  it  transversely,  or  move  it  bodily  on  its  base. 
(2)  The  pressure  due  to  the  expansion  of  freezing  earth  behind 
and  beneath  it.  This  force  is  most  frequent  where  the  sidewalk  is 
partly  sodded  and  the  ground  js  accordingly  moist.  Successive 
freezing  and  thawing  of  the  earth  behind  the  curb  will  occasion  a. 
succession  of  thrusts  forward,  which,  if  the  curb  be  of  faulty  design, 
will  cause  it  to  incline  several  degrees  from  the  vertical.  (3)  The 
concussions  and  abrasions  caused  by  the  traffic.  To  withstand  the 
destructive  effect  of  wheels,  curbs  are  faced  with  iron  at  certain 
places  in  the  streets  of  London,  and  a  concrete  curb  with  a  rounded 
edge  of  steel  has  been  patented  and  used  to  some  extent  in  this 
country.  Fires  built  in  the  gutters  deface  and  seriously  injure  the 
curb.  Posts  and  trees  set  too  near  the  curb, tend  to  break,  displace, 
and  destroy  it. 

The  use  of  drain-tiles  under  the  curb  is  a  subject  of  much  dif- 
ference of  opinion  among  engineers.  Where  the  subsoil  contains 
water  naturally,  or  is  likely  to  receive  it  from  outside  the  curb- 
lines,  the  use  of  drains  is  of  decided  benefit,  but  great  care  must 


FOOTPATHS,  CURBS,  GUTTERS.  563 

be  exercised  in  jointing  the  drain- tiles  lest  the  soil  shall  be  loosened 
and  removed  and  cause  the  curb  to  drop  out  of  alignment. 

The  materials  employed  for  curbing  are  the  natural  stones,  as 
granite,  sandstone,  etc.,  artificial  stone,  fire-clay,  and  cast  iron. 

The  dimensions  of  curbstones  vary  considerably  in  different 
localities,  and  according  to  the  width  of  the  footpaths :  the  wider 
the  path  the  wider  should  be  the  curb.  It  should,  however,  never 
be  less  than  8  inches  deep,  nor  narrower  than  4  inches.  Depth  is 
necessary  to  prevent  the  curb  turning  over  towards  the  gutter.  It 
should  never  be  in  less  lengths  than  3  feet.  The  top  surface  should 
be  bevelled  off  to  conform  to  the  slope  of  the  footpath.  The  front 
face  should  be  hammer-dressed  for  a  depth  of  about  6  inches,  in 
order  that  there  may  be  a  smooth  surface  visible  against  the  gutter. 
The  back  for  3  inches  from  the  top  should  be  also  dressed,  so  that 
the  flagging  or  other  paving  may  butt  fair  against  it.  The  end- 
joints  should  be  cut  truly  square,  the  full  thickness  of  the  stone  at 
the  top,  and  so  much  below  the  top  as  will  be  exposed;  the  remain- 
ing portion  of  the  depth  and  bottom  should  be  roughly  squared,  and 
the  bottom  should  be  fairly  parallel  to  the  top. 

Curbstones  should  be  inspected  before  they  are  set,  and  marks 
showing  the  rejected  stone  should  be  placed  on  the  face  in  such 
position  that  they  will  be  exposed  to  view  should  the  stone  be 
placed  in  position.  For  marking  the  stones  white-lead  mixed  with 
turpentine  is  the  best;  it  is  not  easily  washed  off,  is  conspicuous, 
and  is  not  dirty  to  handle. 

814.  Setting  Curb  requires  care  and  an  experienced  workman, 
for  as  it  is  set  dry,  great  care  must  be  exercised  to  set  it  true  to 
level  and  line.  It  must  be  well  rammed  and  bedded  or  it  will  sink, 
turn  slightly  over  or  move,  even  months  after  it  has  been  set. 
Curbstones  carelessly  set  will  never  present  a  pleasing  appearance. 

Curbstones  to  be  set  in  concrete  should  be  first  set  and  blocked 
in  position  on  grade  and  line.  The  blocking  should  be  done  with 
brick,  paving-stones,  or  other  imperishable  material. 

The  inspectors  should  watch  this  work  carefully,  and  see  that 
the  trenches  are  so  prepared  that  the  full  amount  of  concrete  may 
be  deposited  and  tamped  solidly  into  place. 

In   tamping  the   concrete   under    and    around   curbstones,   a 


564  HIGHWAY    CONSTRUCTION. 

wooden  tamper  made  of  a  piece  of  seasoned  oak  two  inches  by  four 
inches,  about  five  feet  long,  shod  with  quarter-inch  iron,  makes  an 
excellent  tool  for  this  purpose. 

The  concreting  of  the  curbs  (which  should  be  done  in  advance 
of  the  roadway  concreting)  is  best  performed  by  first  filling  under- 
neath from  the  roadway  side,  then  upon  the  face  and  back  up  to 
the  grade  of  the  roadway,  then  filling  up  behind  the  stones  to 
the  required  height,  removing  all  blocking  from  behind  the  stones 
as  the  concrete  is  tamped  in,  taking  care  not  to  disturb  the  aline- 
ment  of  the  curb  and  to  see  that  every  space  is  filled  solid  with  the 
concrete. 

In  setting  curbstones  it  is  well  to  keep  the  ends  from  actual 
contact.  For  this  purpose  strips  of  £-inch  iron  can  be  tem- 
porarily inserted  between  the  ends  as  they  are  set  and,  after  the 
roadway  concrete  is  laid,  the  joints  should  be  filled  with  a  thin 
grout  composed  of  equal  parts  of  Portland  cement  and  sand. 
This  should  be  done  by  first  pressing  a  small  amount  of  stiff 
mortar  into  the  joints  at  the  face  and  back  and  then  pouring  the 
grout  in  from  the  top  until  the  joint  is  full.  A  small  wire  used  as 
a  probe  will  aid  materially  in  securing  a  full  joint.  If  these  joints 
are  not  filled  solid,  but  simply  smeared  over  the  surface  with  a 
little  mortar  which  only  penetrates  a  half  inch  or  less,  it  will  only 
be  a  question  of  a  short  time  when  it  will  drop  off  and  leave  a 
cavity  between  the  stones.  In  order  to  detect  defective  work  in 
filling  the  joints,  the  inspector  should,  after  the  cement  has  hard- 
ened, test  each  joint  by  tapping  on  it  with  a  small  piece  of 
metal ;  the  sound  will  reveal  the  presence  of  cavities. 

815.  In  localities  where  stone  is  not  obtainable,,  artificial  stone, 
fire-clay  curb,  and  cast  iron  afford  excellent  substitutes.  Artificial 
stone  under  the  name  of  Asbestine  Building-stone  is  used  in  some 
of  the  Western  cities;  it  is  manufactured  from  German  Portland 
cement,  sand,  and  broken  stone. 

Fire-clay  curbing  is  extensively  used  with  brick  pavements  ; 
some  of  the  usual  forms  are  shown  in  Figs.  162  to  166. 

Cast  iron  is  employed  in  some  cities  in  France;  it  is  cast  in 
L-shaped  sections,  as  shown  in  Fig.  167. 


FOOTPATHS,    CUBES,    GUTTERS.  565 

Curbstones,  gutters,  etc.,  are  manufactured  in  Germany  from 
the  following  : 

Clay 9H  parts 

Iron  filings 3 

Common  salt k 2       " 

Potash ,....  l£     " 

Ash  of  elder  or  willow  wood 2      " 

Various  colors  are  produced,  as  follows : 

Violet-brown by  2  parts  of         pyrolusite         to  100  parts 

Violet "   1     "      "  "  "     "      " 

Green "   1     "      "        copper  scales       "     "       " 

Blue "   1     "      "     oxide  of  cobalt      "     "       " 

Yellow "   2     "      "  oxide  of  antimony  "     "       " 

MONOLITHIC  CURB  AND  GUTTER. — Parkhurst  Combined  Curb 
and  Gutter.— This  curb  and  gutter  is  composed  of  Portland  cement, 
trap-rock  crushed  and  screened  to  different  grades  of  fineness,  and 
sand.  It  is  manufactured  in  place  on  the  ground,  and  when  com- 
pleted the  curbing  is  6  inches  thick,  varying  as  desired  from  5  to  10 
inches  high,  with  a  gutter  12  inches  wide.  It  forms  a  monolith  on 
each  block,  weakened,  however,  by  cuts  extending  partially  through 
it  at  intervals  of  about  5  feet,  to  allow  for  expansion  and  disturbance 
caused  by  frost  or  other  agent. 

816.  Specifications   for    Standard   Granite    Curb   (Washington, 

D.  C.). — The  curbing  must  be  of  good  and  acceptable  texture  and 
color,  dressed  12  inches  on  the  face,  3  inches  on  the  back,  and 
chiselled  6  inches  deep  on  the  joints,  with  no  projections  beyond  the 
chiselled  portion  of  the  joint;  the  joint  to  be  at  right  angles  to  the 
face  and  top  surface;  the  top  surface  to  be  bevelled  £  inch;  the 
face  and  top  to  be  plane  surfaces,  without  depressions  or  irregulari- 
ties. The  length  must  not  be  less  than  6  feet,  depth  not  less  than 
20  inches  nor  more  than  24  inches  in  any  portion  of  a  piece,  and 


56G 


HIGHWAY    CONSTRUCTION. 


thickness  6  inches.  The  bed  of  the  curb  must  average  not  less 
than  6  inches  in  width,  and  no  excessive  protuberance  will  be  al- 
lowed on  the  sides. 

817.  Special  8  by  8  Inches  Granite  Curb.— The  curbing  must  be 
of  suitable  and  acceptable  color  and  texture,  dressed  on  top  and  the 
full  depth  on  the  face,  and  3  inches  deep  on  back.     The  top  sur- 
face will  be  bevelled  J  of  an  inch.     The  face  and  top  to  be  plane 
surfaces,  without  bends,  twists,  depressions,  cups,  or  other  irregu- 
larities.    It  will  be  8  inches  thick,  not  less  than  8  inches  nor  more 
than  12  inches  deep,  and  no  piece  less  than  6  feet  long.     The  joint 
will  be  chiselled  throughout.     The  bed  will  be  rough-dressed  to 
give  secure  bearing. 

818.  Specifications  for   Bluest  one  Curb  (Washington,  D.  C.).— - 
The  curbing  must  be  best  North  River  bluestone,  dressed  12  inches 
on  the  face  and  3  inches  on  back,  and  chiselled  6  inches  deep  on 


FIRE-CLAY  CURB. 


FIG,  162, 


FIG,  163, 


FIG,  164, 


FIG.  165,  FIG,  166, 


FIG,  167,— IRON  CURB. 


FOOTPATHS,  CURBS,  GUTTERS,  507 

the  joints,  with  no  projection  beyond  the  chiselled  portion  of  the 
joint;  the  joints  to  be  at  right  angles  to  the  face  and  top  surface. 
The  top  surface  will  be  bevelled  £  of  an  inch;  the  face  and  top  to 
be  plane  surfaces,  without  bends,  twists,  depressions,  cups,  or  other 
irregularities.  The  length  must  not  be  less  than  4  feet,  depth  not 
less  than  20  inches,  and  not  more  than  24  inches  in  any  portion  of 
;i  piece,  and  thickness  5  inches.  Each  piece  must  have  a  bed  not 
less  in  area  than  the  dressed  portion  of  the  curb,  and  no%  'excessive 
protuberance  on  the  sides. 

819.  Circular  Curb. — Circular  curb  will  conform  in  all  respects 
to  the  specifications  for  straight  curb,  except  that  it  will  be  cut  to 
the  required  radius.     It  must  be  cut  to  such  lengths  that  three 
pieces  will  make  a  90-degree  curve. 

820.  Specifications  for  Curbstones  (New  York). — The  curbstones 
•shall  be  of  the  best  quality  of  North  River  bluestone,  5  inches  thick, 
and  not  less  than  4  nor  more  than  8  feet  long,  and  20  inches  deep,  cut 
•and  smooth  dressed  on  the  front  to  a  depth  of  14  inches,  bevelled 
on  top  to  the  slope  of  the  sidewalk.     Ends  shall  be  accurately 
squared,  so  as  to  make  close  joints  the  whole  depth. 

821.  Specifications  for  Setting  Curb  (Washington,  D.  C.).— The 
trench  will  be  dug  24  inches  deep  and  18  inches  wide,  to  permit  a 
thorough  ramming.     A  bed  of  gravel  4  inches  deep  will  be  laid  in 
the  bottom  of  the  trench  and  thoroughly  consolidated.     On  this 
bed  the  curb  will  be  laid  to  level  and  grade  with  close  joints  and 
•even  and  continuous  surfaces.     The  ditch  will  then  be  filled  with 
gravel,  the  first  filling  to  be  not  more  than  3  inches  deep,  be  well 
rammed  by  rammers  or  bars  so  as  to  give  the  curb  a  solid  bearing 
under  its  entire  length.     Other  layers  will  then  be  rammed  in  the 
ditch  to  within  10  inches  of  the  top  of  the  curb;  the  layer  for  each 
ramming  to  be  not  more  than  4  inches  deep. 

The  special  granite  curb  will  be  laid  on  a  foundation  of  hydraulic 
concrete,  as  shown  in  Fig.  168. 

On  the  gravel-bed  the  concrete  foundation  made  as  prescribed 
for  the  concrete  base  for  standard  asphalt-pavements  will  be  laid, 
This  concrete  base  will  be  laid  of  such  depth  as  to  permit  the 
granite  curb  (of  which  the  depth  will  vary  generally  from  3  to  12 
inches)  to  be  placed  upon  it  and  remain  at  the  proper  grade.  All 
spaces  remaining  between  the  curb  and  the  concrete  foundation 
will  then  be  carefully  rammed  completely  full  with  cement  mortar 


568 


HIGHWAY   COKSTRUCTIOtf. 


or  fine  concrete  suitable  for  the  purpose.  The  necessary  concrete  will 
then  be  added  to  bring  the  foundation  to  the  dimensions  shown  in 
the  cut.  The  work  of  setting  this  curb  will  be  done  by  competent 
stone-masons.  If  so  desired,  the  contractor  will  be  authorized  to 


FIG.  1  68.-GRANITE  CURB  (WASHINGTON,  D,  C.). 


•W.y/S/SSffftfflWYftWy 

//v///y/////,ti^///////,w< 


/'6" 

FIG.  1  69,— BLUESTONE  CURB. 

finish  the  foundation  in  front  of  the  curb  with  a  layer  of  binder,  as 
prescribed  for  the  intermediate  course  in  coal-tar  distillate  pave- 
ments, but  no  extra  allowance  will  be  made  for  such  work. 

822.  Specifications  for  Artificial  Stone  Curb  and  Gutter  (Wash- 
ington, D.  C.).— A  combination  curb  and  gutter  of  artificial  stone 


FOOTPATHS,    CURBS,    GUTTERS.  569 

on  concrete  foundation  will  be  laid  on  streets,  as  may  be  ordered  by 
the  Engineer  Commissioner.  The  curb,  gutter,  and  foundation 
will  conform  with  the  dimensions  given  on  drawings  on  file  in 
Engineer  Department.  The  concrete  foundation  will  be  composed 
of  the  same  materials  and  will  be  laid  in  the  same  manner  as  pre- 
scribed for  concrete  foundations  of  asphalt  pavements.  The  curb 
and  gutter  will  consist  of  fine  concrete  composed  of  one  part  Port- 
land cement,  two  parts  clean  sharp  sand,  and  three  parts  clean 
broken  stone  not  more  than  1  inch  in  their  largest  dimensions. 
The  exposed  surfaces  of  both  gutter  and  curb  will  be  coated  1£  inch, 
thick  with  a  cement  composed  of  three  parts  granulated  granite 
(the  fragments  being  of  such  size  as  to  pass  through  a  quarter-inch 
screen  and  free  from  all  dust),  and  two  parts  of  cement. 

The  cement  used  in  the  manufacture  of  the  curb  and  gutter 
must  conform  to  the  current  District  of  Columbia  specifications  for 
slow-setting  Portland  cement.  The  work  will  be  carried  on  uni- 
formly, and  the  whole  curb  completed  while  in  a  soft  and  plastic 
state,  so  that  it  will  become  a  homogeneous  solid  when  set.  While 
still  plastic  the  curb  and  gutter  will  be  saw-cut  at  intervals  of  8  to 
10  feet,  as  may  be  ordered,  to  allow  for  expansion  and  contraction, 
and  to  give  the  appearance  of  cut  stone. 

Contractors  may  use  such  methods  of  moulding  the  curb  into 
shape  as  they  may  deem  best  fitted  to  the  work.  The  curb  and 
gutter  when  set  must  conform  with  the  cross-section  shown  in 
drawing. 

A  conduit  for  electrical  conductors,  4  inches  wide  and  4  inches 
high,  will  be  left  at  the  base  of  the  curb  if  so  ordered  by  the 
Engineer  Commissioner.  Hand-holes,  to  give  access  to  this  conduit, 
will  be  left  at  intervals  of  50  feet,  more  or  less,  as  may  be  ordered, 
all  to  be  as  shown  on  the  drawings.  Man-holes  will  be  constructed 
near  each  cross-street  in  accordance  with  plans  and  specifications  on 
file  in  Engineer  Department.  The  exact  location  of  each  man-hole 
will  be  fixed  by  the  Engineer  Commissioner.  The  cost  of  these 
man-  and  hand-holes,  and  their  frames  and  covers,  must  be  included 
in  the  price  per  linear  foot  of  the  "combination  curb  and  gutter" 
with  electrical  conduit. 

The  curb  and  gutter  must  be  properly  protected  from  injury 
while  setting,  and  the  material  used  for  such  protection  must  be 
removed  within  twenty-one  days  from  the  completion  of  work,  if  so 
ordered. 


570 


HIGHWAY    CONSTRUCTION. 


The  contractor  is  required  by  law  to  guarantee  all  work  for  the 
period  of  five  years  from  the  date  of  the  completion  of  the  contract. 

823.  Specifications  for  Dressing   Old   Curb. — Old  curb  will  be 
dressed  by  the  contractors  for  street  improvements  whenever  ordered 
by  the  engineer. 

Contractors  will  employ  competent  stone-cutters  to  do  thewofk, 
and  will  be  allowed  the  actual  cost  of  the  labor  employed  plus  15 
per  cent,  for  tools,  sharpening  same,  and  supervision.  Certified 
pay-rolls  of  men  employed  and  amount  paid  will  be  required  for 
each  street. 

824.  Re-setting  Curbstones. — The  curbstones  along  the  line  of 
the  work  shall  be  readjusted  and  brought  to  the  grade,  and  lines 
given  by  the  engineer,  without  extra  charge  therefor.     All  curb- 
stones on  the  line  of  the  work  that  are  cracked  or  broken,  or  other- 
wise damaged,  shall  be  re-dressed  so  as  to  conform  practically  in 
form,  size,  and  quality  to  the  requirements  of  the  specifications  for 
new  curbstones.     New  stones  shall  be  furnished  when  necessary, 
without  extra  charge  therefor. 

825.  Hollow  sidewalk  curbs  are  shown  in  Figs.  170, 171;  they 
are  especially  designed  as  a  conduit  for  electric  wires  or  cables  or 
for  pipes.     They  are  the  invention  of  Mr.  E.  Greyson  Banner,  of 
London,  England. 

The  principle  is  shown  in  Eig.  170  in  its  simplest  form.  The 
block,  a,  may  be  of  concrete,  through  which  the  channels  cc  are 


Bg,170. 


HOLLOW  CURB. 


Fig.171.. 


moulded,  and  which  are  accessible  upon  the  removal  of  the  flag  b. 
This  flag  may  be  continuous  in  the  case  of  pipes,  but  for  wires,  etc., 
it  may  be  so  arranged  with  hand-holes  at  short  intervals. 

Fig.  171  is  a  modified  section  for  use  where  the  wires  are  to  be 
kept  at  a  distance  apart,  for  the  sake  of  greater  insulation,  each 
•  wire  having  a  separate  channel. 


FOOTPATHS,  CURBS,  GUTTERS. 


571 


The  curb  may  be  formed  in  place  or  manufactured  at  a  factory, 
in  which  case  the  blocks,  to  secure  alignment,  are  made  with  projec- 
tions on  one  end  which  fit  into  corresponding  recesses  on  the  other. 

826.  Gutters. — In  streets  covered  with  broken  stone,  a  stone 
gutter  is  necessary.  It  may  be  formed  of  either  stone  slabs  or  pav- 
ing-blocks, the  latter  being  the  better.  It  should  be  not  less  than 
18  inches  wide.  If  formed  of  paving-blocks,  the  blocks  should  be 
laid  with  their  length  parallel  to  the  curb,  bedded  on  gravel,  and 
well  grouted  in  with  bituminous  cement. 


!V|I|     <»    Vl     ,'.l: 

-,  '  '     l1  !        '''       -1  't     I'M'      I1     ',1       H 

I  M  ..  i1  |    n  .-,    ,  V  /I  <•  '',,  v(J,,i|\ 

1 

FIG.   172.    PLAN  SHOWING  MANNER  OF  LAYING 
GUTTER-STONES. 


When  stone  slaos  are  used,  they  should  be  not  less  than  3  feet 
long,  6  inches  thick,  and  from  10  to  15  inches  in  width.  They 
should  be  laid  alternately  (see  Fig.  172) ;  for  if  of  uniform  width, 
the  continuous  longitudinal  joint  between  the  gutter  and  the  rest 
of  the  pavement  will  quickly  wear  into  long  deep  ruts  or  grooves, 
which  causes  severe  strains  upon  the, running-gear  of  vehicles  when 
the  wheels,  having  once  entered  the  rut,  attempt  to  leave  it. 

The  gutter  should  have  the  same  slope  as  the  roadway,  and  the 
curb  should  show  seven  inches  or  more  above  it. 

In  streets  paved  with  asphalt  granite  blocks  or  bricks  the  same 
material  is  used  for  the  gutters;  the  blocks  being  laid  with  their 
length  parallel  to  the  curb,  instead  of  transversely  as  in  the  street 
itself. 

827.  Specifications  for  Laying  Cobble  Gutters  and  Crossings. — 
The  cobblestone  and  flagging  will  be  furnished  by  the 
along  the  line  of  the  work. 

The  materials  necessary  to  be  removed  shall  be  excavated  to  a 
depth  of  12  inches  below  the  top  line  of  the  proposed  gutter  or 
crossing  when  fully  packed.  Any  objectionable  or  unsuitable 
material  found  below  that  depth  must  be  removed,  and  the  space 
filled  with  clean  sand  or  gravel. 


572  HIGHWAY   CONSTRUCTION". 

All  holes  or  inequalities  shall  be  filled  to  a  proper  level  with  sand 
or  gravel  well  compacted  by  ramming  or  rolling.  Upon  the 
foundation  thus  prepared  shall  be  laid  a  bed  of  good  bank  gravel,  5 
inches  in  thickness,  thoroughly  compacted  by  rolling  or  ramming. 
Upon  this  shall  be  spread  a  layer  of  clean,  sharp  sand,  to  serve  as  a 
bed  for  the  paving-stones,  of  such  depth  as  may  be  required  to  bring- 
the  work  to  grade. 

The  cobblestones  shall  be  assorted  as  they  are  brought  upon  the 
ground,  and  no  stones  that  are  less  than  4  or  more  than  6  inches- 
long,  or  less  than  2  or  more  than  4  inches  wide,  shall  be  used,  and 
the  several  sizes  must  be  laid  so  as  to  make  an  even  surface  when, 
rammed.  When  thus  laid  the  stone  shall  be  immediately  covered 
with  clean,  fine  sand,  in  proper  quantities,  and  raked  until  the 
joints  become  filled  therewith;  the  stones  shall  then  be  thoroughly 
rammed  to  a  firm,  unyielding  bed  with  a  uniform  surface  and 
proper  grade. 

The  foundation  for  the  gutter  and  crossing-flag  shall  be  pre- 
pared in  the  same  manner  as  described  for  cobble,  upon  which  the 
flag  shall  be  laid  with  close  joints  and  settled  into  place  solidity  in 
such  a  manner  as  not  to  fracture  the  flag.  When  gutters  are  laid 
without  curb,  selected  stones  of  large  size  shall  be  laid  to  line  in  the 
position  and  at  the  height  that  the  curb  would  be  if  laid.  This 
course  must  be  laid  true  to  line  and  grade  and  with  especial  care. 
Gutters  will  generally  be  4  feet  wide,  with  12-inch  flagging  in  the 
centre.  * 

828.  Specifications  for  Brick  Gutters. — Whenever  ordered  on 
streets  to  be  paved  with  asphalt,  brick  gutters  will  be  laid.  The 
materials  necessary  to  be  removed  shall  be  excavated  to  a  depth  of  8  £ 
inches  below  the  top  line  of  the  proposed  gutter.  Any  objectionable 
or  unsuitable  material  found  below  that  depth  must  be  removed  and 
the  space  filled  with  clean  sand  or  gravel.  All  holes  or  inequalities- 
shall  be  filled  to  a  proper  level  with  sand  or  gravel  well  compacted 
by  rolling  or  ramming.  Upon  the  foundation  thus  prepared  there 
will  be  placed  a  layer  of  hydraulic-cement  concrete  4  inches  in 
thickness.  This  concrete  layer  shall  conform,  in  all  respects  ex- 
cept depth,  with  the  concrete  base  as  specified  herein  for  standard 
asphalt  pavements.  Upon  the  concrete  base  so  prepared  paving- 
bricks  shall  be  placed  on  edge  with  their  lengths  at  right  angles  to 
the  curb  and  breaking  joints  in  the  direction  of  the  curb.  The 


FOOTPATHS,    CURBS,    GUTTERS.  573 

outer  edge  of  the  gutter  shall  be  left  with  alternately  projecting 
bricks  to  tooth  into  the  asphalt  pavement. 

The  bricks  must  be  so  laid  that  the  upper  surface  will  be  smooth 
and  at  the  proper  grade. 

Immediately  after  the  completion  of  the  asphalt  pavement  ad- 
jacent to  the  gutter,  hot  paving-tar  shall  be  poured  into  the  joints 
of  the  bricks  until  it  rises  to  the  surface.  The  gutter  shall  then  be 
covered  with  a  sprinkling  of  sharp  dry  sand.  If  so  ordered,  instead 
of  the  hot  paving-tar  a  grouting  of  Portland  cement  and  sharp 
sand  in  equal  proportions,  mixed  with  a  sufficiency  of  water  to 
make  a  thin  grouting,  will  be  used.  The  bricks  for  this  gutter- 
paving  will  be  furnished  by  at  its  property  yards, 
and  hauled  thence  to  the  site  of  the  work  by  the  contractor  for 
laying  them. 

Bricks  for  gutters  may  be  furnished  by  the  at  the  site 

of  the  work.  A  separate  bid  is  requested  for  the  work  if  bricks  be 
so  furnished. 

829.  Specifications  for  Gutter-stones. — The  gutter-stones  to  be 
of  stone,  not  less  than  4  feet  long  and  10  to  16  inches  wide, 
and  4  inches  thick  throughout ;  to  have  a  smooth  surface  free  from 
winds,  seams,  or  other  imperfections;  to  be  cut  and  squared  so  as 
to  form  close  joints  with  each  other  and  with  the  curb. 

The  stones  shall  be  laid,  at  the  grade  furnished,  on  a  bed  of  sand 
2  inches  thick.  The  joints  of  the  stones  shall  break  joint  with  the 
joints  of  the  curb.  The  stones  shall  be  laid  narrow  and  wide  alter- 
nately. The  joints  shall  be  filled  with  a  bituminous-cement  or 
Portland-cement  mortar. 

830.  Crossing  or  Bridge-stones. — Street-crossings  are  footways 
provided  for  pedestrians;  they  are  formed  of  two  or  more  rows  of 
stone  slabs,  usually  with  one  or  more  rows  of  paving-blocks  between 
them. 

The  stone  used  for  crossings  should  not  be  less  than  3  feet  long, 
10  inches  wide,  and  6  inches  thick,  with  the  top  surface  hammer- 
dressed,  the  ends  cut  to  a  bevel  of  about  15°,  as  shown  in  Fig.  174, 
and  dressed  so  as  to  form  a  close  joint  for  the  full  depth  of  the  stone. 
The  reason  for  bevelling  the  joints  is  to  cause  the  traffic  to  travel 
across  the  joint  instead  of  along  it,  and  thus  prevent  the  formation 
of  the  ruts  which  happens  with  right-angled  joints.  The  bevelled 
joints  must  point  towards  the  centre  of  the  intersection,  otherwise 
the  desired  result  will  not  be  obtained,  and  ruts  will  be  formed. 


•574 


HIGHWAY   CONSTRUCTION. 


FIG.  173.     SECTION  AT  CROSSING,  SHOWING  GUTTER 
PAVED  WITH  STONE  BLOCKS. 


I   .   I 


J L 


*r 


,> 


FlG.  174.     PLAN  OF   CROSSING,  SHOWING    BEVELLED 

JOINTS. 


FlG.  175.    SECTION  OF  CROSSING  SHOWING  GUTTER 
PAVED  WITH  A  SINGLE  STONE. 


FOOTPATHS,  CURBS,  GUTTERS. 


575 


Sandstone  is  superior  to  granite  for  this  purpose. 

At  street-crossings  the  bridge-stones  should  be  kept  level  with 
the  curb  so  that  pedestrians  may  step  off  the  path  onto  the 
crossing  without  any  drop  (see  Figs.  173  to  176). 


FIG.   176.    COVERED  GUTTER. 

831.  Specifications    for    Bridge-stones    (New    York). — Bridge- 
stones  to  be  of  bluestone,  equal  to  the  best  quality  of  North  Eiver 
bluest  one,  free  from  seams  and  imperfections.     Each  stone  to  be 
not  less  than  4  nor  more  than  8   feet  long,  except  in  cases  where 
specially  permitted,  and  2  feet  wide,  and  of  a  uniform  thickness, 
which  may  vary  from  6  to  8  inches,  and  dressed  to  a  fall  on  top 
not  varying  in  evenness  by  more  than  a  quarter  of  an  inch,  and  on 
the  bottom  bedded,  with  sides  square  and  full,  and  ends  cut  to  a 
bevel  of  6  inches  in  2  feet,  and  in  special  cases  to  such  other  bevel 
as  shall  be  directed  by  the  Commissioner  of  Public  Works.     The 
stones  to  be  in  quality  and  workmanship  equal  to  the  pattern  at  the 
office  of  the  Department  of  Public  Works,  and  to  be  cut  so  as  to 
lay  a  joint  not  exceeding  one  fourth  of  one  inch  from  top  to  bot- 
tom on  the  ends  and  one  half  inch  on  the  sides. 

The  bridge-stones  will  be  carefully  inspected  after  they  are 
brought  on  the  line  of  the  work,  and  all  those  which,  in  quality 
and  dimensions,  do  not  conform  strictly  to  these  specifications  shall 
be  rejected  and  must  be  immediately  removed  from  the  line  of  the 
work. 

832.  Relaying   Bridge-stones. — The  bridge-stones  now  on  the 
street  shall  be  relaid  without  extra  charge  therefor.     If  any  are 
found  defective,  new  stone  shall  be  furnished  therefor  at  the  ex- 
pense of  the  contractor.     The  stones  so  furnished  must  correspond 
in  quality,  dimensions,  and  workmanship  to  the  pattern  at  the  office 
of  the  Department  of  Public  Works. 


576 


HIGHWAY   CONSTRUCTION. 


833.  Prices. — The  prices  of  the  materials  employed  for  footway 
pavements  fluctuate  widely,  not  only  in  different  but  in  the  same 
localities;  therefore  the  following  prices  simply  exhibit  the  extreme 
range : 

Cents. 

Bluestone  flagging  3"  thick,  per  square  foot 35  to    95 

Granite  stone  flagging  6"  thick,"per  square  foot 40  "110 

Cement  concrete                                "          "        12  "    20 

Artificial  stone                                 "          "       18$  "    30 

Brick                                                  "          " 9  "     22| 

Granite,  straight,  per  linear  foot 85  "125 

circular,        "        "        100  "137 

Bluestone  curb,  straight,  per  linear  foot 35  "    91 

"      circular        "        "       45  "110 

Sandstone  curb,  straight,       "        "       35  "    75 

"      circular,       "        "       60  "100 

Brick  gutters,  per  square  foot 20  "     38 

Granite     "             "          "       40  "    50     "* 

Granite  bridge-stone  per  linear  foot 70  "  234 

Bluestone        "               "         "       60  "  115 


CHAPTEK  XVIII. 
RECONSTRUCTION  AND  IMPROVEMENT  OF   COUNTRY  ROADS. 

834.  THE  improvement  of  existing  roads  may  be  divided  into 
three  branches: 

(1)  Rectification  of  alignment  and  grades. 

(2)  Drainage. 

(3)  Improvement  of  the  surface. 

The  first  of  these  consists  in  the  application  of  the  princi- 
ples which  have  been  laid  down  for  the  location,  etc.,  of  new  roads, 
and  will  include  straightening  the  course  by  extinguishing  un- 
necessary curves  and  bends;  improving  the  grade  by  either  avoid- 
ing or  cutting  down  hills  and  embanking  valleys;  increasing  the 
width  where  requisite,  and  rendering  it  uniform  throughout. 

The  second  consists  in  applying  the  principles  laid  down  for 
the  drainage  of  new  roads,  and  in  constructing  the  works  necessary 
to  give  them  effect. 

The  third  consists  in  improving  the  surface  in  the  best  possible 
manner,  either  by  the  forming  of  an  artificial  pavement  or,  if  suffi- 
cient funds  for  this  purpose  are  not  available,  by  adopting  such 
local  materials  as  will  make  a  comparatively  fair  surface. 

835.  Improving  Clay  Eoads. — Clay  soils  can  only  be  made  into 
fair  wheelways  by  means  of  thorough  drainage  effected  by  any  of 
the  methods  described  in  Chapter  XIV. 

The  narrower  the  roadway  the  more  effective  will  be  the  drain- 
age. 

If  sand,  gravel,  ashes,  coal-dust,  furnace-slag,  or  shells  can  be 
obtained,  a  coating  of  any  one  of  them,  4  inches  thick,  well  com- 
pacted by  rolling,  will  form  an  improvement;  if  none  of  these 
materials  can  be  obtained,  the  clay  itself  may  be  utilized  by  being 
first  burned,  then  spread  and  rolled. 

577 


578  HIGHWAY    CONSTRUCTION. 

The  manner  of  preparing  and  using  the  clay  is  as  follows :  In 
summer  weather,  or  during  the  hot  season,  the  soil  in  the  proposed 
road  should  be  cut  out  to  a  depth  of  two  feet  into  large  spits  and 
laid  roughly  one  upon  the  other,  and  left  in  that  condition  for 
about  ten  days.  By  this  time  the  sun's  rays  will  have  evaporated 
the  moisture  held  by  soils  of  this  nature.  So  soon  as  the  spits  are 
dry  they  are  submitted  to  the  action  of  fire  in  the  following 
manner :  A  circle  is  formed  fifteen  feet  in  diameter,  surrounded  by 
a  wall  made  of  the  roughest  and  largest  spits,  two  feet  high.  In 
the  inclosure  thus  formed  straw  or  other  light  combustible  ma- 
terial is  laid;  fagots  or  small  pieces  of  wood  are  placed  on  these, 
and  over  them  are  placed  other  spits,  so  as  to  form  a  cone  or 
pyramid,  the  whole  structure  to  be  about  8  feet  high.  Fire  is  then 
applied  to  several  parts  at  once,  due  care  being  taken  to  see  that 
the  spits  sink  evenly  until  the  whole  mass  is  well  alight.  After 
being  well  banked  the  mass  is  left  for  a  day  or  two,  and  as  soon  as 
it  attains  a  good  red  appearance  is  drawn  down,  the  wall  broken, 
the  spits  are  thrown  on  top,  and  others  added  as  required  from 
day  to  day,  until  all  the  earth  dug  has  been  submitted  to  the  same 
process.  In  a  length  of  100  yards  of  road  20  feet  wide  thus  served, 
it  would  take  about  six  fires  to  burn  the  12,000  cubic  feet  contained 
therein.  The  cost  of  labor  would  probably  be  twenty  or  twenty- 
five  cents  per  cubic  yard.  The  burnt  earth  is  then,  after  cooling, 
relaid  upon  the  road,  and  now,  being  of  a  thoroughly  porous 
nature,  settles  into  a  good,  dry,  solid  layer. 

Before  applying  any  of  the  above-mentioned  materials  to  a  clay 
surface  all  mud  and  perishable  material  must  be  removed.  In 
fact,  all  the  weather-worn  clay  should  be  removed  to  a  depth  of 
18  inches  or  more,  and  the  surface  thus  exposed  thoroughly  con- 
solidated by  rolling. 

836.  In  the  maintenance  of  clay  roads  neither  sods  nor  turf 
should  be  used  to  fill  holes  or  ruts;  for,  though  at  first  deceptively 
tough,  they  soon  decay  and  form  the  softest  mud.  Neither  should 
the  ruts  be  filled  with  field-stones :  they  will  not  wear  uniformly 
with  the  rest  of  the  road,  but  will  produce  hard  ridges. 

Trees  and  close  hedges  should  not  be  allowed  within  200  feet 
of  a  clay  road.  It  requires  all  the  sun  and  wind  possible  to  keep 
its  surface  in  a  dry  and  hard  condition. 


RECONSTRUCTION   AND    IMPROVEMENT   OF   COUNTRY   ROADS.   579 

837.  Sand  Roads. — The  aim  in  the  improvement  of  sand  roads 
is  to  have  the  wheelway  as  narrow  and  well-defined  as  possible,  so 
as  to  have  all  the  vehicles  run  in  the  same  track.     An  abundant 
growth  of  vegetation  should  be  encouraged  on  each  side  of  the 
wheelway,  for  by  this  means  the  shearing  of  the  sand  is  in  a  great 
measure  avoided.     Ditching  beyond  a  slight  depth  to  carry  away 
the  rain-water  is  not  desirable,  for  it  tends  to  hasten  the  drying  of 
the  sands,  which  is  to  be  avoided.     Where  possible  the  roads  should 
be  overhung  with  trees,  the  leaves  and  twigs  of  which  catching  on 
the  wheelway  will  serve  still  further  to  diminish  the  effect  of  the 
wheels  in  moving  the  sands  about.     If  clay  can  be  obtained,  a 
coating  6  inches  thick  will  be  found  a  most  effective  and  economi- 
cal improvement.     A  coating  of  4  inches  of  loose  straw  will  in  a 
few  days'  travel  grind  into  the  sand  and  become  as  hard  and  firm 
as  a  dry  clay  road. 

838.  The   maintaining  of  smooth  surfaces  on  all   classes  of 
earth  roads  will  be  greatly  assisted  and  cheapened  by  the  frequent 
use  of  a  roller  (either  steam  or  horse)  and  any  one  of  the  various 
forms  of  road  grading  and  scraping  machines.     In  repairing  an 
earth  road  the  plough  should  not  be  used.     It  breaks  up  the  surface 
which  has  been  compacted  by  time  and  travel. 

839.  Improper  Use   of  Scraping-machines. — The  scraping-ma- 
chine should  not  be  employed  to  drag  the  soft  mud  out  of  the 
ditches  and  place  it  in  the  centre  of  the  road.     The  use  of  the 
scraper  is  to  remove  from  the  road-surface  the  weather  and  traffic- 
worn  material  which  no  longer  possesses  coherence,  and  which,  no- 
matter  how  well  rounded  up  and  rolled,  will  be  converted  into 
mud  after  the  first  shower  of  rain.     This  material,  along  with  that 
removed  from  the  side  ditches,  must  be  deposited  in  such  places 
where  it  cannot  be  washed  back  on  the  road-surface.     As  it  con- 
sists chiefly  of  alluvial  and  vegetable  matter  mixed  with  animal 
excreta,  it  is  useful  for  fertilizing  purposes  and  may  be  disposed  of 
to  the  neighboring  farmers ;  but  it  must  not  be  left  in  heaps  on  the 
roadside,  to  be  removed  by  them  at  their  leisure. 

840.  Cost  of  Constructing  Earth  Roads. — The  following  prices 
are  taken  from  the  bids  received  for  the  construction  of  wagon- 
roads  through  the  Yellowstone  National  Park.     The  specifications 
were :  clearing,  30  feet  wide ;  roadway,  18  feet  wide  and  6  inches 
higher  at  the  middle  than  the  edges ;  on  each  side  a  berme  of  1 


580  HIGHWAY   CONSTRUCTION. 

foot,  with  a  ditch  on  the  outer  side  5  feet  wide  at  top,  2  feet  at 
bottom,  and  18  inches  deep.  The  roadway  to  be  covered  with  9 
inches  of  clay  or  earth. 

PEICE   PEE  MILE. 

Highest,  $4382.  Lowest,  $2529. 

841.  Cost  of  maintaining  earth  roads  ranges  from  $50  to  $80 
per  annum  per  mile. 

842.  Value   of  Improvements. — The   improvement  of  roads  is 
chiefly  an  economical  question  relating  to  the  waste  of  effort  and 
the  saving  of  expenditure.     Good  roads  reduce  the  resistance  to 
locomotion,  and  this  means  reduction  of  the  effort  required  to 
move  a  given    load.     Any    effort   costs    something,  and  so   the 
smallest  effort  costs  the  least,  and  therefore  the  smoothest  road 
saves  the  most  money  to  every  man  who  traverses  it  with  a  vehicle. 

843.  Before  undertaking  any  improvement  it  is  generally  re- 
quired  to   know  the  cost  of  the  proposed  improvement  and  the 
benefits  it  will  produce.     In  the  improvement  of  roads  the  amount 
of  money  that  may  be  profitably  expended  for  any  proposed  im- 
provement may  be  calculated  with  sufficient  accuracy  as  follows. 
First  obtain  the  following  data: 

(1)  The  quantity  and  quality  of  the  traffic  using  the  road. 

(2)  The  cost  of  haulage. 

(3)  Plan  and  profile  of  the  road. 

(4)  Character  and  cost  of  the  proposed  improvement. 

844.  From  the  data  so   obtained  ascertain   the  total  annual 
traffic  and  the  total  annual  cost  of  hauling  it.     Next,  calculate  the 
annual  cost  of  hauling  the  given  tonnage  over  the  improved  road, 
which  may  be  obtained  from  the  data  given  in  Chapter  X.     Then 
the   difference   between  the  two  costs  will  represent  the  annual 
interest  on  the  sum  that  may  be  expended  in  making  the  improve- 
ment.    For  example,  if  the  annual  cost  of  haulage  over  the  given 
road  is  $10,000  and  the  cost  for  hauling  the  same  over  the  im- 
proved road  will  be  $7000,  the  difference,  $3000,  with  money  at  §% 
per  annum,  represents  the  sum  of  $50,000  that  may  be  expended  in 
carrying  out  the  improvement. 

845.  For  the  purpose  of  ascertaining  the  amount  of  money  that 
may  be    profitably   expended    in   improvements,  each   part  of   a 
given   road   must   be   separately   investigated   as   above   directed, 


RECONSTRUCTION   AND   IMPROVEMENT   OF   COUNTRY   ROADS.    581 

because  the  amount  that  may  be  expended  varies  with  the  amount 
of  traffic;  and  as  the  quantity  of  traffic  using  different  portions  of 
a  road  varies,  the  data  obtained  close  to  a  town  cannot  be  taken  as 
correct  for  distant  portions,  nor  the  data  obtained  for  distant  por- 
tions as  correct  for  portions  close  to  towns. 

846.  The  defects  of  existing  roads  may  be  stated  as  follows : 

(1)  -Unnecessary  ascents  and  descents. 

(2)  Unnecessary  length. 

(3)  Imperfect  surface. 

The  money  benefit  accruing  from  the  elimination  of  any  one 
or  all  of  these  defects  may  be  approximately  calculated  as  follows : 

847.  Profit    of  Eliminating   Grades. — Take    for    example    the 
elimination  of  a  5$  grade  1  mile  long  from  an  earth-road.     The 
observations  on  this  grade  show  that  the  daily  traffic  over  it  is  224 
teams,  each  dragging  an  average  load  of  800  pounds,  equivalent  to 
24,000  tons  per  annum;  that  the  time  occupied  in  traversing  it 
is  half  an  hour;  that  the  value  of  a  team's  labor  is  30  cents  per 
hour.     Therefore  the  cost  of  haulage  on  this  grade  is  33T^  cents 
per  ton-mile,  or  $8064  per  annum  for  the  total  tonnage  using  it. 

From  an  examination  of  the  ground  we  find  that  the  grade  can 
be  reduced  to  2$  by  constructing  a  new  piece  of  road  2  miles  long, 
and  that  the  cost  of  the  change  will  be  $18,000. 

From  the  resistance  to  traction  opposed  by  the  new  road-surface 
plus  the  effect  of  gravity  we  find  that  a  team  will  haul  a  load,  on 
the  reduced  grade,  of  1200  pounds,  and  that  the  time  occupied  in 
travelling  the  two  miles  will  be  one  hour.  Therefore  the  cost  per 
ton-mile  will  be  28  cents,  or  $6720  per  annum  for  the  total  tonnage. 
To  this  add  the  annual  cost  of  maintaining  the  extra  mile  of  new 
road,  say  $200;  this  gives  $6920  as  the  cost  per  annum,  which 
subtracted  from  the  original  cost  of  $8064  leaves  $1144;  which  sum, 
with  money  at  6#,  represents  a  capital  of  $19,066,  a  sum  sufficient 
to  make  the  proposed  change. 

848.  The  money  loss  caused  by  grades  may  be  approximately 
ascertained  as  follows :  Ascertain  the  cost  of  hauling  a  ton  on  level 
portions  of  the  same  road  and  on  the  grade;  take  the  difference 
and  multiply  it  by  the  annual  tonnage :  the  product  represents  the 
annual  loss.     For  example,  the  cost  per  ton-mile  on  a  level  is  22.50 
cents,  on  a  5$  grade  33.60  cents;  difference  11.10  cents  =  loss  per 
ton,  or  an  annual  loss  on  a  traffic  of  30,000  tons  of  $3330,  which  is 


582  HIGHWAY   COKSTKUCTIOK. 

the  interest  at  6$  on  $55,000;  which  sum  the  community  could 
borrow  for  the  purpose  of  reducing  the  grade  to  a  level,  pay  the 
interest  and  be  no  worse  off  financially,  and  have  a  good  road 
besides. 

849.  Profit  of  Decreasing  Length. — The  Profit  arising  from 
the  elimination  of  any  unnecessary  length  maybe  stated  as  follows: 

(1)  Saving  in  time. 

(2)  Reduction  in  wear  and  tear  of  horses  and  equipment. 

(3)  Saving  the  cost  of  maintenance  of  such  unnecessary  portion. 

(4)  Reduction  in  the  cost  per  ton-mile  of  haulage. 

(5)  Saving  by  the  return  of  the  land  previously  occupied  by 
the  road  to  other  and  perhaps  more  remunerative  uses. 

(6)  The  decrease  in  the  working  time  of  the  horses  will  permit 
of  a  slight  increase  in  the  load. 

The  saving  in  the  above  items  will  vary  directly  as  the  distance 
saved. 

As  an  example  take  a  level  road  5  miles  long  and,  neglecting 
the  saving  in  time  and  rental  value  of  the  land  saved,  and  increase 
of  load,  what  will  be  the  effect  of  decreasing  its  length  one  mile  ? 

(1)  Saving  of  the  annual  maintenance  of  1  mile. 

(2)  Reduction  of  the  time  required  in  travelling  over  the  road, 
thus  permitting  persons  who  make  several  daily  trips  to  make  an 
extra  trip  per  day  at  the  same  cost  for  driver  and  horse-feed  and 
with  no  extra  fatigue  to  the  horses. 

(3)  Saving  in  wear  and  tear  of  horses  shoes,   harness,   and 
vehicles. 

(4)  Saving  in  the  ton-mile  cost  for  haulage. 

Assuming  observation  of  the  traffic  to  show  that  100  teams 
drawing  average  net  loads  of  2500  pounds  use  the  road  daily,  and 
that  the  cost  per  ton-mile  is  20  cents,  therefore  the  annual  tonnage 
=  33,480  tons,  and  the  total  annual  cost  of  haulage  per  ton-mile 
=  $6696. 

Slimming  up  the  items,  we  have : 

Saving  of  maintenance  1  mile $50.00 

33,480  ton-miles,  at  20  cents $6696.00 

6746.00 

Which  is  equivalent  to  the  interest  at  6$  on  $112,433,  which  sum 
could  be  borrowed  to  make  the  improvement. 


RECONSTRUCTION    AND    IMPROVEMENT    OF    COUNTRY    ROADS.    583 

850.  Profit  of  Improving  the  Surface. — The  benefits  accruing 
from  this  improvement  are  a  general  reduction  in  the  cost  of 
haulage  and  wear  and  tear.  The  smooth,  hard  road-surface 
enables  the  same  power  to  haul  a  greater  load  with  the  same  and 
even  less  fatigue  than  it  can  on  a  rough  surface. 

The  less  the  resistance  to  traction  the  greater  the  load,  and  the 
greater  the  load  the  sooner  will  the  produce  be  marketed.  Besides 
the  wear  and  tear  on  a  smooth  surface  is  not  one  third  tjiat  on  a 
rough  surface. 

Assuming  that  it  is  required  to  know  how  much  may  be  profit- 
ably expended  in  improving  the  surface  of  a  level  earth  road  one 
mile  long,  and  that  the  observations  show  that  it  is  used  by  50 
teams  per  day,  each  dragging  when  the  road  is  in  good  condition  a 
net  load  of  one  ton,  and  when  in  bad  condition  a  net  load  of  1200 
pounds,  and  that  the  cost  per  ton- mile  when  the  road  is  in  good 
condition  is  18  cents,  and  when  in  bad  condition  39  cents;  that  the 
road  is  in  good  condition  for  one  half  the  year,  and  in  bad  condition 
for  the  other  half;  that  the  cost  of  paving  and  improving  the 
road  will  be  $7500  per  mile, — then  we  have : 

150  days,  at  50  tons  =    7500  tons,  at  18  cents =  $1350.00 

150     "       "27     "    =    4050    "     "  39      "    .  ..=     1579.50 


11,550    " 
Cost  of  maintaining  the  earth  road 50.00 

$2979.50 
/ 

$2979.50  -4-  11,550  =  25.81  cents,  average  cost  per  ton-mile  for 
haulage. 

On  a  broken-stone  road  in  its  average  condition  and  at  all 
times  throughout  the  year  a  team  of  horses  will  draw  a  net  load  of 
3  tons  at  a  speed  of  3  miles  per  hour.  If  the  cost  of  horses'  labor, 
•drivers'  time,  etc.,  be  taken  at  30  cents  per  hour,  the  cost  per  ton- 
mile  will  be  10  cents,  or  for  the  11,550  tons  annual  traffic  $1155; 
to  which  add  for  annual  maintenance  of  one  mile  of  road  $350. 
The  annual  cost  will  therefore  be  $1605,  which  deducted  from  the 
former  cost  of  $2979.50  leaves  $1375,  which,  with  money  at  §% 
is  equivalent  to  the  annual  interest  on  $22,916,  which  sum  may 
be  expended  in  improving  the  road-surface  one  mile  long. 

The  annual  loss  occasioned  by  the  waste  of  motive  power  on 


584 


HIGHWAY   CONSTRUCTION. 


unimproved  road-surface  is  clearly  shown  by  the  above  calculations. 
In  the  best  condition  of  the  earth  road  it  required  50  teams  to  move- 
50  tons;  on  the  improved  surface  but  17  teams  are  required  to  per- 
form a  like  work,  and  the  labor  of  the  teams  formerly  required 
may  be  more  profitably  employed  at  other  work.  On  the  earth 
road  in  its  worst  condition  it  required  two  teams  to  move  one 
ton;  on  the  improved  surface  but  one  team  is  required  to  move 
three  tons. 

851.  Any  calculations  made  to  ascertain  the  benefits  accruing  to 
a  community  from  improved  roads  must  necessarily  fall  far  short 
of  the  truth,  since  no  account  can  be  taken  of  the  saving  in  wear 
and  tear  of  horses  and  vehicles,  of  the  saving  in  time  caused 
by  the  increased  size  of  the  loads,  which  thus  decrease  the  number 
of  days  on  which  hauling  must  be  done,  thus  allowing  the  time  to  be 
more  profitably  employed,  or  of  the  enhancement  of  the  value  of 
the  land  in  consequence  of  the  improved  roads,  or  of  the  social 
advantages  arising  from  their  improvement. 


CHAPTER  XIX. 
MAINTENANCE.— REPAIRING  ;  CLEANSING  ;  WATERING. 

852.  Maintenance. — The    maintenance    of  a    roadway   is    the 
keeping  of  it,  as  nearly  as  practicable,  in  the  same  condition  as  it 
was  when  originally  made;    the  repair  of  a  roadway  is  the  work 
rendered  necessary  to  bring  it  up  to  its  original  condition  after  it 
has  become  deteriorated  by  neglect  to  maintain  it.   Thus  there  is  a 
wide  distinction  between  the  two  operations,  and  when  the  com- 
parison  of    costs   is  instituted    errors  are   frequently  caused  by 
setting  the  repairs  of   one  r6*ad   against  the   maintenance  of  an- 
other or  vice  versa. 

853.  Necessity  for  Maintenance. — No  matter  how  well  made  a 
structure  may  be,  or  how  carefully  the  materials  used  have  been 
inspected,  the  use  of  it  will  exhibit  defects  which  it  is  almost  im- 
possible to  guard  against,  such  as  variableness  in  the  quality  of 
the  material  and  slighting  on  the  part  of  the  workmen.    Moreover, 
every  material,  whether  natural  or  artificial,  is  continually  under- 
going a  process  of  deterioration  by  the  action  of  the  elements;  this 
decay  is  hastened  or  retarded  in  proportion  to  the  means  employed 
and  care  bestowed  to  arrest  it.     The  materials  employed  for  pave- 
ments are    not  only  subjected  to    the  destroying   action  of  the 
elements,  but  also  to  abrasion  and  concussion,  which  by  themselves 
are  powerful  destroying  agents.     In  view  of  these  facts  the  con- 
tinual presence  of  workmen  engaged  in  repairing  pavements  must 
not  in  all  cases  be  considered  as  evidence  of  defective  construction  or 
improper  materials,  but  as  an  honest  endeavor  by  those  in  charge  of 
the  highways  to  preserve  the  surface  in  good  travelling  condition. 

854.  The  essential  requisite  to  the  preservation  of  a  good  sur- 
face is  eternal  vigilance  on  the  part  of  the  roadway  keepers.     If  a 
depression  appears  in  consequence  of  settlement,  defective  material, 
or  other  causes,  it  must  be  at  once  eliminated;  if  not,  it  will  be 

585 


5S6  HIGHWAY   CONSTRUCTION. 

quickly  deepened  and  enlarged  by  each  succeeding  vehicle,  and 
will  thus  become  an  obstacle  to  safe  travelling. 

855.  Good  Maintenance  comprises: 

(1)  Constant  daily  attention  to  repair  the  ravages  of  traffic  and 
the  elements.   The  character  and  quantity  of  these  repairs  will  vary 
with  the  character  of  the  pavement  and  the  manner  of  its  construc- 
tion.    With  granite  blocks  laid  on  a  concrete  foundation  they  will 
be  the  least,  with  broken  stone  they  will  be  the  greatest;  the  other 
materials,  as  wood,  asphalt,  and  brick,  lying  between. 

(2)  Cleansing,  i.e.,  removing  the  detritus  caused  by  wear,  horse- 
droppings,  and  other  refuse  finding  its  way  into  the  streets. 

(3)  Watering  to  lay  the  dust. 

856.  Systems  of  Maintenance. — Three  systems  of  maintaining 
pavements  are  in  vogue : 

(1)  By  contract,  at  a  fixed  price  per  square  yard  per  annum  for 
a  fixed  period.     Under  this  method  asphalt  pavements  are  main- 
tained in  both  the  United  States  and  Europe.     Wood  pavements 
are  also  maintained  under  this  system  in  Europe,  but  rarely  in 
America.     The  form  of  contract  under  which  this  system  is  carried 
out  in  Europe  is  given  in  Articles  214  and  265.     The  advantage  of 
this  system  is  that  of  having  some  one  admittedly  responsible  for 
the  condition  of  the  pavement.     Its  defects  are  (a)  the  difficulty  of 
determining  the  exact  condition  the  pavement  is  in  at  the  expira- 
tion of  the  contract,     (b)  It  is  an  extremely  costly  system. 

(2)  By  independent  contracts  for  the  labor  and  materials,  the 
tools  and  supervision  being  furnished  by  the  city. 

(3)  By  men   in  the  employment  of    the  city,  materials,  etc., 
being  purchased  in  the  open  market.     This  is  the  system  adopted 
by  the  city  of  Liverpool,  and  the  excellence  of  that  city's  pavements 
needs  no  comment. 

857.  Maintenance  of  Country  Roads. — When  a  country  high- 
way is  finished  and  thrown  open  to  traffic,  it  cannot  be  left  to  take 
care  of  itself;  if  it  is,  it  will  soon  deteriorate  and  become  bad.    It  is 
to  the  thorough  appreciation  of  this  fact  that  the  excellence  of  the 
European  roads  is  due.     Upon  its  completion  a  system  of  main- 
tenance must  be  instituted.     Three  systems  are  in  vogue :  (a)  By 
contract  with  private  parties,      (b)  Personal  service  by  the  rural 
population,     (c)  By  men  permanently  employed  for  the  purpose 
by  the  community. 


MAINTENANCE.— REPAIRING;   CLEANSING;   WATERING.     587 


(a)  The  contract  system  is  unsatisfactory,  from  the  difficulty 
of  getting  a  proper  observance  of  the  terms  of  the  contract  from 
the  contractor  or  his  employers. 

In  Austria  during  the  last  century  experiments  were  made  with 
the  letting  of  the  maintenance  of  the  state  roads  to  private  parties, 
which  experiments  proving  unsatisfactory,  caused  the  government 
to  take  the  work  in  hand,  and  it  has  adhered  to  this  practice  up  to 
the  present  day,  with  a  short  interruption  in  the  years  1858-1861, 
during  which  time  the  keeping  of  the  roads  was  again  let  by  con- 
tract, and  again  gave  unsatisfactory  results. 

(b)  The  personal-service  or  labor-tax  system  is  not  applicable  to 
the  maintenance  of  improved  roads.     In  fact,  it  is  not  applicable  to 
any  class  of  roads;  it  is  unsound  in  principle,  unjust  in  its  opera- 
tion, wasteful  in  its  practice,  and  unsatisfactory  in  its  results. 

(c)  By  men  permanently  employed  for  the  purpose  by  the  com- 
munity.    This  system  has  been  adopted  by  France,  Germany,  and 
nearly  all  European  countries.     Its  advantages  are  many.     The 
men  so  employed  become  familiar  with  the  peculiarities  of  their 
sections  and  with  the  best  way  to  deal  with  them,  and  good  men 
soon  learn  to  take  an  interest  in  the  road  which  it  is  their  business 
to  keep  in  order.     "  It  is  in  vain  to  expect  the  same  skill  or  in- 
dustry from  men  employed  by  the  job,  or  having  no  interest  in  the 
goodness  of  the  road,  or  in  making  the  most  of  the  means  at  their 
disposal." 

858.  The  maintenance  or  keeping  of  the  road  in  proper  order 
consists  of: 

(1)  The  daily  removal  of  the  detritus  either  in  the  form  of  dust 
or  mud,  the  horse-droppings  and  other  rubbish. 

(2)  The  filling  of  ruts  or  depressions. 

(3)  The  cleansing  out  of  the  ditches,  catch-basins,  and  water- 
courses. 

(4)  Watering  the  surface  in  dry  weather. 

The  disintegrating  action  of  the  weather  and  the  friction  of  the 
traffic  produces  dust;  this  dust  renders  the  road  heavy  for  traffic 
and  annoys  passengers  and  horses.  If  rain  falls,  the  dust  is  con- 
verted into  mud.  A  well-swept  road  produces  no  mud  after  a  rain, 
at  least  not  for  several  days.  However,  if  the  humidity  continues, 
the  road-surface  becomes  at  first  sticky  and  finally  is  covered  with 
mud.  Mud  makes  the  tracks  of  wheels  apparent ;  other  vehicles 


588  HIGHWAY    CONSTRUCTION. 

follow  in  them,  and  after  a  while  ruts  are  formed  which  injure 
the  road.  Thus  it  is  essential  that  the  dust  and  mud  be  removed 
from  the  road-surface.  The  dust  may  be  removed  by  sweeping, 
the  mud  by  scraping.  These  sweepings  and  scrapings  should  not 
be  left  on  the  sides  of  the  road  to  be  redistributed  by  the  first 
wind,  but  should  be  immediately  removed :  they  might  be  utilized 
by  the  farmers  as  an  adjunct  to  their  manure-pile. 

(1)  The  best  time  for  sweeping  is  early  in  the  morning  before 
the  dew  has  dried ;  besides,  there  is  less  inconvenience  to  the  traffic 
at  that  time. 

The  removal  of  dust  and  mud  may  be  effected  either  by  brooms, 
and  hand-scrapers  or  by  mechanical  sweepers  and  scrapers  drawn 
by  horses.  In  the  rural  districts  the  former  will  be  most  suitable,, 
while  in  the  vicinity  of  towns  the  latter  will  be  most  economical. 

(2)  Daily  attention  must  be  given  to  the  making  of  slight 
repairs  such  as  filling  ruts  and  depressions;  for,  however  well  the 
materials  may  be  laid  and  rolled,  the  traffic  will  search  out  the 
places  which  are  weak  or  have  escaped  the  full  pressure  of  the 
roller. 

(a)  All  ruts  should  be  at  once  filled.     If  there  are  three  parallel, 
the  centre  rut  should  be  first  filled.     The  traffic  is  thus  slightly 
diverted,  as  a  horse  will  avoid  new  metal. 

(b)  Depressions  or  hollows  should  be  filled  at  once.     The  sur- 
face of  the  road  should  never  be  allowed  to  lose  its  regular  section, 

(c)  If  the  surface  of  the  road  where  these  patches  are  to  be 
placed  is  very  hard,  it  must  be  loosened  up  with  the  pick. 

(d)  Water  lodging  in  a  depression  should  not  be  let  off  by 
digging  a  trench  with  the  pick-axe  to  the  side  of  the  roadway.     The 
depression  should  be  filled  up. 

(e)  All  loose  stones  should  be  picked  off  at  once  and  stored  for 
use  in  filling  hollows.     If  allowed  to  remain,  they  are  not  only  dan- 
gerous to  horses,  but  are  liable  to  be  crushed  or  to  be  forced  through 
the  skin  of  the  roadway,  thus  causing  damage. 

(3)  At  all  seasons  of  the  year  the  gutters  should  be  kept  free 
from  mud  and  rubbish  of  all  sorts,  and  anything  that  impedes  the 
free  discharge  of  the  rain-water  from  the  road  must  be  removed. 

The  ditches  and  culverts  should  be  well  cleaned  out  in  advance 
of  the  spring  and  fall  rains.  In  northern  localities,  where  snow 
lies  for  some  time,  the  outlets  of  all  ditches  and  culverts  should  be 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       589 

opened  and  cleaned  out  before  the  spring  thaw  sets  in.  In  the  fall 
all  weeds  and  grass  in  the  ditches  should  be  cut,  and  the  culverts 
.and  water-outlets  left  in  good  shape  for  the  winter. 

All  bridges  should  be  examined  at  least  twice  a  year. 

All  structures  such  as  bridges,  culverts,  and  drains  should  be 
numbered,  the  numbers  being  legibly  painted  on  some  prominent 
part;  and  a  book  should  be  kept  in  which  the  dates  and  condition 
•at  periodical  inspections  are  entered. 

Retaining-walls  should  be  examined  and  repaired  at  least  once  a 
year. 

Guard-stones  should  be  reset  immediately  they  become  displaced. 

Parapets,  mile-stones,  and  guide-posts  should  be  periodically 
examined,  repaired,  and  reset. 

(4)  Watering  to  lay  the  dust  is  essential  in  summer  and  occa- 
sionally in  winter.  In  summer,  during  the  dry  hot  weather,  the 
road-surface  becomes  extremely  brittle  and  then  should  be  watered, 
the  dust  and  refuse  having  been  first  removed. 

Sometimes,  in  winter  especially,  after  frost  the  road  gets  very 
sticky  and  picks  up  freely  under  passing  wheels.  It  should  then 
also  be  watered  and  all  slush  and  mud  removed.  When  the  dust 
is  regularly  removed  from  a  road  it  does  not  require  so  much 
watering  in  dry  weather  as  it  otherwise  would. 

A  road  should  never  be  watered  unless  it  really  needs  it,  as  too 
much  water  is  injurious  and  it  increases  the  wear  from  traffic. 

The  most  common  method  of  watering  a  road  is  that  of  carrying 
the  water  in  barrels  mounted  on  wheels  or  vehicles  specially  con- 
structed for  the  purpose  and  distributing  it  therefrom  through  a 
perforated  pipe. 

858a.  The  Errors  Commonly  Committed  in  the  Maintenance  of 
Broken-stone  Roads  are: 

(1)  The  Unskilful  Application  of  Materials. — This  means  using 
more  material  than  is  legitimately  required,  and  the  applying  it 
in  an  improper  manner.  Roads  always  wear  out  in  a  succession 
of  small  round  holes  or  long  straight  lines.  The  usual  unskilful 
method  of  repair  is  to  put  a  square  patch  on  a  round  hole.  This 
means  that  at  least  a  third  too  much  material  is  used,  with  a 
bumpy  or  uneven  surface  as  the  result;  or  the  long  lines  are  filled 
tip  too  full,  and  the  overplus  means  so  much  stone  wasted.  In 


590  HIGHWAY    CONSTRUCTION. 

coating  a  large  surface  it  is  the  aim  of  an  unskilful  roadman  to. 
spread  all  the  stone  he  can,  "to  make  a  good  show."  The  result 
is  the  material  is  heaped  on,  often  three  stones  thick,  or  else  scat- 
tered about  as  if  sprinkled  on  the  surface.  Material  thus  improp- 
erly placed  will  not  be  consolidated  in  the  position  it  was  origi- 
nally intended  for;  it  will  be  rolled  about  by  each  passing  vehicle; 
it  thus  loses  its  size,  its  shape,  its  angles  (so  necessary  for  proper 
consolidation),  and  annoys  every  one  using  the  road.  The  material 
so  wasted  makes  the  cost  of  maintenance  15  to  20  per  cent  greater 
than  is  necessary.  The  misapplication  of  the  material  also  produces 
an  extremely  uneven  contour,  which  necessitates  a  great  amount 
of  new  material  being  again  applied  later  to  remedy  the  uneven- 
ness  that  could  be  easily  obviated  if  the  material  at  first  had  been 
properly  applied. 

No  material  should  be  placed  on  the  road-surface  until  the 
latter  is  properly  prepared  to  receive  it.  If  ruts  have  formed,  only 
just  sufficient  stone  should  be  used  to  fill  the  ruts  to  the  level  of 
the  adjoining  road-surface  (it  is  far  better  to  underfill  a  rut  than 
overfill  it).  Material  can  always  be  added  without  much  expense, 
but  ruts  filled  too  full  not  only  cause  needless  inconvenience,  but 
material  is  used  wrongfully,  and  becomes  absorbed  where  it  is  not 
required,  adding  a  large  expense.  If  the  road  is  regularly  coated 
and  maintained,  there  is  no  reason  why  ruts  should  form.  If  the 
manual  labor  is  efficient,  no  ruts  will  form — if  directly  a  road  is 
tracking,  which  is  the  real  preliminary  for  ruts,  steps  are  taken  to 
turn  the  traffic.  This  is  easily  done  if  the  surface  is  kept  clean  and 
free  from  detritus.  When  a  road  shows  signs  of  wearing  out  small 
holes  successively  appear,  and  these  should  at  once  be  attended  to. 
The  correct  process  is  to  open  the  edge  of  these  wearing  holes 
about  3  inches  over  the  exact  edge  by  picking  up  the  road -surf  ace 
with  a  sharp  pickaxe,  then  fill  with  fine  stone  run  out  to  a  thin 
V-point,  and  cover  with  sharp  sand  or  road- scrapings.  In  dry 
weather  the  materials  should  be  moistened  with  water. 

In  coating  large  surfaces  the  material  should  not  be  applied 
more  than  two  stones  thick  at  one  time;  otherwise  the  bottom 
layer  will  not  be  consolidated,  the  top  layer  will  be,  and  when  a 
secondary  settling  takes  place  this  will  collapse  and  an  uneven 
surface  will  result.  In  patching  or  coating  a  hill  it  is  practically 


MAINTENANCE. — REPAIRING  ;   CLEANSING  ;   WATERING.        591 

impossible  to  make  a  patch  lie  firm  unless  the  road  is  cross-scored. 
The  extra  labor  for  this  is  but  a  very  minor  expense  compared  with 
the  loss  of  value  of  material  where  it  remains  kicking  about  with- 
out being  consolidated.  AVhere  roads  are  continually  in  ruts,  and 
there  is  no  special  reason  for  such  to  show,  it  will  usually  be  found 
useless  to  attempt  any  remedy  other  than  the  taking  up  of  the 
rutted  portion,  strengthening  the  foundation,  and  relaying  the 
material.  This  seems  expensive,  but  it  will  be  found  to  be  the 
most  economical,  and  a  lastingly  good  road  will  result. 

(2)  Use   of  Improper   Materials. — Well-made  roads    are    fre- 
quently ruined  by  the  use  of  local  materials  whose  first  cost  is 
cheap,  but  excessively  dear  in  the  end,  by  want  of  substance  and 
unsuitability  for  the  purpose  required. 

(3)  Neglect  of  Repairs. — By   neglecting  to  make  repairs  and 
restore   worn-out   material   the   road   becomes  so  "thin"  that  it 
collapses  under  the  traffic.     The  neglect  of  applying  new  material 
is  termed  "  starving  "  the  road.   The  remedy  is  a  most  expensive  one, 
for  the  whole  of  the  "starving"  has  to   be  made   good  at   once, 
instead  of  being  spread  out  in  proper  maintenance  over  a  period  of 
years. 

(4)  Insufficient  and  Unskilful  Manual  Labor. — Manual  labor 
must  of  necessity  be  employed  for  caring  for  the  road,  and  upon 
its  efficiency  and  skill  will  depend  the  condition  of  the  road.    This, 
being    the   easiest   portion   of   road   maintenance   to   abolish  for 
"  saving,"  and  the  most  constant  source  of  apparent  expenditure, 
is   generally  the  first  to  suffer  when  "economy"  takes  the  place 
of   efficient  and   economical   management ;  but  there  is  no  more 
wasteful  system,  leading  to  bad  roads,  than  thus  starving  roads. 
Manual  labor  should  be  arranged  so  as  to  allow  each  workman  to 
be    properly   instructed  and   superintended.      Without    this,  the 
manual-labor  difficulty  will  be  found  to   be   one   long  series   of 
annoyance  and  disappointment.     Until  a  workman  thoroughly  ap- 
preciates that  he  is  responsible  fora  GOOD  road,  and  not  responsible 
for  making  a  "show,"  he  is  no  good  as  a  roadman.    "  Here's  a  hole, 
put  a  shovelful  of  stones  into  it,"  is  not  road-repairing. 

The  ever-changing  "system"  of  management  invariably  results 
in  bad  roads.  No  roads  can  be  effectually  maintained  where  the 
head  or  personnel  is  constantly  changing.  Each  change  usually  has 


592  HIGHWAY   CONSTRUCTION. 

the  same  unsatisfactory  ending;  the  roads  will  be  surfeited  with 
material,  more  often  bad  because  it  is  cheap,  or  else  starved  of 
necessary  material  or  labor  because  the  initial  outlay  is  great  or 
appears  so. 

859.  Amount  of  Water  Required. — Mr.  E.  P.  North  found  the 
amount  of  water  necessary  to  keep  macadam  roads  in  the  vicinity 
of  New  York  from  becoming  dusty  to  be  at  the  rate  of  71.3  cubic 
feet  per  1000  square  yards  applied  twice  in  a  day,  or  say  143  cubic 
feet  per  day.     In  very  hot  or  beeezy  weather  this  was  not  quite 
enough. 

On  the  telford  roads  in  New  York  25  cubic  feet  applied  four 
times  a  day  are  necessary  per  100  square  yards,  or  about  100  cubic 
feet  per  day. 

One  water-cart  holding  79  cubic  feet  waters  35,000  square 
yards  four  times  a  day,  keeping  it  free  from  dust  except  during 
windy  weather. 

860.  Cost  of  Maintenance. — The  cost  of  maintenance  is  very 
variable,  being  principally  dependent  upon  the  degree  of  perfection 
with  which  the  road  has  been  constructed,  but  largely  influenced 
by  the  employment  of  a  sufficient  number  of  skilled  laborers  to 
maintain  the  surface  in  proper  condition  under  skilled  supervision. 

The  cost  of  maintaining  the  roads  of  France  varies  from  $60  to 
$500  per  mile,  with  an  average  of  $150,  of  which  about  half  is  for 
labor  and  half  for  materials. 

The  following  table  gives  the  cost  per  annum  per  square  yard 
for  the  maintenance  of  macadamized  streets  in  different  localities : 

Bristol,  Eng 8  to    24  cents 

Charing  Cross,  London* 100 

Glasgow,  Scotland 17 

Leeds,  Eng 20  to    26 

Liverpool,  Eng 24  "    36 

Manchester,  Eng  12  "    40 

Paris,  France 19  "258 

Toronto,  Can , 24 

Belgium 4  "    10 

Germany 20  "    80 

*  Now  paved. 


MAINTENANCE.— REPAIRING  ;    CLEANSING  ;    WATERING.       593 

The  annual  expenditure  necessary  to  keep  a  given  highway  in 
proper  repair  may  be  ascertained  very  closely  by  combining  the  dif- 
ferent factors  of  cost.  These  factors  are: 

I.  The  average  number  of  cubic  yards  of  stone  per  mile  which 
will  be  necessary  to  keep  the  road  in  proper  repair,  or,  in  other 
words,  the  quantity  of  stone  which  will  be  required  to  replace  the 
annual  wear  caused  by  traffic  and  the  weather,  and  removed  in  the 
form  of  mud  and  dust.  This  quantity  depends  upon  the  following 
subsidiary  factors: 

1.  Width  of  road. 

2.  Nature  of  foundation,  drainage,  and  thickness  of  crust. 

4.  Situation  of  the  road. 

5.  Quality  of  the  stone  to  be  applied. 

One  cubic  yard  of  stone  broken  to  pass  through  a  2-inch  gauge 
will  cover  30  square  yards  of  road,  one  stone  thick,  and  will  give  f 
inch  thickness  of  consolidated  material.  The  quantity  of  material 
required  to  cover  a  mile  of  road  is  evidently  directly  proportional  to 
the  width  of  the  road.  On  a  road  16  feet  wide,  having  a  sufficient 
thickness  of  crust  composed  of  good  sound  stone,  having  a  good 
foundation,  the  road  being  well  drained  and  freely  accessible  to  sun 
and  wind,  the  traffic  being  equal  to  100  tons  per  day — not  of  an  ex- 
traordinary nature,  and  carried  on  broad-tired  wheels — the  wear 
should  be  about  one-eighth  of  an  inch  per  annum.  Such  a  road 
would  require  about  54  cubic  yards  of  good  sound  broken  stone 
per  annum  to  keep  it  in  repair. 

II.  The  cost  of  the  material.  If  this  is  procured  by  contract,  its 
cost  will  be  positive,  but  if  procured  by  day's  labor  under  the 
supervision  of  the  authorities,  its  cost  will  depend  upon  the  follow- 
ing subsidiary  factors: 

1.  Cost  of  quarrying,  including  labor,  supplies,  use  of  tools,  and 
royalty  or  interest  on  cost  of  quarry. 

The  cost  of  quarrying  varies  with  the  nature  of  the  stone  and 
character  of  the  quarry.  An  average  price,  including  all  items  of 
cost,  is  about  60  cents. 

2.  Cost  of  breaking,  including  labor,  supplies,  interest,  and  de- 
preciation of  plant. 

The  cost  of  breaking  varies  with  the  stone  and  ranges  from  30 
to  80  cents  per  cubic  yard. 


594  HIGHWAY   CONSTRUCTION. 

3.  Cost  of  hauling  from  quarry  to  depots  at  the  roadside. 

This  cost  varies  with  the  distance  and  character  of  the 
roads,  and  ranges  between  20  and  50  cents  per  cubic  yard  per 
mile. 

4.  Cost  of  stacking  at  the  roadside. 

This  may  be  taken  at  5  cents  per  cubic  yard. 

5.  Cost  of  loosening  the  stones  in  the  heaps  (a  considerable 
item  in  frosty  weather  or  when  the  stones  have  lain  for  some 
time). 

6.  Cost  of  hauling  stones  from  depots  to  the  portion  of  the  road 
where  they  are  to  be  used. 

7.  Cost  of  preparing  the  road-surface  to  receive  the  stone. 

8.  Cost  of  spreading  the  stone. 

The  combined  cost  of  the  items  5,  6,  7,  and  8  varies  between  20 
and  50  cents  per  cubic  yard.  As  it  consists  of  manual  labor  performed 
by  the  same  men  it  is  difficult  to  affix  a  specific  value  to  each 
item. 

III.  The  cost  of  compacting  the  stone.     This  item  is  very  vari- 
able; it  includes  the  wages  of  roller  attendants,  two  sweepers,  team 
labor  for  hauling  water,  coal,  oil,  brushes,  etc.,  interest  and  depre- 
ciation about  20  per  cent  of  the  cost  o'f  the  roller  plant.   An  average 
is  about  28  cents  per  cubic  yard. 

IV.  Cost  of  cleaning  and  scraping.     This  depends  upon  the 
width,  nature,  and  situation  of  the  road,  the  nature  of  the  traffic, 
and  the  quality  of  the  stone.     Much  diversity  of  opinions  exists  as 
to  the  frequency  and  methods  of  cleaning,  and  scraping,  but  it  is 
generally  conceded  that  a  road  should  be  scraped   as  soon  as  the 
thickness  of  the  mud  reaches  one-fourth  of  an  inch.   But  scraping  is 
not  the  best  or  cheapest  form  of  cleaning  a  road.     Mud  is  but  the 
refuse  of  a  road  with  water  added.     If  this  refuse  is  removed  when 
the  road  is  dry,  and  in  consequence  dusty,  a  hand  or  machine  broom 
can  remove  nearly  three  times  as  much  dust  as  can  be  scraped  off 
in  the  form  of  mud,  and  the  surface  of  the  road  will  not  be  injured 
or  torn  up.     One  sweeping  will  generally  clean  a  road  perfectly: 
whereas  when  a  scraper  is  employed  it  must  be  gone  over  three  or 
four  times  before  the  surface  is  clean;  but  under  certain  conditions 
of  the  atmosphere  the  surface  of  the  road  is  too  sticky  to  allow  of 


MAINTENANCE. — REPAIRING  j    CLEANSING  ;   WATERING.      595 

sweeping,  and  at  such  times  it  is  impossible  to  do  without  a  scraper. 
Its  use  should  be  as  limited  as  possible,  for  it  will  permanently 
damage  a  road  more  quickly  than  any  other  method  by  pulling  up 
the  compacted  stone. 

V.  The  cost  of  cleaning    up    the    sides  of  the   road,  ditches, 
etc.,  and   keeping  open    ivatercourses.     This    depends   upon    the 
frequency   with   which    it   will  have  to    be  done;  usually   three 
times  a  year  is  sufficient,  and  an  average  price  is  $15  per  cleaning 
per  mile. 

VI.  The   cost   of  sprinkling.     This    depends    upon     the   fre- 
quency of  sprinkling  and  accessibility  of  water,  and  is  made  up  of 
team  labor  for  hauling  the  sprinkling-cart,  wages  of  driver,  cost  of 
water,   interest,  and  depreciation  of  the   sprinkling-plant.      The 
average  number  of  days  on  which  sprinkling  is   needed   is   180; 
number  of  daily  sprinklings,  once  per  day  per  mile;  average  cost, 
70  cents  per  mile. 

To  these  items  must  be  added  a  certain  sum  (about  $5)  per 
mile  for  repair  and  replacing  of  tools,  etc.,  and  about  5  per  cent  on 
the  total  cost  to  cover  the  administrative  charges. 

Combining  these  factors  in  the  following  manner  will  give  the 
probable  cost  of  maintenance  per  mile  of  a  given  road : 

Let  N  =  average  number  of  cubic  yards  of  stone  spread  per 

mile; 

A  =  cost  per  cubic  yard  of  stone  in  depots; 
L  =  cost  of  preparing  road-surface  and  spreading  stone; 
R  =  cost  per  cubic  yard  of  rolling; 

C  =  average   number   of   times   sides   will  require  clean- 
ing; 

c  =  cost  of  cleaning  sides,  etc.,  per  mile; 
S  —  average   number  of  times   road   will   require   clean- 
ing; 

s  =  cost  of  cleaning  per  mile; 

W  =  average   number  of  times  road  will  require  sprink- 
ling; 


59G  HIGHWAY    CONSTRUCTION. 


w  =  cost  of  sprinkling  per  mile; 
D  —  annual  depreciation  and  renewal  of  hand  tools; 
/=  cost  of  administration,  say  5  per  cent  of  total  cost; 
X=  cost  of  maintenance  per  mile  per  annum. 

Then 

X=  N(A  +L  +  R)  +  Cc  +  S8+Ww  +  D  +  L 

If  the  stone  is  quarried  by  day's  labor,  its  cost  will  be 
A  =  q  +  b  + 

in  which  q  =  cost  of  quarrying; 
Z>  =  cost  of  breaking; 
li  =  cost  of  hauling; 
p  =  cost  of  stacking. 


861.  Repair. — When  the  thickness  of  the  covering  is  so  reduced 
that  it  is  necessary  to  re-cover  it  with  stone,  let  it  be  done  in  sec- 
tions as  large  as  convenient.     The  stone  should  be  spread  and  rolled 
in  the  same  manner  as  directed  for  building.     As  a  rule,  in  re-coat- 
ing, the  thickness  need  not  be  more  than  two  or  three  stones.     The 
periods  at  which  re-coating  will  be   required   depend   upon  the 
quantity  of  the  traffic,  and  will  vary  from  three  to  five  years. 

862.  Organization  of  Road  Force. — For  the  proper  care  of  a 
roadway   an   adequate    amount   of    skilled   laborers   permanently 
employed  is  necessary.     This  labor   should  be  employed  by  the 
community,  and  be  under  the  direct  orders  and  supervision  of  the 
county  engineer.     The  force  should  be  arranged  as  follows :  county 
engineer,  inspectors  (assistant  engineers),  chief  foreman,  foremen, 
laborers. 

The  number  of  men  required  will  depend  upon  the  amount  of 
the  traffic.  With  light  traffic  one  laborer  will  be  required  to  every 
4  miles ;  with  heavy  traffic  and  a  wide  road  one  man  will  be  required 
to  every  mile.  In  the  spring  and  fall  extra  help  will  be  required ; 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.        597 

the  extra  men  should  be  directed  by  the  permanent  roadman  on 
each  section,  whose  knowledge  of  his  section  will  enable  him  to 
employ  them  to  the  best  advantage. 

Chief  Foreman. — There  will  be  required  one  chief  foreman  for 
every  100  miles  of  road.  His  duties  shall  be  to  superintend  the 
entire  road  management  under  direct  orders  from  the  County 
Engineer,  received  either  from  himself  or  his  assistants.  He 
shall  have  no  power  to  engage  or  discharge  any  foreman  without 
first  reporting  to  the  engineer,  but  shall  have  full  authority  over 
the  laborers.  He  shall  set  out  and  direct  all  work  for  the  fore- 
men, shall  OK  the  foremen's  requisitions  for  tools,  supplies, 
horse-labor,  etc.  He  shall  under  no  circumstances  purchase  tools, 
materials,  or  employ  special  labor  unless  the  requisition  there- 
for is  signed  by  the  engineer,  in  cases  to  avert  an  accident  or  to 
save  expense  alone  excepted.  He  shall  walk  the  district  in  his 
charge  as  far  as  practicable,  and  carefully  take  and  keep  notes  of 
work  required  to  be  done,  inspect  all  bridges  and  structures.  He 
shall  examine  the  foremen's  book  and  see  that  all  accounts  are 
properly  entered. 

He  shall  keep  an  order  and  tool  account,  a  material,  team, 
and  general  expenditure  book,  also  a  careful  diary  of  his  day's  do- 
ings. He  shall  work  the  same  hours  as  the  workmen,  and  do  his 
utmost  to  skilfully  manage  and  check  all  extravagance,  filling  up  any 
spare  time  in  doing  necessary  work.  In  the  absence  of  any  fore- 
man he  shall  take  his  place  and  direct  the  work  until  new  arrange- 
ments can  be  made.  He  will  have  charge  of  the  steam  road-roller 
and  be  responsible  for  the  economical  working  of  the  same. 

Foreman. — The  best  men  obtainable  should  be  employed  for 
this  work.  They  should  have  about  ten  miles  of  ordinary  country 
road  to  superintend,  varying,  of  course,  very  much  with  the  traffic; 
they  should  live  as  near  as  is  practicable  to  the  centre  of  their 
sections.  They  should  not  be  changed  from  one  section  to  another, 
but  be  retained  permanently  in  the  same  section. 

Each  foreman  should  be  supplied  with  a  blank  diary,  in  which 
he  should  write  up  every  day  the  work  he  is  engaged  upon;  each 
page  so  written  to  be  initialed  by  the  chief  foreman.  This  diary 
should  always  be  in  his  possession  while  on  the  road,  and  should 
always  be  ready  for  examination  by  the  inspector  or  engineer,  who- 


598  HIGHWAY   CONSTRUCTION". 

-will  note  in  it  the  date  of  examination.  The  foreman  will  also  be 
supplied  with  a  time-book  in  which  to  keep  his  own  and  his  men's 
time;  also  with  an  account-book  in  which  he  will  note  the  recep- 
tion and  weight  of  all  material,  keep  an  account  of  all  tools, 
extra  labor,  team-hire,  blacksmith  and  all  other  accounts  of  his 
section. 

The  foreman  shall  take  all  necessary  instructions  from  the  chief 
foreman,  and  in  his  absence  all  orders  from  the  inspector  or 
engineer  must  be  promptly  carried  out.  They  shall  work  them- 
selves and  see  that  the  work  is  properly  carried  out  on  their  section. 
They  shall  have  no  power  to  discharge  or  engage  any  workman 
without  first  reporting  the  matter  to  the  chief  foreman. 

Tools. — Every  foreman  should  be  supplied  with  the  following 
tools  for  the  use  of  the  men  under  him  and  himself :  shovels,  pick- 
axes, spades,  hoes,  rakes,  rammers,  wheelbarrows,  brush-hooks, 
axes,  scrapers,  brooms,  stone-sledges,  stone-hammers,  straight-edge, 
level,  line. 

.  The  tools  should  be  repaired  by  the  nearest  blacksmith,  under 
contract  for  a  year  or  more  at  schedule  rates,  and  before  any  tools 
are  repaired  the  foreman  shall  give  a  written  order  to  the  smith 
and  preserve  a  duplicate  himself. 

Whether  the  county  shall  -purchase  a  stone-crusher  or 
not  will  depend  upon  circumstances,  whether  stone  is  to  be 
liad  in  the  county  or  not,  or  whether  it  can  be  purchased 
cheaper. 

Roller. — The  prpper  maintenance  of  a  road  cannot  be  carried 
out  without  the  employment  of  a  roller.  If  the  extent  of  the  road 
will  not  warrant  the  purchase  of  a  steam-roller,  a  horse-roller  should 
be  secured.  Whichever  kind  of  roller  is  used,  its  weight  should 
not  be  less  than  4  tons  and  need  not  exceed  10  tons ;  the  weight 
per  inch  of  width  is  more  important  than  the  gross  weight  of  the 
machine. 

Team-labor  and  Materials. — All  team-labor  and  materials  should 
be  supplied  under  contract.  The  chief  foreman  of  the  section 
will  keep  the  time  of  all  horse-labor  and  give  time-checks  for  the 
same.  If  stone  is  purchased,  it  should  be  bought  by  weight,  and 
each  load  delivered  should  be  weighed  on  a  public  weighing 
machine,  and  the  weight-check  delivered  to  the  foreman  receiving 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.      599 

the  material,  who  in  turn  will  deliver  to  the  carter  a  receipt  in  the 
form  furnished  for  the  purpose. 

Accounts. — Accounts  of  all  kinds  should  be  sent  to  the  County 
Engineer  direct  as  soon  as  the  work  or. contract  is  complete,  and 
no  account  should  under  any  circumstances  be  passed  unless 
accompanied  by  the  necessary  order  for  the  work  being  carried 
out. 

Requisitions  for  tools,  etc.,  should  be  sent  in  by  the  foreman  at 
-a  fixed  date  in  each  month,  and  a  date  be  fixed  for  their  issuance. 

Snow. — When  snow  has  fallen  heavily  or  is  drifting,  the  road- 
guard  must  shovel  it  off  the  road  so  as  to  keep  a  track  open.  If  he 
is  unable  to  do  this  with  the  assistance  of  hired  laborers,  he  must 
make  requisition  for  extra  help.  If,  on  account  of  continued  drift- 
ing, the  road  cannot  be  kept  open,  the  travel  may  be  temporarily  led 
over  the  adjoining  fields,  care  being  taken  to  mark  the  location  of 
the  temporary  road  by  poles  and  wisps  of  straw  or  tree-branches. 
When  the  weather  permits  sleighing  for  some  time,  loose  stones 
and  gravel  liable  to  cause  accidents  are  to  be  removed,  and  bare 
spots  are  to  be  covered  with  snow. 

When  thaw  sets  in,  all  snow  and  ice  on  the  roads  must  be 
speedily  removed. 

County  Engineer. — The  County  Engineer  with  the  aid  of  his 
assistants  will  take  direct  management  of  all  the  roads,  set  out  all 
work  and  give  directions  to  the  chief  foreman,  and,  in  general, 
superintend  the  carrying  out  of  all  work,  make  plans  and  prepare 
estimates  for  all  materials,  keep  all  accounts  and  perform  all  in- 
cidental duties. 

Storage  and  Delivery  of  Broken  Stone. — Depots  or  spaces  for 
the  storage  of  the  broken  stone  should  be  provided  along  the  sides 
of  the  road ;  these  depots  should  be  close  enough  together  for  the 
roadmen  to  wheel  out  the  stone  to  the  intervening  portions  of  the 
road. 

The  contractor  should  be  required  to  deliver  the  broken  stone 
at  each  of  these  depots  at  such  times  and  in  such  quantities  as  the 
engineer  may  direct.  The  stone  heaped  up  at  the  depots  should 
not  be  allowed  to  encroach  upon  the  road  or  interfere  with  the 
gutters;  one  or  two  cubic  yards  will  be  a  sufficient  quantity  to  have 
at  each  depot.  A  convenient  size  for  the  stone-heaps  will  be  6  feet 
long,  3  feet  wide,  and  1-j-  fee^  high.  Such  a  heap  will  contain  1  cubic 


600  HIGHWAY    CONSTRUCTION. 


yard,  and  the  quantity  so  stored  can  be  ascertained  by  measurement 
at  any  time. 

863.  Records. — It  is  very  desirable  that  those  in  charge  of  roads 
should  adopt  some  form  of  record,  showing  plainly  the  cost  of 
materials,  of  labor,  and  of  any  miscellaneous  expenditures  connected 
with  the  maintenance  of  roads.     Comparisons  of  the  total  cost  of 
different  roads,  and  of  the  proportion  of  expenditure  for  materials 
and  labor,  and  for  other  things,  would  be  facilitated,  and  a  step 
would  be  taken  towards  gathering  statistics  relating  to  road-mairi- 
tenance  which  are  at  present  wanting  in  both  America  and  Eng- 
land. 

864.  Instructions  to  Roadmen  (published  by  the  Eoad  Improve- 
ment Association  of  No.  57  Basinghall  Street,  London,  E.  C.)  will 
be  found  useful  to  roadmen,  and  are  therefore  submitted  in  ex- 
tenso: 

(1)  Never  allow  a  hollow,  a  rut,  or  a  puddle  to  remain  on  a  road, 
but  fill  it  up  at  once  with  chips  from  the  stone-heap. 

(2)  Always  use  chips  for  patching,  and  for  all  repairs  during 
the  summer  months. 

(3)  Never  put  fresh  stones  on  the  road  if  by  cross-picking  and 
a  thorough  use  of  the  rake  the  surface  can  be  made  smooth  and 
kept  at  the  proper  strength  and  section. 

(4)  Remember  that  the  rake  is  the  most  useful  tool  in  your 
collection,  and  that  it  should  be  kept  close  at  hand  the  whole  year 
round. 

(5)  Do  not  spread  large  patches  of  stone  over  the  whole  width 
of  the  road,  but  coat  the  middle  or  horse  track  first,  and  when  this 
has  worn  in,  coat  each  of  the  sides  in  turn. 

(6)  Always  arrange  that  the  bulk  of  the  stones  may  be  laid 
down  before  Christmas. 

(7)  In  moderately  dry  weather  and  on  hard  roads,  always  pick 
up  the  old  surface  into  ridges  six  inches  apart,  and  remove  all  large 
and  projecting  stones  before  applying  a  new  coating. 

(8)  Never  spread  stones  more  than  one  stone  deep,  but  add  a 
second  layer  when  the  first  has  worn  in,  if  one  coat  be  not  enough. 

(9)  Use  a  steel-pronged  fork  to  load  the  barrels  at  the  stone- 
heap,  so  that  the  siftings  may  be  available  for  "  binding"  and  for 
summer  repairs. 


MAINTENANCE. — EEPAIRING  ;    CLEANSING  ;    WATERING.       601 

(10)  Never  shoot  stones  on  the  road,  and  crack  them  where 
they  lie,  or  a  smooth  surface  will  be  out  of  question. 

(11)  Go  over  the  whole  of  the  new  coating  every  day  or  two 
with  the  rake,  and  never  leave  the  stones  in  ridges. 

(12)  Remove  all  large  stones,  blocks  of  wood,  and  other  obstruc- 
tions  (used   for   diverting  the  traffic)  at  nightfall,  or  the  conse- 
quences may  be  serious. 

(13)  Never  put  a  stone  upon  a  road  for  repairing  purposes  that 
will  not  pass  freely  in  every  direction  through  a  2- inch  ring,  and 
remember  that  still  smaller  stones  should  be  used  for  patching  and 
for  all  slight  repairs. 

(14)  Recollect  that  hard  stone  should  be  broken  to  a  finer  gauge 
than  soft,  but  that  the  2-inch  gauge  is  the  largest  that  should  be 
employed  under  any  circumstances  where  no  steam  roller  is  em- 
ployed. 

(15)  Never  be  without  your  ring-guage.     It  should  be  to  the 
roadman  what  the  compass  is  to  the  mariner. 

(16)  If  you  have  no  ring-gauge,  remember  MacAdam's  advice 
that  any  stone  you  cannot  put  easily  into  your  mouth  should  be 
broken  smaller. 

(17)  Use  chips,  if  possible,  for  binding  newly-laid  stones  to- 
gether, and  remember  that  road-sweepings,  horse-droppings,  sods 
of  grass,  and  other  rubbish,  when  used  for  this  purpose,  will  ruin 
the  best  road  ever  constructed. 

(18)  Remember  that  water-worn  or  rounded  stones  should  never 
be  used  upon  steep  gradients,  or  they  will  fail  to  bind  together. 

(19)  Never  allow  dust  or  mud  to  lie  on  the  surface  of  the  road, 
for  either  of  these  will  double  the  cost  of  maintenance. 

(20)  Recollect  that  dust  becomes  mud  at  the  first  shower,  and 
that  mud  forms  a  wet  blanket  which  will  keep  a  road  in  a  filthy 
condition  for  weeks  at  a  time,  instead  of  allowing  it  to  dry  in  a 
few  hours. 

(21)  See  that  all  sweepings  and  scrapings  are  put  into  heaps 
and  carted  away  immediately. 

(22)  Remember  that  the  middle  of  the  road  should  always  be  a 
little  higher  than  the  sides,  so  that  the  rain  may  run  into  the  side 
gutters  at  once. 

(23)  Never  allow  the  water-tables,  gutters,  and  ditches  to  clog 
up,  but  keep  them  clear  the  whole  year  through. 


602  HIGHWAY   CONSTRUCTION. 

(24)  Always  be  upon  your  road  in  wet  weather,  and  at  once 
fill  up  with  "  chips  "  any  hollows  or  ruts  where  the  rain  may  lie. 

(25)  When  the  main  coatings  of  stone  have  worn  in,  go  over 
the  whole  road,  and,  gathering  together  all  the  loose  stones,  return 
them  to  the  stone-heap  for  use  in  the  winter  to  follow ;  for  loose 
stones  are  a  source  of  danger  and  annoyance  and  should  never  be 
allowed  to  lie  on  any  road. 

865.  The  French  System  of  Highway  Maintenance.— The  sys- 
tem of  highway  maintenance  adopted  by  the  French,  whose  roads 
are  unexcelled  by  any  is  as  follows : 

The  roads  are  divided  into  national,  departmental,  military,  and 
vicinal  or  country  cross-roads. 

The  national  roads  are  maintained  entirely  at  the  expense  of 
the  public  treasury;  the  departments  provide  for  the  second  class 
of  roads,  and  also  partly  for  the  military  roads;  the  local  cross- 
roads are  maintained  by  the  communes,  or  when  of  higher  impor- 
tance by  the  departments. 

The  national  roads  aggregate  upwards  of  23,180  miles  in  length, 
of  which  1632  miles  are  paved  like  a  street.  These  roads  average 
in  width  16  metres  or  52  feet  6  inches,  of  which  19.68  feet  is  for 
the  wheelway,  19.68  feet  for  the  sidewalks,  and  13.12  feet  for  the 
ditches  and  embankment  slopes.  The  department  roads  are  not 
quite  so  wide,  their  average  width  being  39  feet.  The  aggregate 
length  of  the  latter  is  about  29,167  miles.  The  military  roads 
number  28,  and  are  about  932  miles  long  in  all.  They  are  chiefly 
in  the  west  of  France,  laid  out  after  the  last  insurrection  of  Ven- 
dee. The  sum  of  about  $6,800,000  is  yearly  expended  in  making 
new  roads  or  repairing  old  ones,  and  $32,000,000  is  expended  for 
maintenance  and  inspection. 

The  cross-roads  are  managed  by  a  special  branch  of  the  depart- 
ment of  the  Minister  of  the  Interior,  a  branch  which  employs 
about  3000  inspectors  and  42,000  workmen,  specially  charged 
with  the  duty  of  keeping  these  roads  in  repair.  In  1872  these 
cross-roads  aggregated  338,273  miles  in  length  and  covered  a 
surface  of  about  915,000  acres.  To  the  very  considerable  sum 
which  the  communes  must  apply  to  the  extension  and  repair  of 
these  country  roads,  the  government  used  to  add  a  yearly  grant  of 
$2,300,000;  but  since  1873  this  sum  has  been  reduced  to  $1,150,000 
annually. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       603 

The  care  of  the  national  roads  is  a  large  part  of  the  duties  of 
the  "  Engineers  of  Bridges  and  Eoads "  (Ingenieurs  des  Fonts  et 
Chaussees)  and  belongs  to  the  portfolio  of  the  Minister  of  Public 
"Works. 

In  each  department  there  is  appointed  by  the  Minister  of 
Public  Works  an  engineer-in-chief,  who  has  the  direction  and 
responsibility  of  the  work  of  maintenance  of  such  portion  of  the 
national  roads  as  lie  within  that  department.  He  is  also  placed  in 
•charge  of  some  other  work  in  that  department;  either  of  rail- 
roads, canal  or  river  improvements,  or  the  care  of  the  seaports, 
if  such  lie  in  that  department. 

Sometimes  he  is  also  in  charge  of  the  departmental  roads,  and 
in  a  few  cases  of  the  county  roads  as  well.  Under  him  are  several 
Engineers-in-ordinary  (Ingenieurs  ordinaires),  who  are  employed 
only  in  a  certain  section  of  the  department;  each  one  having 
charge  of  the  work  in  an  arrondissement. 

There  they  direct  the  repairs  according  to  the  general  plans 
of  their  chief,  but  at  the  same  time  they  are  allowed  consider- 
able latitude  to  display  their  ability  or  originality  and  follow  out 
their  own  ideas  in  the  details  of  the  work.  Their  duties  require 
them  to  visit  carefully  at  least  four  times  a  year,  oftener  if 
necessary,  every  road  confided  to  their  care. 

The  next  grade  below  the  engineers-in-ordinary  is  that  of 
•Conductor  or  Assistant  Engineer. 

The  conductor  has  a  subdivision  comprising  a  length  such 
that  he  may  be  able  to  inspect  it  in  detail  at  least  twice  each 
month  and  still  have  sufficient  time  to  attend  to  the  other  require- 
ments of  the  service  with  which  the  chief  is  charged,  i.e.,  of 
bridges,  railroads,  canals,  seaports,  etc. 

The  supervision  comprises  usually  from  25  to  50  miles  of  road, 
according  to  the  distribution  and  the  complexity  of  their  main- 
tenance, and  of  other  details  connected  with  them.  The  con- 
ductor makes  semi-monthly  inspections  of  the  roads  under  his 
charge,  and,  further,  he  makes  his  tour  of  inspection  on  foot. 

He  gives  orders  to  the  foremen  of  the  different  gangs  at  work 
along  the  roads.  He  keeps  a  record  of  their  work,  to  see  that  they 
do  a  proper  amount.  If  any  have  been  guilty  of  neglect,  he  may 
recommend  to  his  chief  that  they  be  punished. 

Following  each  regular  inspection  he  forwards  a  written  report 


604  HIGHWAY   CONSTRUCTION. 


to  the  engineer  in  charge  of  that  division.  He  keeps  the  accounts 
for  his  division.  He  is  consulted  by  the  engineer  in  case  of  the 
receipt  of  any  petition  or  other  affairs  upon  which  his  accurate 
knowledge  of  the  division  would  make  him  capable  of  giving 
information  or  advice. 

If  any  surveys  are  to  be  made,  he  makes  them.  He  also 
inspects  all  road  material,  all  of  which  is  furnished  by  contract,, 
and  has  immediate  charge  of  the  construction  of  all  new  work. 

The  engineer  can  give  no  order  to  the  laborers  without  giving 
it  through  the  conductor. 

In  districts  where  there  is  much  to  do  he  is  aided  by  a  second 
assistant  engineer. 

This  is  the  grade  held  by  the  younger  engineers,  who  have  charge 
of  the  drafting  and  clerical  work  in  the  chief-engineer's  office,  and 
also  assist  in  the  outdoor  work  when  there  is  a  press  of  it. 

It  is  from  the  ranks  of  these  latter  that  by  promotion  the  corps 
of  assistant  engineers  or  conductors  is  kept  up  to  the  required 
number.  Their  promotion  is  made  on  their  successfully  passing 
examinations  for  that  purpose. 

Under  the  conductor  comes  the  road  laborer  or  cantonnieiv 
The  road  laborers  are  divided  into  squads  of  five  or  six.  Each  one 
is  in  charge  of  an  overseer,  chosen  from  one  of  their  number. 

Each  of  the  road  laborers  has  charge  of  a  length  of  road  varying 
from  1-J-  to  2£  miles,  depending  upon  the  condition  of  the  road,  the 
amount  of  circulation,  and  the  method  of  maintenance,  which 
would  depend  upon  the  nature  of  its  construction. 

When  there  happens  to  be  much  work  to  be  done  at  once,  a 
few  laborers  by  the  day  are  hired  to  assist,  but  they  are  reduced  to 
the  least  possible  number. 

If  there  is  to  be  work  that  will  require  extra  laborers  for  a 
considerable  length  of  time,  they  organize  another  road  gang,  BO» 
that  the  work  will  be  done  by  regular  hands. 

866.  Regulations  for  Cantonniers  (Road  Laborers). 

Definition  of  the  Work  of  Cantonniers. — The  cantonniers  are 
charged  with  the  manual  labor  connected  with  the  daily  main- 
tenance of  the  roads,  over  a  definite  length  of  road,  called  a  canton. 

They  must  obey,  in  everything  relating  to  their  work,  the 
engineers,  foremen,  and  other  agents  of  the  administration  of 
roads  and  bridges. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       605 

Nomination  of  Cantonniers. — The  cantonniers  are  nominated 
l3y  the  prefect,  from  a  list  submitted  to  the  chief  engineer,  con- 
taining three  times,  or  at  least  twice,  the  number  of  candidates 
required  to  fill  the  vacancies.  They  are  dismissed  by  the  prefect 
on  the  advice  of  the  chief  engineer. 

Conditions  of  Admission. — To  be  nominated  a  cantonnier  it  is 
necessary  (1)  to  have  fulfilled  the  laws  relating  to  service  in  the 
army,  and  to  be  not  more  than  45  years  old;  (2)  not  to  be  subject 
to  any  infirmity  which  may  hinder  daily  and  diligent  labor;  (3)  to 
have  worked  on  the  construction  or  repair  of  roads;  (4)  to  have  a 
certificate  of  good  conduct  from  the  mayor  of  the  commune  or  the 
subprefect  of  the  arrondissement. 

Candidates  who  can  read  and  write  will  be  preferred. 

Chief  Cantonnier. — The  cantons  of  the  roads  in  a  department 
shall  be  grouped  in  districts  containing  at  least  six  cantons.  The 
six  cantonniers  will  constitute  a  brigade  ;  one  of  them  shall  be  chief 
cantonnier;  he  must  be  able  to  read  and  write,  and  shall  be  chosen 
from  the  cantonniers  distinguished  for  zeal,  good  conduct,  and  in- 
telligence. 

The  chief  cantonniers  shall  have  a  shorter  length  than  other  can- 
tonniers, so  that  they  may  be  able  to  attend  to  special  duties 
allotted  to  them.  They  shall  accompany  the  foremen  in  their 
rounds,  and  note  the  orders  which  may  be  given  by  the  cantonniers 
of  their  brigade,  and  see  that  the  orders  are  carried  out.  They  shall 
accordingly  go  over  the  whole  extent  of  their  district  at  least  once 
a  week,  varying  the  days  and  hours  of  their  visits,  to  satisfy  them- 
selves of  the  presence  of  the  cantonniers,  and  to  direct  them  in  their 
-work;  they  shall  report  to  those  under  whose  orders  they  are  more 
particularly  placed,  and  shall  furnish  to  the  engineers  all  the  infor- 
mation that  may  be  required  of  them. 

They  may  be  temporarily  employed  in  superintending  and  keep- 
Ing  account  of  the  works  of  re-dressing  the  paved  causeways,  and 
in  directing  itinerant  gangs  of  workmen. 

Distinctive  Marks  of  Cantonniers.— Cantonniers  shall  wear  a 
blue  jacket  and  a  leather  hat,  round  which  shall  be  a  band  of  copper 
0.28  m.  long  and  0.055  m.  broad,  with  the  word  "  cantonnier  "  cut 
out  in  it.  The  chief  cantonniers  shall  wear  besides  on  the  left  arm 
an  armlet  of  the  prescribed  pattern. 

There  shall  be  given  besides  to  each  man  a  mark  consisting  of 


GOG  HIGHWAY   CONSTRUCTION. 

a  staff  2  metres  long,  divided  in  decimetres,  shod  with  iron,  and 
furnished  at  the  top  with  a  strong  iron  plate  0.24  m.  wide  and 
0.16  m.  high,  on  each  side  of  which  shall  be  shown  in  letters  0.08  m.. 
high  the  number  of  the  canton.  This  mark  must  always  be 
set  up  on  the  road  at  less  than  100  metres  from  where  the  cantonnier 
is  at  work. 

The  Work  of  the  Cantonniers. — The  work  of  the  cantonniers 
consists  in  maintaining  and  repairing  the  roads  daily  and  constantly, 
so  that  they  may  be  dry,  clean,  and  smooth,  safe  in  times  of  hard 
frost,  and  of  a  satisfactory  appearance  at  all  seasons. 

To  effect  this,  they  must,  subject  to  the  orders  and  instructions, 
which  may  be  given  them  in  case  of  need : 

(1)  Insure  the  flowing  off  of  water  by  cleansing  the  gutters, 
pipes,  etc.,  by  making  small  drains  for  the  purpose  wherever  they 
may  be  necessary,  taking  care  that  these  drains  should  never  be 
made  in  the  body  of  the  road. 

(2)  At  suitable  times  open  and  maintain  the  ditches,  regulate 
the  sides,  throwing  the  surplus  earth  on  the  neighboring  ground,  if 
there  is  no  objection,  or  putting  it  together  to  facilitate  its  measure- 
ment or  removal. 

(3)  Remove  as  soon  as  possible  with  a  scraper  or  shovel  all  liquid 
or  soft  mud  from  the  whole  breadth  of  the  road,  even  if  there  be 
neither  hollows  nor  ruts,  and  collect  the  mud  in  regular  heaps  on 
the  sides  to  be  measured,  if  there  is  room  for  it  there. 

(4)  Spread  the  mud,  when  dry,  on  the  sides  which  have  lost 
their  shape  or  have  a  slope  of  more  than  1  in  25  from  the  road,  and 
throw  the  surplus  on  the  neighboring  fields,  if  not  objected  to. 

(5)  At  the  approach  of  winter  redouble  attention  to  all  that  is 
prescribed  in  the  two  preceding  paragraphs,  to  prevent  lumps  of 
frozen  mud. 

(6)  In  dry  weather  remove  the  dust  and  deposit  it  on  the  sides. 

(7)  Clear  away  the  snow  from  the  whole  breadth  of  the  road,  or 
at  least  from  the  middle,  particularly  at  places  where  it  accumulates 
and  obstructs  the  traffic;  throw  it  immediately  on  the  neighboring 
fields  if  possible,  or  collect  it  in  heaps  on  the  sides,  so  as  to  show 
drivers  of  vehicles  where  the  road  is. 

(8)  Break  and  remove  ice  from  the  road,  and  scatter  sand  and 
rubble,  especially  at  the  sides  and  at  sharp  turnings. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       607 

(9)  Also  break  the  ice  in  the  ditches  and  remove  it  where  it 
accumulates,  so  as  to  threaten  flooding  of  the  road  in  the  thaw. 

(10)  In  the  time  of  thaw  assist  the  flowing  off  of  the  water  and 
remove  pieces  of  ice,  mud,  and  dirt,  so  that  the  effects  of  the  thaw 
may  prejudice  the  traffic  and  road  as  little  as  possible. 

(11)  Collect,  break,  and  stack  in  separate  heaps  and  in  a  par- 
ticular  shape  all  loose  stones,  and  those   projecting  or  only  just 
showing  if  too  large,  and  those  near  in  the  neighboring  fields  which 
can  be  used  for  the  purposes  of  the  road.     Break  the  materials 
intended  for  maintenance,  if  the  breaking  is  not  done  by  the  con- 
tractor. 

(12)  Cut  or  dig  up  thistles  or  other  weeds,  especially  before 
their  flowering  season. 

(13)  Clear  away  loose  stones  for  the  road  and  everything  which 
may  hinder  the  traffic. 

(14)  Clean  and  clear  away  earth,  plants,  and  extraneous  matters 
from  the  plinths,  string-courses,  and  parapets  of  bridges,  etc. 

(15)  Look  after  the  preservation  of  mile-stones,  sign-posts,  and 
bench-marks  on  the  road. 

(16)  Cultivate  and  look  after  plantations  belonging  to  the  State, 
see  to  their  preservation  and  to  that  of  plantations  of  private 
owners,  straighten  provisionally  all  young  trees  bent  by  the  wind, 
and  do  generally  all  that  the  welfare  of  the  road  demands,  con- 
formable to  more  particular  instructions  given  by  the  engineers  of 
the  district  for  carrying  out  the  above  general  orders. 

Employment  of  Materials. — On  roads  in  a  state  of  repair  the 
road  laborers  shall  conform  to  the  following  rules  for  employment 
of  materials. 

The  materials  shall  be  made  use  of  as  they  are  required,  always 
choosing  damp  weather  for  their  employment,  avoiding  wholesale 
coating  and  throwing  down  stones  at  random. 

To  proceed  regularly,  care  should  be  taken  to  observe  in  time  of 
rain  the  hollows  and  tracks  of  vehicles,  which  perceptibly  alter  the 
shape  of  the  road. 

These  worn  parts  should  be  cleaned  and  picked,  particularly  at 
the  edges,  but  only  to  the  depth  necessary  to  insure  the  binding  of 
the  materials.  The  materials  arising  from  the  picking  should  be 
cleared  of  earth  and  broken  if  necessary  before  being  used. 

The  filling  up  of  the  hollows  or  wheel-tracks  should  be  effected 


008  HIGHWAY   CONSTRUCTION. 

with  the  debris  and  with  the  necessary  quantity  of  new  material 
received  through  the  engineer.  It  must  be  carefully  beaten  so  as 
to  incorporate  it  with  the  lower  layer,  and  then  made  to  conform  to 
the  contour  of  the  road.  The  parts  thus  restored  should  be  main- 
tained with  particular  care  until  they  are  completely  consolidated. 

With  respect  to  roads  which  are  not  in  a  good  state  of  repair, 
but  which  nevertheless  are  open  for  traffic,  one  should  endeavor  to 
keep  them  in  as  good  a  condition  as  possible  by  employing,  with 
the  care  which  has  just  been  indicated,  the  materials  available. 

All  large  or  projecting  stones  should  be  taken  out,  as  they 
cause  damage,  and  they  should  be  broken  to  a  proper  size  before 
being  used  again. 

The  coatings  more  or  less  extensive  to  be  made  on  worn  roads 
will  be  prescribed  by  the  engineer,  who  will  also  decide  on  the 
materials  to  be  used.  The  hollows  and  ruts  to  be  filled  up  must 
first  be  cleared  of  mud  and  earth,  and  their  surface  then  picked  to 
a  depth  of  from  4  to  5  centimetres  (1£  to  2  inches).  The  materials 
should  not  be  spread  except  in  layers  of  from  5  to  6  centimeters  (2 
to  2£  inches),  which  should  be  carefully  beaten  and  consolidated. 

Task-work  to  be  performed. — To  stimulate  and  maintain  the 
activity  of  the  cantonniers,  the  engineers,  inspectors,  and  foremen 
shall  assign  them  work  to  be  performed  in  a  given  time,  whenever 
local  circumstances  permit  it.  A  summary  of  information  on  these 
tasks  shall  be  entered  in  that  part  of  the  cantonnier's  book  re- 
served for  the  instructions  of  the  service. 

Work  thus  prescribed  shall  be  one  of  the  principal  objects  of 
supervision  by  the  immediate  head  of  the  cantonniers,  as  well  as  by 
the  mayors  and  road  commissioners. 

Determination  of  Working  Hours. — From  the  1st  of  May  to 
the  1st  of  September  the  cantonniers  shall  be  on  the  roads,  with- 
out quitting  them,  from  5  o'clock  in  the  morning  to  7  o'clock  in 
the  evening.  The  rest  of  the  year  they  shall  be  there  from  sunrise 
to  sunset.  They  shall  take  their  meals  on  the  road  at  hours  fixed 
by  the  chief  engineer.  The  total  duration  of  meals  shall  not 
exceed  two  hours,  but  during  great  heat  it  may  be  prolonged  to 
three  hours. 

Removal  of  Cantonniers. — Cantonniers  may  be  removed  either 
singly  or  in  brigades,  when  the  needs  of  the  service  imperatively 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       609 

require  it,  to  points  indicated  to  them.  These  displacements  shall 
not  take  place  except  under  an  express  order  from  the  engineer. 

Compulsory  Attendance  of  Cantonniers  in  time  of  Rain, 
Snow,  etc. — Rain,  snow,  or  other  inclemency  of  the  weather  shall 
not  be  a  pretext  for  the  absence  of  cantonniers;  they  must  in  such 
times  redouble  their  zeal  to  prevent  damage  and  keep  the  road  in 
good  condition  for  the  whole  extent  of  their  cantons.  They  are, 
however,  authorized  to  make  themselves  fixed  or  portable  shelters 
which  shall  not  interfere  with  the  public  way  or  adjoining  prop- 
erty, but  which  must  be  in  sight  of  the  road  and  less  than  10 
metres  off,  so  that  the  presence  of  the  workmen  can  always  be  as- 
certained. 

Gratuitous  Assistance  to  Travellers. — Cantonniers  must  render 
gratuitous  aid  and  assistance  to  drivers  and  travellers,  but  only  in 
•case  of  accidents. 

Surveillance  over  Breaches  of  Higlnvay  Laiv. — To  prevent  as 
much  as  possible  breaches  of  highway  law,  the  cantonniers  shall 
warn  travellers  and  occupiers  of  the  adjoining  lands  who  may  be 
disposed  to  commit  them.  They  shall  consequently  keep  an  eye  on 
repairs,  building,  deposits,  encroachments,  and  planting  which  may 
take  place  without  leave  on  the  highway.  They  shall  report  any 
such  breaches  to  the  surveyor,  either  when  he  makes  his  rounds, 
or  at  once  by  letter  or  by  message  through  the  chief  cantonnier. 

Tools  witli  wliicli  Cantonniers  must  be  provided. — Every  can- 
tonnier shall  be  provided,  at  his  own  expense,  with  a  wheelbarrow, 
an  iron  shovel,  a  wooden  shovel,  a  road-pick,  an  iron  road-scraper, 
a  wooden  road-scraper,  an  iron  rake,  an  iron  crowbar,  an  iron 
sledge-hammer,  and  a  line  20  metres  long. 

The  head  cantonniers  must  besides  be  provided  with  three  bon- 
ing rods  (rods  in  the  form  of  a  T  much  employed  in  European 
countries  to  range  in  grades,  etc.),  with  a  level  graduated  to  indi- 
cate gradients,  and  with  a  double  metre  measure. 

Tools  of  a  Particular  Kind  to  be  furnished  by  the  Administra- 
tion.— Each  cantonnier  shall  be  entrusted  with  an  iron  ring  6 
centimetres  (2-J-  inches)  in  diameter,  so  that  he  may  ascertain  if  the 
stones  which  he  has  to  spread  on  the  road  have  been  broken  ac- 
cording to  the  specifications. 

Providing  Tools  in  advance  to  Cantonniers. — Cantonniers  who 
have  no  means  of  procuring  them  can  have  any  tools  they  require 


610  HIGHWAY  CONSTRUCTIONS'. 

supplied  in  advance.  The  repayment  of  the  cost  of  these  tools 
will  be  insured  by  the  administration  by  stoppages,  which,  except 
in  cases  of  dismissal,  shall  not  exceed  one  sixth  of  the  monthly 
salary. 

Keeping  Tools  in  Repair. — Cantonniers  shall  keep  their  tools 
in  a  good  state  of  repair.  If  they  become  negligent  in  this  respect, 
they  will  be  repaired  by  the  administration,  and  the  expenses  will 
be  repaid  in  the  same  manner  as  for  new  tools. 

Tools  must  not  be  taken  to  be  repaired  during  working  hours. 
Excuses  for  absence  based  upon  the  necessity  of  getting  tools 
repaired  will  never  be  accepted. 

Cantonniers'  Books. — Every  cantonnier  will  be  provided  with  a 
book  suitably  ruled  and  headed,  in  which  he  will  make  notes  on  the 
work  and  conduct  of  the  laborers,  any  orders  and  instructions  given 
them,  and  information  of  the  work  which  has  been  assigned  to  them. 
It  must  be  presented  by  them  to  the  agents  charged  with  the  super- 
vision of  the  road,  every  time  they  are  required  to  do  so,  under 
penalty  of  the  stoppage  of  a  day's  pay  for  every  time  they  neglect 
to  produce  it,  or  three  days'  pay  in  the  case  of  having  lost  it. 

Means  of  Verifying  the  Absence  of  Cantonniers. — The  absence 
and  negligences  of  Cantonniers  will  be  verified  by  the  engineers  and 
the  agents  of  the  administration  employed  under  their  orders,  who 
will  make  a  note  of  them  in  the  books  just  spoken  of.  Absence 
can  also  be  verified  by  gendarmes  on  their  rounds,  by  mayors  of 
the  parishes  in  which  the  cantons  are  situated,  and  by  road 
commissioners. 

Leave  of  Absence  at  Harvest-time. — At  harvest-time,  when  the 
road  is  in  good  condition,  cantonniers  can  obtain  leave  of  absence 
from  the  engineer-in-ordinary,  when  authorized  by  the  engineer-in- 
chief .  They  will  receive  no  salary  while  on  leave  of  absence,  at  the 
expiration  of  which  they  must  return  punctually  to  their  posts  or 
they  will  be  immediately  superseded. 

Surrender  of  Book  and  of  Distinctive  Badges  on  Dismissal  of 
a  Cantonnier. — When  a  cantonnier  is  dismissed,  he  must  surrender 
to  the  engineer  his  book,  his  staff,  his  ring,  and  the  distinctive 
badges  which  he  wears  on  his  arm  and  cap.  Failing  to  do  this, 
double  the  value  of  these  articles  will  be  retained  from  that  which 
is  due  to  him  for  salary  at  the  time  of  his  dismissal. 

Classification    and    Salary    of  Cantonniers. — Cantonniers   of 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.      611 

each  department  will  be  divided  into  three  classes  of  equal  number, 
whose  salary,  for  each  class,  will  be  fixed  by  the  prefect,  on  the 
proposal  of  the  chief  engineer. 

The  classification  will  be  made  each  year  by  the  chief  engineer, 
on  the  report  of  the  engineer-in-ordinary,  and  according  to  the 
services  of  the  cantonniers  during  the  preceding  year. 

The  chief  cantonniers  will  be  divided  into  two  classes,  likewise 
of  equal  number. 

Their  salaries  will  be  fixed,  like  those  of  the  ordinary  canton- 
niers, by  the  prefect,  on  the  proposal  of  the  chief  engineer. 

The  cantonniers  receive  from  $10  to  $20  per  month,  and  the 
chief  cantonniers  receive  20$  more. 

Indemnity  for  Removal. — Cantonniers  who  leave  their  cantons 
by  order  of  the  engineer  will  receive  an  indemnity  of  one  fifth  more 
than  their  salary,  and  three  fifths  for  every  day  they  sleep  out. 

No  indemnity  for  removal  will  be  allowed  to  head  cantonniers 
except  when  they  go  out  of  the  district  of  their  brigade.  In  this 
case,  the  indemnity  to  which  they  are  entitled  will  be  regulated  in 
the  same  way  as  those  which  are  paid  to  ordinary  cantonniers. 

Annual  Gratuities. — Every  year,  on  the  report  of  the  engineer- 
in-chief,  the  prefect  may  grant  to  the  most  deserving  cantonnier  in 
each  district  of  the  engineer-in-ordinary,  a  gratuity,  which  shall 
not  exceed  a  month's  salary. 

A  similar  gratuity  may  also  be  awarded  to  that  one  of  the 
chief  cantonniers  of  the  department  who  shall  have  rendered 
the  best  service. 

Fines  on  Account  of  Absence. — Every  cantonnier  who  shall  not 
be  found  at  his  post  by  one  of  the  agents  having  a  right  of  super- 
vision on  the  road,  shall  be  subject  to  a  fine  of  three  days'  pay  for 
the  first  time,  of  six  days  in  case  of  a  second  offence,  and  be  dis- 
missed the  third  time. 

Those  who,  without  being  absent,  shall  not  have  done  enough 
work  during  the  month,  or  who  have  neglected  the  duty  entrusted 
to  them,  will  be  fined  enough  to  pay  for  repairing  any  damage 
resulting  from  their  negligence. 

A  part  of  these  fines  may  be  granted  by  the  engineer-in-chief,. 
on  the  report  of  the  engineer  in  ordinary,  for  the  benefit  of  those 
cantonniers  who  by  their  zeal  and  work  have  deserved  encourage- 
ment. 


612  HIGHWAY    CONSTRUCTION. 

867.  The  system  described  above,  while  employed  throughout 
France  for  the  maintenance  of  the  national  roads,  is  applied  to  all 
the  other  roads  in  but  27  of  the  87  departments. 

In  three  departments  the  engineer-in-chief  has,  it  is  true,  the 
direction  of  the  work,  but  has  under  him  a  different  corps  of 
engineers  or  commissioners  to  superintend  the  work  upon  the 
county  or  vicinal  roads. 

In  57  of  the  departments  a  commissioner  appointed  by  the 
Minister  of  the  Interior  has  charge  of  the  county  or  vicinal  roads. 
His  corps  comprises  commissioners  or  trustees  in  the  arrondissements 
and  cantons  who  are  appointed  by  the  prefect  of  the  department. 

The  ordinary  vicinal  roads  are  in  the  charge  of  the  mayors  of 
the  communes.  The  direct  agents  are  inspectors,  who  are  charged 
with  the  duty  of  watching  this  work,  and  are  responsible  for  its 
proper  execution. 

Inspectors. — The  chief  inspector  is  under  the  direct  authority 
of  the  prefect,  and  he  has  charge  of  all  the  vicinal  roads  of  the 
department,  and  all  the  sub-inspectors  are  under  his  orders.  He 
executes  the  laws  and  regulations  prescribed,  and  the  inspectors  of 
arrondissements  have  similar  power  in  their  own  districts.  The 
chief  inspector  may,  when  he  deems  fit,  order  that  certain  opera- 
tions shall  be  carried  out  under  agents  directly  under  his  control. 

Under  the  law  of  1836,  the  appointment  of  inspectors  of  all 
grades  lay  with  the  prefect,  who  might,  if  he  so  chose,  transfer  the 
control  of  the  roads  to  the  government  corps  of  engineers.  This 
right  of  option  was  taken  from  the  prefect  by  the  law  of  I860, 
which  included  among  the  duties  and  privileges  of  the  Council 
General  of  the  department  the  right  to  designate  to  what  parties 
should  be  confided  the  execution  of  work  upon  vicinal  roads.  The 
laws  of  1871  confirmed  this  right  and  extended  it  to  departmental 
roads,  so  that  to-day  the  nomination,  organization,  and  control  of 
the  staff  in  charge  of  department  roads  of  all  classes  is  the  exclusive 
right  of  the  prefectural  authority,  without  restriction. 

The  inspectors  are  divided,  ordinarily,  into  inspector-in-chief, 
inspectors  of  arrondissements,  and  inspectors  of  cantons.  They 
shall  be  French  citizens  and  must  be  at  least  21  years  of  age. 

The  law  of  1836  prescribes  that  in  each  department  there  shall 
be  a  commissioner  whose  duty  it  shall  be  to  examine  candidates  for 
the  position;  and  when  a  vacancy  occurs,  it  is  the  duty  of  the  pre- 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.      613 

feet  to  announce  the  date  of  such  examinations  in  his  department, 
and  send  this  notice  to  the  prefects  of  adjoining  departments.  The 
Minister  of  the  Interior  is  also  notified  of  all  such  vacancies  and 
changes. 

The  duties  of  the  inspectors  employed  on  the  vicinal  roads  are 
to  study  the  projects,  arrange  the  plans,  estimate  the  cost,  and 
watch  the  execution  of  all  road  work,  under  the  authority  of  the 
prefects  and  the  mayors.  Their  pay  is  fixed  by  the  Council  Gen- 
eral; and  they  are  never  to  be  remunerated  by  a  percentage  on 
work  performed. 

The  Laborers. — The  workmen  for  all  main  department  high- 
ways and  roads  common  to  several  communes  are  appointed  by  the 
prefect.  The  mayors  of  the  communes  name  those  employed  on 
the  ordinary  vicinal  roads;  but  as  this  appointment  implies  a  fixed 
charge  upon  the  commune,  his  action  must  be  sanctioned  by  a  vote 
of  the  municipal  council. 

Day's  Work  of  Proprietors. — France  has  a  system  of  working 
out  road  taxes,  but  it  is  carried  out  as  follows :  For  work  of  this 
nature  two  periods  are  generally  fixed  in  each  year,  ranging  from 
one  month  to  six  weeks  in  length,  each.  The  mayors  of  the  com- 
munes fix  the  dates,  and  so  arrange  it  that  any  work  commenced 
can  be  finished  in  the  specified  time.  And  in  connection  with  the 
inspector  of  the  canton,  the  mayor  also  divides  the  workmen  among 
the  several  roads  and  fixes  the  hours  for  beginning  and  ending 
work  at  each  place.  Five  days  before  the  date  fixed  the  mayor 
sends  to  each  laborer  working  under  this  system  a  notice  requiring 
him  to  report  at  a  certain  day  and  hour,  upon  a  certain  road,  for 
such  work  as  may  be  there  assigned  to  him.  In  case  of  sickness 
the  laborer  must- make  this  fact  known  to  the  mayor  within  twenty- 
four  hours  after  receiving  his  notice;  and  while  the  mayor  may 
postpone  the  service  required,  this  cannot  be  extended  beyond  the 
current  year.  As  an  unnecessary  number  of  workmen  at  any  one 
place  leads  to  confusion  and  embarrassment,  it  is  the  duty  of  the 
mayor  to  detail  at  one  time  and  on  any  one  piece  of  work  only  a 
sufficient  number  of  laborers  to  best  accomplish  a  specified  task 
without  loss  of  time.  If  this  labor  is  to  be  expended  on  a  vicinal 
road  of  common  interest  to  several  communes,  the  prefect  of  the 
department  designates  the  time  and  location  of  such  work. 

Each  workman  under  this  system  carries  to  the  place  designated 


614  HIGHWAY    CONSTRUCTION. 

such  common  tools  as  the  mayor's  notice  may  direct.  Tools  with 
which  the  farmers  are  not  ordinarily  supplied  are  furnished  by 
each  commune  from  the  fund  appropriated  to  public  works.  All 
6easts  of  burden  must  be  harnessed,  and  all  vehicles  must  have  a 
driver,  and  the  time  of  this  driver  is  received  as  a  full  acquittance 
for  the  time  of  one  man.  Farmers  may  substitute  for  themselves, 
or  members  of  their  family,  other  men  hired  and  paid  for  by  them- 
selves. These  substitutes  must  be  able-bodied  men  not  less  than 
•18  nor  more  than  60  years  of  age. 

The  length  of  the  day's  work  is  fixed  in  each  department  by  a 
general  rule  issued  by  the  prefect,  and  it  varies  according  to  the 
seasons  of  the  year.  This  day's  work  cannot  be  divided,  but  must 
Tbe  furnished  entirely  by  the  laborer.  In  case  of  legitimate  inter- 
ruption by  reason  of  bad  weather,  the  laborers  are  bound  to  com- 
plete it  at  the  earliest  date  possible.  If  the  laborer  fails  to  report 
at  the  hour  indicated,  or  in  any  way  fails  to  complete  his  legal 
day's  work,  the  lost  time  must  be  paid  for  in  money,  and  this  fine 
can  be  legally  recovered  by  the  municipal  receiver  of  taxes. 

Works  carried  out  on  vicinal  roads  under  the  labor-tax  system 
are  under  the  direction  and  control  of  the  mayor  of  the  commune 
in  which  such  roads  lie.  This  functionary  is  assisted  by  the  in- 
spector in  organizing  his  force  and  commencing  work,  and  each 
day's  work  is  preceded  by  a  roll-call,  compared  with  the  list  fur- 
nished by  the  mayor.  If  any  laborer  breaks  any  of  the  rules  fixed 
for  the  conduct  of  the  work,  comes  unprovided  with  the. tools  called 
for  in  his  official  notice,  or  in  any  way  does  not  conscientiously  per- 
form the  duty  assigned  him,  he  can  be  sent  from  the  work,  and  the 
value  of  his  services,  or  the  proportionate  part  thereof,  collected  in 
money.  At  the  end  of  each  day's  work  the  superintendent  of  works 
credits  each  laborer  upon  his  official  notice  with  the  number  of  days 
and  class  of  work  done,  and  at  the  same  time  discharges  the  original 
requisition  for  labor.  After  the  work  is  completed  this  accredited 
notice  is  signed  by  the  mayor,  and  sent  by  him  to  the  municipal 
receiver,  and  the  latter  makes  the  proper  entry  upon  his  books  or 
register  of  prestataires. 

In  case  a  commune  neglects  or  refuses  to  vote  the  number  of 
days'  work  necessary  on  its  roads  in  the  proper  time  for  perform- 
ance, and  the  sub-prefect  advises  the  prefect  of  this  fact,  it  shall 
be  the  duty  of  the  latter  official  to  serve  a  special  notice  upon  the 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       615 

mayor  of  the  defaulting  commune  demanding  that  he  execute  the 
required  work  within  the  specified  time.  This  same  notice  also 
notifies  the  farmers  that  unless  the  work  is  well  done  in  the  time 
fixed,  its  value  will  be  required  from  them,  in  money.  This  notice 
must  be  made  public  by  the  mayor;  or  in  case  of  his  refusal  by  a 
special  agent  of  the  prefect.  All  work  of  this  character  is  done 
under  the  supervision  of  an  inspector  appointed  by  the  prefect  or 
sub-prefect,  and  the  certificate  of  execution  is  delivered  by  the 
mayor  on  the  certificate  of  this  inspector.  If  the  mayor  refuses 
to  do  this,  the  certificate  of  the  inspector  himself  is  valid. 

Task-work  by  Proprietors. — Task-work  has  certain  advantages 
over  work  by  the  day,  for  the  laborers  are  free  to  select  their  own 
time,  and  by  more  active  exertions  they  can  shorten  their  hours  of 
labor.  When  the  municipal  council  of  a  commune  has  arranged  a 
basis  upon  which  it  can  convert  day's  work  into  task-work,  and  this 
schedule  has  received  the  approval  of  the  prefect,  the  mayor  of  the 
commune  may  decide,  so  far  as  the  smaller  reads  are  concerned, 
whether  work  in  his  commune  shall  be  done  by  one  system  or  the 
other,  as  he  may  deem  best.  This  decision  is  binding  upon  all  the 
prestataires  who  have  declared  their  intention  of  working  out  their 
taxes.  The  prefect  of  the  department  may  in  a  similar  manner 
decide  as  to  the  execution  of  work  upon  the  main  highways  and 
roads  of  common  interest  to  several  communes. 

When  such  task-work  is  to  be  done,  the  requisition-  states  the 
class  and  amount  of  work  and  the  date  by  which  it  must  be  com- 
pleted. The  character  of  work  required  is  further  indicted  upon 
the  ground  by  the  inspector  of  the  canton,  and  it  is  carried  out 
under  his  direction.  The  party  assigned  to  a  task  is  responsible 
for  its  proper  execution ;  and  upon  the  receipt  of  the  measurement 
and  certificate  of  the  inspector  that  it  is  properly  done  and  within 
the  given  time,  the  mayor  accredits  the  farmer  with  his  task.  Work 
improperly  done  must  be  done  over  again,  and  within  a  time  fixed 
by  the  mayor. 

Contract  Work. — The  mayors,  with  the  authority  of  the  prefect 
for  vicinal  roads,  and  the  prefect  for  the  main  highways  and  smaller 
roads  common  to  several  communes,  may  let  by  contract  the  con- 
struction and  repair  of  these  roads,  But  under  the  law  of  1836, 
the  proprietors,  even  when  the  work  is  converted  into  tasks,  cannot 
be  credited  for  taxes  with  work  done  under  the  control  and  for  the 


HIGHWAY   CONSTRUCTION. 


account  of  a  contractor.  Nevertheless,  when  work  on  any  depart- 
ment road  is  let  by  contract,  the  conditions  of  the  contract  oblige 
the  contractor  to  receive  in  return  for  services  the  day  work  or 
tasks  of  the  proprietors  according  to  a  conversion  tariff  approved 
by  the  Council  General  of  the  department  in  the  first  case,  and  by 
the  municipal  council  with  the  approval  of  the  prefect  in  the  sec- 
ond case. 

In  cases  where  the  department  supplies  this  labor  in  lieu  of 
taxes  from  the  laborer  and  cash  paid  to  the  contract  or,  the  de- 
partment by  its  agents  makes  the  requisitions  and  superintends  the 
execution  exclusively;  the  contractors  having  nothing  to  do  with 
the  disposition  of  the  men.  But  if  the  prestataires  do  not  carry 
out  their  obligations,  the  contractors  may  call  upon  the  mayor  or 
the  inspectors  to  compel  the  fulfilment  of  these  obligations. 

Cash  Work.  —  In  theory  all  work  for  which  money  is  paid  should 
be  executed  under  a  public  contract.  Nevertheless,  with  the  au- 
thority of  the  prefect  certain  work  may  be  let  by  private  argree- 
ment  under  the  following  conditions  : 

(1)  For  work  or  supplies  when  the  value  does  not  exceed  $600. 

(2)  For  work  when  the  conditions  forbid  the  delay  of  a  public 
letting. 

(3)  That  which  by  its  nature  requires  special  skill  and  experi- 
ence on  the  part  of  the  contractor. 

(4)  That  which  cannot  be  let  by  contract  after  two  several 
attempts  to  do  so.     Work  may  also,  with  the  authority  of  the  pre- 
fect, be  economically  carried  out  either  directly  under  the  control 
of  the  inspectors,  or  by  way  of  indirect  taxes,  in  cases  of  urgency 
or  when  other  methods  of  execution  have  been  recognized  as  im- 
possible or  less  advantageous.     Under  these  conditions  the  work 
should,  if  possible,  be  accomplished  by  the  task  system. 

All  projects  must  be  approved  by  the  prefect,  and  all  specifi- 
cations for  work  must  contain  the  clause  that  the  contracts  arc 
subject  to  the  general  conditions  imposed  upon  contractors  for 
vicinal  roads  as  annexed  to  the  general  instructions  issued  on 
December  6,  1870. 

The  provisional  or  final  acceptance  of  work  performed  upon 
main  highways  or  roads  common  to  several  communes  lies  with  the 
inspector  of  the  arrondissement,  assisted  by  the  inspector  of  the 
canton,  and  made  in  the  presence  of  the  contractor.  The  accept- 


MAINTENANCE. — REPAIRING  ;     CLEANSING  ;     WATERING.       617 

ance  of  vicinal  roads  lies  with  the  mayor  in  the  presence  of  the 
inspector  of  the  canton,  two  members  of  the  municipal  council, 
and  the  contractor.  The  contractor  is  always  summoned  on  these 
occasions,  but  his  absence  is  no  obstacle  to  the  action  of  the  offi- 
cials. 

All  difficulties  arising  from  disagreement  as  to  work  performed 
on  vicinal  roads,  or  from  damage  caused  by  these  works,  and  not 
arising  from  a  material  expropriation  of  lands,  can  be  adjusted  by 
the  council  of  the  prefecture,  with  appeal  to  the  council  of  state. 

Commissioners  of  Supervision. — In  some  departments,  the  pre- 
fects have  thought  it  proper  to  delegate  a  portion  of  the  care  of 
inspection  required  by  the  many  details  of  work  on  vicinal  roads 
to  a  commission  appointed  by  the  prefect  and  made  up  from 
members  of  the  General  Council,  the  councils  of  the  arrondisse- 
ments,  the  mayors,  and  certain  proprietors  particularly  interested 
in  the  good  condition  of  the  roads.  Where  a  road  passes  through 
two  arrondissements  and  is  too  long  to  be  easily  watched  by  one 
commissioner,  it  may  be  divided,  and  its  several  parts  supervised 
by  distinct  commissioners.  Each  commission  names  its  own  presi- 
dent and  secretary  and  fixes  the  day  and  place  of  meeting.  When 
the  prefect  or  sub-prefect  attends  a  meeting,  he  is  the  president 
for  the  time  being. 

When  the  prefect  thinks  best,  these  commissioners  may  be  con- 
sulted upon  projects  recommended  by  the  inspectors  for  new 
works,  and  upon  a  basis  of  a  division  of  expenses  between  the 
communes.  They  may  also  designate  several  of  their  number  to 
take  part  in  the  acceptance  of  work  done  by  contract.  Within  the 
first  three  months  of  the  year,  these  commissioners  send  to  the  sub- 
prefects  their  observations  upon  the  state  of  the  roads  and  point 
out  the  localities  most  urgently  needing  repair.  In  this  report 
they  also  name  the  workmen  who  have  most  faithfully  performed 
their  duty,  as  well  as  those  who  have  been  careless  or  slow  in  the 
performance  of  their  work. 

The  Police  of  the  Roads. — No  one  without  previous  authority 
can  perform  any  act  upon  a  road  that  in  any  way  interferes  with  its 
function  as  a  public  way  or  interrupts  travel.  And  it  is  specially 
forbidden  to  make  any  trenches  or  openings ;  to  deposit  stones,  earth, 
or  rubbish  upon  it;  to  take  away  any  sand,  gravel,  or  other  material; 
to  spread  anything  over  the  road;  to  divert  water  channels  so  as 


(Jig  HIGHWAY    CONSTRUCTION. 


to  cause  washing  of  the  road;  to  interrupt  in  any  way  the  flow  of 
water  in  the  ditches,  even  temporarily;  to  construct  or  repair  any 
building,  wall,  etc.,  bordering  upon  the  road ;  to  open  ditches,  plant 
trees  or  hedges  along  said  road,  or  to  dig  wells  or  cisterns  nearer 
to  the  road  than  provided  in  the  regulations.  To  perform  any  of 
these  intended  acts,  authority  must  first  be  formally  requested. 
For  all  vicinal  roads  this  authority  is  granted  by  the  mayor  with 
the  advice  of  the  inspector;  and  in  no  case  can  the  mayors  give  a 
verbal  authorization.  For  main  highways  and  other  more  impor- 
tant roads  the  authority  comes  from  the  prefect,  upon  the  report  < 
of  the  inspectors,  or  from  the  subprefect  under  similar  advice. 
Every  authorization  expressly  reserves  the  rights  of  third  parties, 
and  stipulates  that  the  roads  must  be  restored  to  their  normal  good 
condition. 

Ditches  and  Slopes. — In  giving  to  the  department  commis- 
sioners or  to  the  Council  General  the  right  to  give  to  vicinal  roads 
the  necessary  width,  the  law  of  1871  accorded  them  the  right  to 
include  all  the  land  required  for  proper  ditches  and  slopes.  These 
ditches  must  be  cleaned  as  often  as  necessary,  and  the  expense  of 
so  doing  is  charged  to  the  commune;  the  ditches  being  a  legal 
part  of  the  road,  and  protected  against  encroachment  in  the  same 
manner  as  the  road  proper.  If  the  authorities  have  not  opened  a 
ditch  along  the  whole  length  of  a  road,  as  sometimes  happens,  the 
bordering  proprietors  may  do  so  by  first  having  the  lines  and  levels 
given  them  by  the  proper  parties;  without  this  authority  they  are 
expressly  forbidden  to  touch  the  ditches.  The  care  of  ditches 
opened  for  their  own  protection  and  convenience  lies  in  the  hands 
of  the  proprietors. 

Rural  Roads. — Outside  of  the  vicinal  roads  properly  so  called, 
there  are  in  all  communes  a  certain  number  of  minor  roads  or 
means  of  communication  which,  while  of  little  importance,  per- 
haps, must  yet  be  carefully  maintained,  as  they  may  lead  to  a 
public  fountain,  a  watering-place  for  cattle,  or  to  common  pasturage. 
Such  roads  are  termed  rural  roads  in  the  law  of  1839,  but  they  are 
really  public  roads  in  the  sense  that  their  use  is  open  to  all,  that 
they  cannot  be  claimed  as  private  property  by  the  owners  of 
adjoining  soil,  and  that  they  are  legally  under  the  care  of  the  pub- 
lic authorities  and  are  maintained  in  the  same  manner  as  are  other 
roads  of  the  commune. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.       619 

The  method  adopted  is  to  map  every  road  and  every  public  path 
in  the  commune,  and  expose  this  plan  for  one  month  at  the  office 
of  the  mayor  of  the  commune.  Any  objections  made  to  the  correct- 
ness of  the  plot  or  claims  of  private  ownership  oi  roads  shown  are 
submitted  to  the  municipal  council,  which  is  to  sift  out  those  having 
a  basis  of  fact.  And  this  same  official  body  renders  an  opinion  upon 
the  degree  of  utility  of  the  roads  shown,  and  the  possibility  of  sup- 
pressing certain  ones  so  that  the  soil  may  be  sold  for  the  benefit  of 
the  commune.  The  map  with  the  report  of  the  municipal  council 
is  then  submitted  to  the  prefect  of  the  department,  who  examines 
it  to  see  that  no  vicinal  roads  have  been  included  under  the  head 
of  "  rural."  The  opposition  to  the  official  dedication  of  a  certain 
road  may  be  founded  upon  a  claim  of  property,  or  upon  the  fact 
that  it  is  not  public.  The  property  claim  is  decided  in  the  courts 
of  justice;  the  second  case  must  be  decided  by  the  administrative 
power,  that  is,  the  prefect. 

When  a  minor  road  of  this  kind  is  definitely  classified  as  a 
"  rural  road  "  it  is  public  property,  and  the  administrative  author- 
ity itself  cannot  restrain  travel  on  it  except  in  case  of  absolute 
necessity.  If  a  commune  wishes  to  enlarge  such  a  road,  it  can  do 
so  only  by  an  amicable  agreement  with  the  owner  of  the  necessary 
land,  unless  the  prefect  officially  classes  it  among  the  vicinal  roads. 
If  a  rural  road  is  suppressed,  the  soil  can  be  sold  for  the  benefit  of 
the  commune;  but  in  such  case  the  proprietors  bordering  on  such 
a  road  can  either  demand  that  the  use  of  it  be  continued  to  them, 
or  that  the  commune  provide  some  other  passage  or  pay  them  an 
indemnity. 

868.  Street  Cleansing. — Although  circumstances  legitimately 
determine  the  intervals  at  which  streets  shall  be  cleaned,  neverthe- 
less clean,  well-swept  streets  not  only  add  materially  to  the  pros- 
perous appearance  of  a  town,  but  they  also  have  a  very  marked 
influence  upon  the  health  and  morals  of  its  inhabitants;  wet  and 
muddy,  badly-formed,  ill-drained  streets  cause  dampness  in  the 
subsoil  of  the  dwelling-houses  in  the  vicinity  and  a  humidity  of 
the  atmosphere,  both  of  which  tend  to  produce  a  low  standard  of 
health  in  their  neighborhood,  irrespective  of  the  wet  surface 
through  which  pedestrians  have  to  wade  whenever  they  are  obliged 
to  cross  such  streets. 


G20  HIGHWAY   CONSTRUCTION. 

Dusty  streets,  too,  are  very  injurious  from  the  gritty  silicate- 
loaded  air  arising  from  them.  Such  an  atmosphere  when  inhaled, 
is  known  to  produce  disease  of  the  lungs,  even  when  free  from  the 
dust  arising  from  horse-droppings  or  other  organic  impurities. 

869.  The  dirt-producing  causes  common  to  all  roadways  are : 

(1)  Detritus  produced  by  the  attrition  of  the  paving  material,, 
horseshoes,  wheel- tires,  and  shoe-leather.     This  .cause  cannot  be 
eliminated. 

(2)  The  horse-droppings,  which  add  an  offensive  element  to  the 
body  of  street  dirt,  are,  if  collected  at  once,  valuable  as  manure. 
This  is  done  by  the  street  orderly  boys  in  London.     If  properly 
cared  for,  it  would  undoubtedly  afford  an  income  greater  than  the 
cost  of  collecting  it. 

(3)  Dirt  forced  up   through  the  joints  of  block  pavements. 
Under  modern  specifications  the   joints  of   block  pavements   are 
intended  to  be  closed  with  a  water-proof  material.     This  of  course 
would  give  full  protection  against  this  source  of  dirt,  but  in  the 
majority  of  block  pavements  it  is  doubtful  if  this  requirement  is 
ever  faithfully  performed.     A  few  months  generally  suffices  to  dis- 
lodge the  imperfect  filling,  and  the  material  of  the  substratum 
quickly  shows  itself  on  the  surface  of  the  pavement. 

(4)  House  and  shop  refuse  carelessly  swept  into  the  streets  is  an 
ever-present  source  of  street  dirt.     London  imposes  and  enforces  a 
fine  of  not  less  than  $25  and  not  exceeding  $200  upon  any  person 
sweeping  or  throwing  any  refuse,  dirt,  ashes,  dust,  decayed  fruit,  or 
offensive  matters  of  any  kind  upon  the  foot  or  carriage  ways.     Also- 
any  person  refusing  to  have  the  dust  or  ashes  removed  by  the 
scavengers  or  obstructing  them  in  the  performance  of  their  duties 
is  liable  to  a  penalty  not  exceeding  $25.     Again,  the  method  of 
removing  house-refuse  is  a  prolific  source  of  street  dirt.     The  re- 
ceptacles containing  it  are  brought  out  and  are  placed  on  the  edge 
of  the  curb  long  before  the  cart  makes  its  appearance  or  can  be  rea- 
sonably expected  to  do  so. 

870.  The  result  of  these  receptacles,  filled  with  heterogeneous 
collections  of  house-refuse,  being  left  unprotected  in  the  public 
streets  is  that  their  contents  are  quickly  strewn  about  the  surface 
of  the  street,  by  their  being  upset  accidentally  or  purposely;  and 
the  appearance  of  the  street,  which  has  probably  been  carefully 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.      621 

swept  and  garnished  during  the  night  or  early  in  the  morning, 
quickly  assumes,  especially  in  a  high  wind,  a  very  offensive  char- 
acter, and  probably  has  to  be  re-swept  and  cleansed  before  the  ordi- 
nary traffic  of  the  day  commences. 

871.  With  good  pavements  the  amount  of  refuse  to  be  removed 
is  reduced  to  a  minimum.     With  pavements  the  wear  of  which 
is   practically  nothing,  the   dirt   consists  principally  of  manure, 
which  has  a  ready  sale.     The  reduction  in  the  amount  of  unsala- 
ble refuse  is  an  object  to  be  sought  for;  its  collection  and  dis- 
posal is  an  expensive  jtem.     This  reduction  can  only  be  effected  by 
the  adoption  of  impermeable  pavements. 

In  Berlin  and  Liverpool  the  average  quantity  of  refuse  col- 
lected by  sweeping  has  been  continuously  decreasing  in  spite  of 
increased  traffic  and  area,  this  reduction  being  due  to  good  pave- 
ments. 

872.  Composition   of  Street  Dust. — The  following  analysis  of 
street  dust  is  given  by  Mr.  H.  G.  Hanks,  State  Mineralogist  of  Cali- 
fornia.    The  samples,  examined  under  the  microscope,  contained 
Tegetable  fibre,  principally  horse-manure  and  the  decaying  debris 
•of  Oregon  pine  and  redwood  planking,  bits  of  coke  and  coal,  glass, 
liorse-hair,  quartz  sand,  some  blue  particles  the  nature  of  which 
•could  not  be  determined,  and  a  dark-colored,  finely-divided,  half- 
dried  mud  which  was  pleasant  neither  to  the  sense  of  sight  or  smell. 
A  portion  mixed  with  distilled  water  and  placed  in  a  bottle  swarmed 
with  life  in  forty-eight  hours. 

Professor  Tyndall  has  also  shown  that  dusty  air  is  alive  with 
the  germs  of  the  bacteria  of  putrefaction,  whilst  the  pure  fresh  air 
which  he  gathered  on  a  mountain  peak  in  the  Alps  is  devoid  of 
such  germs,  and  is  absolutely  powerless  to  produce  any  organisms. 
Persons  living  in  streets  that  are  improperly  swept  or  watered  are 
unable  to  open  doors  or  windows  with  impunity  by  reason  of  the 
dust. 

Dr.  Letherby,  in  1867,  analyzed  dry  mud  from  the  streets  of  the 
city  of  London — dried  by  exposure  for  many  hours  to  a  tempera- 
ture of  from  266  to  300  degrees  Fahr.  At  the  same  time  he  ana- 
lyzed, for  comparison,  well-dried,  fresh  horse-dung  and  common 
farm-yard  dung.  The  results  of  the  analyses  of  the  mud  from  stone 
pavements  are  given  in  Table  LXXXV. 


622 


HIGHWAY   CONSTRUCTION. 


TABLE  LXXXY. 

COMPOSITION    OP   MUD    FROM    STONE-PAVED    STREETS,   HORSE-DUNG  AND 
FARM-YARD  DUNG. 

(Dried  at  300  degrees  Fabr.) 


Constituents. 

FreshJIorse- 
dung. 
Per  ceut. 

Farm-yard 
Dung. 
Per  cent. 

Mud  from  Stone-paved  Streets. 

Maximum 
organic 
(dry  weather). 
Per  cent. 

Minimum 
organic 
(wet  weather). 
Per  cent. 

Average. 
Per  cent. 

82.7 
17.3 

69.9 
30.1 

58.2 
41.8 

20.5 
79.5 

47.2 

52.8 

Mineral 

100.0 

100.0 

100.0 

100.0 

100.0 

The  higher  proportion  of  mineral  matter  in  wet  weather  proves 
that  in  such  weather  the  abrasion  of  stone  and  iron  is  greatest. 
Dr.  Letherby  estimated  that  the  average  proportions  of  stone,  iron, 
and  dung  in  the  muds  were : 

Horse-dung 57  per  cent 

Abraded  stone 30 

Abraded  iron » 13 

100  per  cent 

The  mud  was  so  finely  comminuted  that  it  floated  freely  away 
in  a  stream  of  water. 

In  the  mud  of  wood  pavements,  the  proportion  of  organic 
matter  in  the  dried  mud  was  larger  than  in  the  mud  of  stone  pave- 
ments. It  amounted  to  about  60  per  cent. 

The  amount  of  moisture  in  the  street  mud  varied  according  to 
the  state  of  the  weather. 

Stone  Pavements.  Moisture. 

In  the  driest  weather rarely  less  than  35    per  cent 

In  ordinary  weather "        "      "     48£       " 

Inwetweather "        "      "  70  to  90   " 

873.  The  detritus  of  the  material  of  a  granite  pavement  con- 
stitutes but  a  very  small  proportion  of  the  total  quantity  of  mud- 


MAINTENANCE.- — KEPAIRING  ;    CLEANSING  ;    WATERING.       623 

forming  dust.  Colonel  Hay  wood  exemplified  this  proportion  in 
an  interesting  manner,  taking  the  instance  of  the  granite  pavement 
of  London  bridge, — 3-inch  Aberdeen  granite  sets, — which  was  re- 
moved in  1851,  after  having  been  down  nine  years.  The  average 
loss  of  granite  over  an  area  of  3950  square  yards,  he  estimated,  was 
equal  to  2  inches  of  vertical  wear.  The  total  volume  of  granite 
worn  away  was  therefore  about  219^  cubic  yards,  assuming  that 
the  surface  was  a  continuous  mass  of  granite,  though  there  was  of 
course  a  considerable  superficial  area  of  joints.  Assuming  that 
the  granite  worn  oif  was  reduced  to  the  state  of  fine  powder,  it 
was  increased  in  bulk  probably  one  haL,  and  its  volume  had  been 
(219^  X  H  —  )329|  cubic  yards.  Adding  5$  for  the  loss  upon 
stones  removed  and  replaced  from  time  to  time,  the  total  quantity 
worn  off  and  reduced  to  powder  and  carried  away,  mixed  with  the 
dust  of  the  street  and  mud,  would  only  have  amounted  to  345.7 
cubic  yards  for  nine  years,  equivalent  to  a  wear  of  .105  cubic  yard 
— about  a  tenth  of  a  cubic  yard — per  day.  Whereas  the  quantity  of 
dust  removed  daily  in  dry  calm  weather  was  from  3  to  3^  cubic 
yards — over  thirty  times  as  much  as  the  granite  detritus.  So  much 
for  horse-droppings  and  shoe-leather,  which  must  have  constituted 
twenty-nine  thirtieths  of  the  total  accumulation,  independent  of 
the  contributions  of  house-refuse,  in  the  inhabited  streets.  Table 
No.  LXXXVI  shows  the  number  of  cubic  yards  of  street-refuse 
collected  in  a  few  cities. 


TABLE  LXXXVI. 
AMOUNT  OF  REFUSE  COLLECTED  FBOM  CITY  STREETS. 


City. 

Street  Mileage. 

Refuse  removed. 
Cubic  yards. 

780 

180,000 

Boston            ....... 

73 

70  499 

365 

259,398 

Buffalo  

225 

100.000 

660 

150  000 

New  York  

341 

535,709 

Philadelphia.  ....         

700 

266  831 

125 

127,623 

440 

200  000 

624  HIGHWAY   CONSTRUCTION. 

874.   The  relative  amount  of   dirt  produced   by  the  different 
pavements,  if  swept  daily,  appears  to  be  about  as  follows  : 


Cubic  Yards  per  1000  Yards 
Pavement. 


.007  t 

o  .04 

Wood  (impervious  joints)  

.04 

.07 

.0? 

20 

.015 

.024 

"       (open  joints)  

.07 

.25 

.10 

35 

These  figures  are  only  approximations  and  will  vary  with  the 
amount  of  traffic,  state  of  the  weather,  and  character  of  the  pave- 
ment of  intersecting  streets :  if  these  are  productive  of  dirt,  a  large 
quantity  will  be  dragged  by  the  vehicles  on  to  the  good  pavement, 
which  is  thus  debited  with  a  large  quantity  of  material  which  does 
not  rightfully  belong  to  it. 

The  care  exercised  in  the  removal  of  the  ashes  and  garbage  by 
the  occupiers  of  the  buildings  on  the  street  will  also  influence  the 
amount  of  dirt  to  be  removed. 

875.  Methods  employed  for  Cleansing. 

(1)  By  hand  during  the  day. 

(2)  By  hand  during  the  night. 

(3)  By  hand  and  machinery  during  the  night,  supplemented 
by  a  street  orderly  or  patrol  system  during  the  day. 

Of  the  above  methods  each  locality  will  have  to  decide  upon 
the  one  which  is  best  suited  to  its  requirements.  For  large  cities 
the  third  method  is  the  most  suitable. 

876^  Systems  of  Executing  the  Work. 

(1)  By  contract;   the  contractor  furnishing  all  the  tools  and 
labor. 

(2)  By  contract  for  the  labor  only,  the  city  furnishing  the  tools 
and  machinery. 

(3)  By  contract  for  the  horses  and  removal  and  disposal  of 
the  refuse,  the  city  furnishing  the  labor  and  machinery. 

(4)  By  the  city,  with  its  own  staff  and  machinery. 
Cleansing  by  contract  has  generally  proved  unsatisfactory,  from 

the  difficulty  of  obtaining  a  proper  observance  of  the  terms  of  the 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.      625 


contract  by  the  contractor  and  his  employes,  and  it  has  been 
found  that  the  work  can  be  more  carefully  and  systematically 
carried  out  by  the  civic  authority  with  its  own  officers  and  staff. 
It  is,  perhaps,  true  that  the  work  may  be  done  under  the  contract 
system  at  less  actual  cost  to  the  taxpayers,  but  all  public  work 
should  be  done  in  the  best  manner  possible  irrespective  of  cost, 
thoroughly,  but  without  extravagance;  and  the  result  of  such  work, 
especially  where  it  affects  the  cleanliness  and  the  appearance  of 
a  town,  soon  fully  repays  any  moderate  extra  cost  that  may  thus 
have  been  incurred,  irrespective  of  the  enormous  benefit  that  is 
conferred  upon  any  community  by  the  reduction  of  disease  and 
the  death  rate  by  a  proper  attention  to  such  necessary  sanitary 
work. 

The  semi-military  organization  introduced  by  the  late  Col. 
Waring  in  the  street-cleaning  department  of  New  York  City  has 
proved  eminently  successful.  He  employed  as  superintendents 
men  especially  fitted  by  either  military  or  technical  training  to 
carry  out  the  duties  assigned  to  them;  he  organized  the  laborers 
into  a  brigade  of  self-respecting  and  efficient  workmen,  clothed 
them  with  a  conspicuous  white  uniform,  which  most  of  them  keep 
surprisingly  clean  in  spite  of  the  work  they  do.  The  men  are  in 
responsible  charge  of  work;  if  they  shirk  it,  the  fact  is  recorded 
against  them,  while  good  work  is  also  noticed  and  reported.  Each 
sweeper  is  furnished  with  a  small  wheeled  iron  framework,  to 
which  he  attaches  a  bag  of  coarse  cloth,  a  broom  with  a  scraper  on 
the  back,  a  watering-can,  a  short  shovel,  and  a  scraper  when  he  has 
asphalt  to  look  after;  with  these  tools  he  is  expected  to  keep  a 
definite  area  of  pavement  clean.  The  sweepings,  instead  of  being 
left  in  heaps  along  the 'gutter  to  be  blown  about  by  the  wind  and 
scattered  by  wagon-wheels,  are  shovelled  up  and  placed  in  the  bag 
carried  on  the  truck-frame;  when  one  bag  is  filled  it  is  tied  up  and 
placed  on  the  curb,  and  another  placed  in  position  on  the  truck- 
frame.  These  bags  are  collected  by  wagons. 

The  work  is  done  under  the  supervision  of  foremen,  inspectors, 
and  other  officers,  who  report  how  each  man  is  doing  his  duty.  In 
case  the  men  wish  to  make  complaints,  they  must  first  state  their  case 
to  a  committee  of  forty-one  drivers  and  sweepers;  if  the  committee 


626  HIGHWAY    CONSTRUCTION. 

cannot  decide  the  case,  it  goes  to  a  committee  of  five  drivers  and 
five  officers  of  the  department;  and  in  case  this  committee  does 
not  come  to  a  decision,  it  is  settled  b.y  the  Commissioner  of  Street 
Cleaning. 

877.  Cost  of  Cleaning.— The  average  cost  of  cleaning  the  dif- 
ferent pavements  appears  to  be  as  follows : 

Asphalt 003  cent  per  square  yard  per  cleaning 

Stone  block 005      "      "        "          "      " 

Wood 007      "      "        "         "      " 

Brick 0034    •«    «        "          "      " 

Broken  stone 0106    "      "        "         "      " 

The  average  cost  of  supervision  varies  from  .011  cent  to  34 
cents  per  mile. 

The  cost  per  mile  of  street  cleansed  varies  as  follows : 

Omaha,  Neb.   $16.00 

St.  Louis,  Mo 17.00 

Boston,  Mass 20.00 

San  Francisco,  Cal 20.75 

Brooklyn,  N.  Y 22.75 

Cleveland,  Ohio 22.90  to  70.00 

The  amount  annually  expended  per  head  of  population  in 
street  cleaning  is  shown  in  the  following  table.  It  varies  from  5 
cents  in  Buffalo  and  8  cents  in  Chicago  to  71  cents  in  New  York 
and  92  cents  in  Cincinnati. 

The  average  of  eleven  bids  for  street  cleaning  recently  received 
in  Buffalo,  N.  Y.,  was  for  asphalt  37  cents  per  10,000  square  feet 
per  cleaning,  for  stone  block  55  cents  per  10,000  square  feet  per 
cleaning. 


MAINTENANCE. — REPAIRING  ;   CLEANSING  ;   WATERING.        627 

TABLE   LXXXVII. 

AVERAGE  ANNUAL  COST  PER  HEAD  OP  POPULATION  FOR  STREET 
MAINTENANCE. 


Cities. 


Average  Cost  per  Head  of  Population. 


Construction  and 
Repairs  of  Streets. 


Street  Cleaning. 


Baltimore,  Md $0.28 

Boston,  Mass 1.84 

Brooklyn,  N.  Y 0 .49 

Cambridge,  Mass 0. 64 

Camden,  N.  J 0.38 

Canton,  Ohio 1 .22 

Chicago,  111 3.18 

Cincinnati,  Ohio 2.88 

Cleveland,  Ohio 1.34 

Dallas,  Texas 0.47 

Davenport,  Iowa 1.12 

Detroit,  Mich 1 . 63 

Duluth,  Minn 15.00 

Elmira,  N.  Y 0.40 

Evansville.  Ind 0.66 

Fall  River,  Mass 0.89 

Hartford,  Conn 0.88 

Hobokeu,  N.  J 0.46 

Lacrosse,  Wis 0.81 

Lawrence.  Mass 0.74 

Lowell.  Mass 1.27 

Lynn,  Mass 0. 72 

Minneapolis,  Minn 1.21 

Nashville,  Teim 1.71 

Newark,  N.  J 0.11 

New  Haven,  Conn 1.68 

New  Orleans,  La 0.14 

Newport.  Ky 0.60 

New  York,  N.  Y 0.68 

Omaha,  Neb 4.15 

Philadelphia,  Pa 0.61 

Rochester,  N.  Y 1.06 

Rockford,  111 0.51 

St.  Louis,  Mo 1 . 85 

St.  Paul,  Minn.   5.69 

San  Francisco,  Cal 3.21 

Sioux  City,  Iowa 20.05 

Springfield,  Mass 

Taunton,  Mass 1.41 

Toledo,  Ohio 4.03 

Trenton,  N.  J 0.17 

Washington,  D.  C 2.50 

Worcester,  Mass 1.65 

New  York  (1896) 

Columbus  (1897) 


$0.25 
0.30 
0.20 
0.36 
0.19 

oios 

0.62 
0.19 

6!l9 
0.16 
0.15 
0.07 
0.15 


0.05 

6!  67 

6  '.18 


0.16 
0.06 
0.10 
0.16 
0.71 
0.16 
0.27 
0.15 
0.08 
0.28 
0.28 
0.20 
0.16 
0.28 


0.03 
0.31 
0.08 
1.29 
0.16 


628  HIGHWAY    CONSTRUCTION. 

878.  The  method  of  cleaning  employed  in  Berlin,  which  is  said 
to  be  the  cleanest  city  in  Europe,  is  as  follows : 

The  men  are  city  employes. 

The  sweeping-machines  are  city  property,  but  the  horses  are 
hired  by  contract. 

The  removal  of  sweepings  is  also  done  by  contract;  the  con- 
tractors for  this  work  being  obliged  to  maintain  suitable  dumping- 
places,  in  return  for  which  they  receive  for  their  free  use  the 
street  sweepings.  These  sweepings  are  of  some  value,  the  con- 
tractors often  realizing  over  $20,000  per  annum  from  them. 

The  contractors  are  bound  under  all  circumstances  to  supply 
enough  wagons  to  remove  each  day  all  street  waste.  The  number 
of  wagons  required  varies  with  the  weather.  In  dry  weather  often 
hardly  half  so  many  wagons  are  needed  as  in  wet  weather.  They 
are  required  to  remove  the  rubbish  as  soon  as  it  is  swept  up,  and 
only  in  cases  of  bad  weather  are  the  sweepings  allowed  to  stand  more 
than  one  hour  before  being  carted  away.  If  these  regulations  are 
broken,  the  contractors  forfeit  a  certain  amount  to  the  city. 

The  streets  are  cleaned  during  the  night. 

The  number  of  men  employed  by  the  city  is  about  600,  and  the 
number  of  sweeping-machines  in  use  in  1889  was  42. 

The  area  cleaned  in  1889  was  3,361,312  square  yards. 

The  average  daily  amount  cleaned  by  each  man  was  5716 
square  yards. 

The  area  swept  by  a  machine  ranges  from  6545  square  yards  on 
bad  pavements  to  10,315  square  yards  per  hour  on  asphalt  pave- 
ment. 

The  total  expenses  of  the  street-cleaning  department  in  1888 
and  1889  were  $481,493.48,  made  up  of  the  following  items: 

Wages $193,261.44 

Uniforms 2,769.12 

Tools,  materials,  etc 44,819.76 

Carting  away. . .   182,487.12 

Sprinkling 53,110.56 

Depots  for  supplies 1,221.12 

Public  closets 1,279.44 

Miscellaneous 2,544.48 

$481,493.04 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATEEING.       629 


Of  this  sum  the  street-car  companies  paid  for  cleaning  and 
sprinkling  the  parts  of  the  street  occupied  by  their  tracks  the  sum 
of  $24,135.58. 

The  quantity  of  refuse  removed  from  the  streets  was  as  follows : 
In  1882-83,  95,493  wagon-loads;  in  1888-89,  97,969  wagon-loads. 
The  number  of  loads,  therefore,  varied  very  little  in  spite  of  the 
considerable  increase  of  area  cleaned.  In  fact  in  the  year  1888-89 
the  number  was  about  1 6,000  less  than  in  1878.  when  it  amounted 
to  113,994  wagon-loads.  This  was  due  to  the  constant  increase  of 
good,  impervious  pavements. 

The  wages  of  the  laborers  employed  in  the  street-cleaning 
department  vary  between  36  and  83  cents  per  day,  in  addition  to 
which  they  receive  uniforms  free.  The  salaries  of  inspectors  range 
from  $357  to  $636  per  year;  they  also  receive  their  uniforms  free. 

New  employes  after  1-j-  years  service  are  advanced  to  a  higher 
grade. 

The  men  are  paid  for  Sundays  and  holidays,  and  in  case  of 
sickness  receive  half-pay.  Old  workmen  are  pensioned  after  10  to 
15  years"  service  at  $100  per  year,  and  for  30  years  or  more  $150. 
With  relative  allowance  between,  the  number  of  pensioners  in  1889 
was  11.  Assistance  is  also  rendered  to  sick  employes.  In  1889 
about  $100  was  expended  for  this  purpose. 

879.  In  Paris  street  sweeping  is  performed  by  2200  men,  950 
women,  and  30  boys.  They  begin  work  at  3  A.M.  in  the  summer 
and  at  4  A.M.  in  the  winter  and  continue  without  interruption  till 
11,  when  the  work  for  women  ceases;  the  men  continue  for  10 
hours  and  are  paid  by  the  day  from  65  to  74  cents.  The  women 
are  paid  6  cents  per  hour  and  cannot  earn  more  than  45  cents  a 
day.  All  are  obliged  to  provide  their  own  brooms.  The  roadmen 
in  charge  of  the  sweepers  are  paid  from  $21  to  $25  a  month. 
Those  receiving  the  lower  salaries  are  obliged  each  month  to  con- 
tribute the  odd  dollar  to  a  reserve  fund  that  is  deposited  to  the 
credit  of  each  workman  until  he  quits  his  employment.  The  plant 
consists  of  upwards  of  200  mechanical  sweepers. 

The  amount  of  refuse  removed  daily  averages  2300  cubic  yards 
and  requires  the  daily  use  of  520  carts  and  980  horses.  The  refuse 
is  disposed  of  by  public  tender  to  contractors  for  a  term  of  four 
years. 


630  HIGHWAY    CONSTRUCTION. 

880.  The  cleansing  of  the  city  of  London  is  carried  out  under 
the  department  of  the  commissioners  of  sewers.     The  force  em- 
ployed consists  of   about   500   men,  women,  and  children.     The 
work  begins  at  8  P.M.  and   is   concluded   at   9  A.M.     The  street 
orderly  boys  begin  work  at  7.30  A.M.     They  number  about  150, 
and  their  duty  is  to  remove  every  particle  of  dirt,  especially  horse- 
droppings,  in  the  area  assigned  to  them  before  it  has  been  ground 
by  the  wheels.     Bins  at  the  street  curb  receive  the  gatherings.     Not 
only  the  more  important  streets,  but  minor  ones,  courts  and  alleys, 
are  looked  after  by  the  orderly  boys.     These  boys  are  lodged  and 
fed  by  the  city,  a  certain  deduction  for  the  purpose  being  made 
from  their  wages.     As  they  reach  manhood  they  are  promoted  to 
other  positions,  and  when  they  attain  old  age,  after  faithful  service, 
they  are  pensioned. 

The  courts  and  alleys  inhabited  by  the  poorer  classes  are 
cleaned  daily,  and  from  May  to  October  are  washed  with  jet  and 
hose  usually  twice  a  week. 

881.  Baltimore,    Md.— Population,    443,547.      Street    mileage 
cleaned    (1891),   780.     Total   expenses   of   street-cleaning  depart- 
ment,  $283,070.54. 

Distribution  of  expenses : 

Collecting  garbage $139,062.16 

Cleaning  streets  and  removing  dirt .. . . . 118,423.00 

Dumps 4,689.40 

Tools 2,404.50 

Superintendence 9,991.48 

Removing  garbage  from  city  (contract) 8,500.00 

$283,070.54 

The  equipment  consists  of  150  garbage  carts,  61  street-dirt 
carts,  136  scrapers  and  sweepers.  Work  executed  by  city  employes. 
The  wages  paid  range  from  $10  to  $18  per  week.  The  sale  of 
street  dirt  and  refuse  realized  $912.76. 

882.  Boston. — Henry   B.   Wood,   Executive    Engineer   of   the 
street  commissioners  of  the  city  of  Boston,  in  a  recent  communica- 
tion   to    the    daily  press  says:    That  modern    hygiene    calls    for 
constant  attention  to  the  immediate  removal  of  all  kinds  of  street 
refuse  from  public  highways  and  places  before  fermentation  takes 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;    WATERING.        6ol 

place,  or  disease-laden  gases  or  dust,  particles  emanating  therefrom 
can  be  disseminated.  A  mere  occasional  attempt  to  clear  up  what 
street  litter  we  cannot  climb  over  is  not  sufficient ;  indeed,  the  pave- 
ment must  now  be  swept  so  clean  that  it  is  passable  at  any  point 
for  pedestrians.  He  continues : 

"  The  number  of  miles  of  streets  cleaned  is  7273.24,  at  an  average 
cost  of  less  than  $20  per  mile,  and  the  number  of  loads  of  street  dirt 
removed  is  77,000.  The  entire  force  of  men  employed  has  been 
about  300.  Some  streets  have  been  swept  every  day,  in  sweeping 
weather;  some  three  times  a  week.  Each  day's  work  has  been  so 
assigned  that  the  computed  area  covered  per  week  has  been  figured 
up  to  about  590,000  square  yards  to  a  district. 

"  For  a  paved  district  of  said  area  a  good  working  gang  is  com- 
posed of  one  foreman,  one  sub-foreman,  two  sweeping-machine 
•drivers,  two  water-cart  drivers,  sixteen  sweepers,  six  teamsters,  six 
helpers,  and  one  dump  inspector,  allowing  a  trifle  over  one  sweeper 
to  a  mile  of  gutter-stroke.  Such  a  force  costs  about  $23,000  for  a 
full  year.  Eighty-one  per  cent  of  the  streets  are  either  gravel  or 
macadam,  and  the  cost  of  cleaning  averages  about  $65  per  mile  for 
each  cleaning. 

"  The  introduction  of  the  push-cart  patrol  system  as  an  important 
adjunct  to  the  regular  street-sweeping  force  has  found  approval 
in  the  tidy  appearance  of  the  business  thoroughfares.  It  is 
found  that,  even  after  a  street  has  been  once  thoroughly  swept,  in 
less  than  two  hours'  time  the  sweeping  of  the  sidewalks  and  the 
throwing  away  of  waste  material  into  the  street  will  so  disfigure  its 
surface  that  it  appears  as  though  the  street-cleaning  force  had 
neglected  it  in  its  daily  rounds.  To  obviate  this  difficulty  the 
push-cart  patrol  comes  in,  collecting  and  removing  this  refuse 
matter  continually  throughout  the  day." 

In  1894  the  average  force  employed  was  303  men,  using  3  three- 
horse  machines,  19  double  and  21  single  sweeping-machines,  11 
water-carts,  90  street-carts,  100  horses,  14  asphalt-scrapers,  and 
about  33  extra  teams.  The  number  of  cart-loads  of  sweepings 
removed  was  95,478,  of  which  30,766  loads  were  dumped  at  sea; 
10,433  miles  of  streets  were  cleaned  and  2176  miles  of  paved  gut- 
ters on  macadamized  streets.  The  average  cost  per  mile,  including 
supervision,  labor,  yard  and  stable  expenses,  was  $15.61.  The  gross 
expenditure  divided  by  the  total  mileage  of  streets  in  the  city  shows 


632  HIGHWAY   CONSTRUCTION. 

that  the  cost  per  mile  per  season  was  $679.  The  operation  of  the 
push-cart  patrol  system  was  considered  most  satisfactory,  and  an 
extension  of  their  routes  is  thought  advisable.  They  alone  took  np 
50,280  barrel  loads  during  the  year.  The  cost  of  snow  removal 
during  the  year  was  $78,382. 

883.  Brooklyn,  N.   Y.— Population,  806,343.      Street  -mileage 
cleaned,  380.      Expenses  of  street- cleaning  department,  $239,875; 
supervision,  $36,000.      Work  done  by   contract.      Cost  per   mile, 
$22.75 ;  cost  per  capita,  30  cents. 

884.  Cleveland,  Ohio. — Population,  261,456.      Street  mileage 
cleaned,   680.      Expenses  of  cleaning   department   (1891),  $116,- 
099.51.     Work   done   by  contract.     Dry-weather  cleaning,  $22.90 
per   mile;  spring  cleaning  and   scraping,   $45.80   per   mile;   wet- 
weather  cleaning,  $70  per  mile.     Cost  per  capita,  42  cents. 

885.  Detroit  Mich. — The  streets  are  cleaned  when  and  as  often 
as  necessary.     The  work  is  done  by  day's  labor,  with  the  aid  of 
sweeping-machines.       This  work  is  principally  performed  by  aged 
persons  who  cannot  do  a  full  day's  labor  and  cannot  obtain  work 
elsewhere.     The  purpose  in  employing  labor  of  this  character  is  to 
preserve  the  independence  of  the  men  and  keep  them  from  becom- 
ing paupers.     Eight  hours  constitutes  a  day's  work,  and  $1.50  per 
day  is  paid.     The  hours  and  per  diem  allowance  are  fixed  by  the 
common  council. 

886.  In   New   York  the  street  cleaning  is   executed  by    the 
municipal  authority  under  the  direction  of  a  special  bureau,  part 
of  the  labor  being  furnished  by  men  in  its  employ  and  part  by  con- 
tract ;  the  carts  are  also  furnished  by  contract. 

The  total  number  of  men  employed  ranges  from  1500  to  2000, 
and  the  number  of  carts  is  between  300  and  400.  The  amount  of 
sweeping  collected  per  annum  is  about  550,000  cubic  yards.  The 
number  of  sweeping-machines  employed  is  about  60.  The  number 
of  miles  of  street  swept  each  day  is  about  *60,  tri-weekly  about 
200,  and  bi-weekly  about  70.  The  refuse  is  deposited  at  sea,  and  it 
costs  18  cents  per  cubic  yard  to  place  it  on  the  scows. 

The  cost  of  cleaning  the  above  street  mileage,  equal  to  an  area 
of  about  314,179,328  square  yards,  is  about  $1,279,647  per  annum. 

887.  Philadelphia,  Pa.— Population,  1,046,252.     Street  mileage 
cleaned,  756.     Work  done  by  contract.     Expense  of  street-cleaning 
department,  $552,000;  supervision,  $11,920.      Ashes  are  removed 


MAINTENANCE.— REPAIRING  ;    CLEANSING  ;    WATERING.        633 


weekly,  garbage  daily.  Amount  of  refuse  removed  in  1891:  garb- 
age, 84,065  loads;  street  dirt,  290,680  loads;  ashes,  573,999  loads; 
dead  animals,  14,795.  Number  of  men  employed,  400;  number  of 
machines,  17.  The  average  number  of  miles  cleaned  per  man  was 
118. 

888.  St.  Louis,  Mo. — Streets  paved  with  granite  and  wood  swept 
by  contract  at  50  cents  per  10,000  square  feet  per  sweep.     Asphalt 
pavements,  39  cents  per  10,000  square  feet  per  sweep.     The  mac- 
adam  and  Telford  cleaned  by  hand  labor,  under  the  supervision 
of  the  street  department. 

889.  St.    Paul,    Minn. — Population,    133,156.     Street    mileago 
cleaned,  349. 

Total  cost  of  cleaning  by  city  force  in  1891 : 


Labor. 

Unpaved  streets $35,470.11 

Paved  streets 20,296.27 


Materials. 

$119.11 

1,121.32 


Total , $55,766.38    $1,240.43 

Cost  of  cleaning  30,000  square  yards  of  asphalt  pavement  by 
hand  under  contract,  $49.75  per  week. 

Paved  streets  are  scraped  with  hoes  in  the  spring  at  a  cost  of 
about  $35  per  mile,  and  are  afterwards  kept  clean  with  sweeping- 
machines  at  a  cost  of  about  $9  per  mile. 

890.  Washington,  D.  C.— The  cleaning  of  the  streets  is  at  pres- 
ent performed  by  contract,  the  rate  in  1899  being  23|  cts.  for 
hand  and  21 J  cts.  for  machine  per  1000  square  yards  for  each 
sweeping.  The  improved  alleys  are  cleaned  under  another  contract 
(1899)  at  39  cts.  The  remainder  of  the  work  is  done  by  hired  labor, 
supplemented  to  some  extent  by  men  from  the  District  workhouse. 
The  extent  of  streets  swept  by  the  contractor  is  3,102,026  square 
yards,  equal  to  126.37  miles. 

The  remaining  streets  within  the  city,  which  are  cleaned  by 
hired  labor  and  the  chain-gangs,  are  as  follows : 


Pavement. 

Square  yards. 

Length,  miles. 

270,320 

8.0 

591,418 

29.4 

861,738 

37.4 

1,272,695 

71.9 

634  HIGHWAY   CONSTRUCTION". 

The  contractor  uses  ten  four-horse  sweepers,  five  of  the  Wright 
and  five  of  the  Filbert  pattern.  The  sweeping  is  done  by  night, 
except  when  the  contrary  is  specifically  authorized. 

The  amount  of  material  removed  from  the  streets  averages  1-J- 
cubic  yards  per  sweeping  to  every  3000  square  yards  of  area  swept. 
Before  sweeping  the  route  is  sprinkled  by  the  contractor  at  his  own 
expense.  The  average  force  employed  by  the  contractor,  besides 
the  10  large  sweepers,  consists  of  4  sprinkling-carts,  from  40  to  50 
broom,  hoe,  and  shovel  men,  and  between  30  and  35  carts.  The 
maximum  force  here  named  will  clean  900,000  square  yards  of 
pavement  in  12  hours.  The  total  cost  of  the  cleaning  is  divided 
between  the  government  and  the  city,  the  cost  per  capita  being 
about  21  cents  per  year. 

891.  Street  Orderly  or  Patrol  System. — This  system  comprises  a 
staff  of  men  or  boys  usually  the  latter,  equipped  with  a  bag  or  scoop 
and  a  brush.  Each  boy  is  assigned  to  a  definite  area,  from  which 
he  removes  all  horse-droppings  and  refuse  as  it  falls  and  before  it 
has  time  to  be  ground  up  by  the  wheels.  The  pans  are  of  sheet-iron 
formed  as  shown  in  Fig.  281.  The  bags  are  of  canvas  and  are  shaped 
like  an  old-fashioned  carpet-bag;  one  of  the  lips  is  provided  with  a 
metal  edge  over  which  the  refuse  is  swept.  The  brush  is  generally 
made  of  a  bundle  of  birch  twigs. 

The  refuse  so  collected  is  disposed  of  in  different  ways. 

In  London  cast-iron  boxes  are  fixed  at  the  curb  into  which  the 
boys  empty  the  scoops  when  filled;  the  receptacles  are  in  turn 
emptied  by  shovels  into  carts  at  stated  intervals. 

The  bag  is  claimed  to  be  better  than  the  scoop;  it  holds  more 
than  the  scoop,  and  therefore  requires  less  running  to  the  re- 
ceptacles to  be  emptied,  and  it  covers  up  the  refuse ;  but  the  empty- 
ing process  is  always  troublesome  and  can  hardly  be  conducted 
without  considerable  dirt  being  scattered  in  emptying. 

In  Paris  the  refuse  is  collected  in  a  similar  manner,  but  instead 
of  sidewalk  receptacles  they  have  a  light  wrought-iron  vehicle  pro- 
portioned to  carry  four  full  bags,  two  inside  and  two  suspended 
from  hooks  on  the  outside.  This  system  fills  the  bags  at  once,  allows 
them  to  be  stored  without  offence  or  dirt  anywhere,  and  the  final 
removal  is  expeditious  and  cleanly.  Fig.  278  shows  the  hand- 
cart used  by  the  street  patrol  in  New  York  and  several  American 
cities. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;   WATERING.       635 

892.  Street  cleansing  is  effected  either  by  hand  sweeping  and 
scraping  or  by  mechanical   sweepers.     As  to  which  is  the  most 
economical,  much  depends  upon  the  value  of  labor,  and  also  upon 
the  condition  of  the  roads  to  be  dealt  with.    On  pavements  covered 
with  ruts  and  depressions  machine  brooms  are  not  effective,  but  in 
point  of  time  and  as  a  general  rule  the  value  of  a  horse  rotary- 
brush  sweeping-machine  is  undoubted;  the  only  time  at  which  such 
n  machine  fails  to  do  effective  work  is  on  the  occasions  when  the 
mud  to  be  removed  (owing  to  a  peculiar  condition  of  the  atmos- 
phere) has  attained  a  semi-solidity,  and  is  of  a  stiff  and  sticky  con- 
sistency, when  it  either  adheres  to  and  clogs  the  brushes  of  the 
machine,  or  is  flattened  by  them  onto  the  road  instead  of  being  re- 
moved.    In  such  a  condition  of  the  street  the  scraping-machine 
must  be  employed,  but  care  must  be  exercised  in  its  use,  as  there 
is  always  danger  of  injuring  the  pavement. 

893.  Cost  of  Street  Sweeping. — City  Engineer  Rundlett  has  kept 
•a  careful  account  of  sweeping  the  paved  streets  of  St.  Paul,  by  hand 
and  by  machines.     The  average  cost  by  hand  in  May  was  $25.00; 
June,  $20.18;    July,   $18.57.     Total   average   per  mile   by   hand, 
$20.00;  by  machine,  $9.24. 

In  cleaning  the  streets  of  St.  Louis  the  bids  for  cleaning  as- 
phalt pavements  are  25  per  cent  below  those  based  on  granite 
*)lock. 

In  Washington  the  street  cleaning  in  1899  cost  23|  cts.  for  hand, 
21-j-  cts.  for  machine,  and  39  cts.  for  alleys  per  thousand  yards, 
cleaned  once. 

894.  The  amount  of  surface  which  one  man  can  sweep  per  hour 
depends  upon  the  condition  of  the  pavement,  dry,  wet,  or  muddy. 
The  following  figures  are  approximate : 

Asphalt,  dry 1200  square  yards  per  hour. 

wet  and  muddy 1000      " 

Granite  block,  dry ,....1000      " 

"          "        wet  and  muddy 750      " 

Macadam,  dry 700 

"          wet  and  muddy 350 

895.  The  amount  of  surface  cleaned  by  a  mechanical  sweeper 
will  depend  upon  the  width  of  the  machine  broom,  the  power  of 
the  horses,  gradient,  and  condition  of  the  surface.     The  wider  the 
stioke  of  the  broom  the  less  will  be  the  cost  of  sweeping.    As  the 


(536  HIGHWAY    CONSTRUCTION. 

width  of  stroke  differs  in  different  machines,  the  area  swept  by  each 
in  a  given  time  will  vary  with  that  width. 

The  average  speed  of  the  mechanical  sweepers  is  one  and  a 
half  miles  per  hour. 

896.  The  cost  of  operating  a  machine  sweeper  is  about  50  cents 
per  hour.     With  a  machine   having  a  stroke  of  5^  feet  it  will  re- 
quire six  strokes  of  the  machine  to  sweep  a  30-foot  roadway ;  there- 
fore, to  clean  one  mile  of  roadway   30  feet  wide,  such  a  machine 

I  must  travel  six  miles,  and  will  require  about  four  hours  and,  at  50 
cents  an  hour,  cost  $2.00.  With  a  machine  having  a  stroke  of  8  feet, 
but  four  miles'  travel  of  the  machine  will  be  required. 

897.  Brooms. — The  hand  brooms  used  are  made  of  steel  wire, 
rattan,  bass  and  birch.     As  the  strength  and  durability  of  these 
brooms  is  of  some  importance  as  affecting  the   ultimate   cost   01 
street  sweeping,  care  should  be  exercised  in  their  selection. 

Steel  wire  lasts  longer  than  any  other,  but  is  only  suitable  for 
block  pavements.  Bass  and  birch  are  weak  and  speedily  wear  out. 
Rattan  is  most  suitable  for  asphalt  and  Macadam  pavements. 
Rubber  squilgees  or  mops  are  most  efficient  for  cleansing  asphalt 
pavements. 

898.  Carts  and  Wagons. — The  carts  and  wagons  employed  in 
the  removal  of  street  dirt  should  be  provided  with  covers.     The 
employment  of  wooden  carts  for  this  work  is  not  economical;  the 
rough  usage  which  they  receive  renders  their  life  but  a  short  one,, 
and  they  are  constantly  requiring  repair.     Iron  or  steel  should  be 
substituted.     Such  carts  are  to  be  purchased  in  the  market  and 
have  many  points  to  recommend  them. 

899.  The  methods  employed  for  the  final  disposing  of  the  street 
refuse  are  many  and  varied.     In  the  seaboard  cities  and  those  situ- 
ated on  rivers  it  is  generally  placed  on  barges,  carried  to  sea  or 
other  deep  water  and  deposited.     In  others  it  is  used  for  filling  in 
low  lands  (a  practice  which  cannot  be  too  strongly  condemned).  In 
a  few  localities  it  is  destroyed  by  fire.     This  is  the  superior  method 
and  quite  successful,  and  is  gaining  in  favor  in  situations  where 
difficulties  are  encountered  in  disposing  of  the  refuse,  the  only  ob- 
jection raised  against  it  being  the  offensive  odor.     This  odor  is  not 
so  bad  as  people  imagine;  it  approximates  that  of  burning  leather 
and  can  be  entirely  avoided  by  suitable  devices  and  chimneys  of 
sufficient  height.     As  a  rule,  people  are  prejudiced  against  crema- 
tories being  located  near  their  residences. 


MAINTENANCE. — REPAIRING  ;    CLEANSING  ;   WATERING.       037 

The  cost  of  a  plant  for  a  town  having  a  population  of  100,000 
would  be  about  $100,000.  The  cost  of  cremating  the  refuse  ranges 
from  20  to  40  cents  per  ton,  depending  upon  the  amount  of  com- 
bustible the  refuse  contains. 

900.  Removal  of  Snow. — An  important  feature  of  maintenance 
is  that  involved  in  the  removal  of  snow.     Good  management  im- 
plies that  it  shall  be  speedily  removed  and  not  left  to  interrupt 
travel. 

901.  In  American  cities  no  provision  is  made  beforehand  for 
the  extra  assistance  required  for  its  removal,  and  all  that  can  be 
done  is  to  collect    as  many  teams  and    men    as   possible    at  the 
moment;  the  result  is  that  much  valuable  time  is  wasted  in  this 
operation.     In  European  cities,  this  extra  labor  is  engaged  in  ad- 
vance.    In  Paris  a  contract  is  made  each  year  with  the  general  om- 
nibus company  to  supply  carts  and  horses  at  any  time  needed.     In 
London  also,  contingent  contracts  provide  for  any  additional  num- 
ber of  teams  required  at  a  moment's  notice. 

902.  The  organization   and   arrangements  for  the  removal  of 
snow  in  the  cities  of  Milan  and  Turin,  Italy,  are  the  most  complete 
of  any  city,  and  a  description  of  their  methods  may  be  interest- 
ing. 

The  system  adopted  in  Milan  is  as  follows :  The  city  is  divided 
into  districts  of  varying  extent  according  to  their  importance;  each 
district  is  allotted  to  a  contractor,  who  has  to  find  the  carts,  horses, 
and  laborers,  while  the  city  furnishes  the  necessary  implements, 
spades,  shovels,  brooms,  scrapers,  barrows,  etc.,  with  proper  stipu- 
lations as  to  their  care.  The  contracts  are  made  annually,  and  gen- 
erally the  same  persons  are  anxious  to  secure  them.  The  form  of 
the  contract  is  rigid,  and  the  contractors,  who  are  drawn  from  the 
trades  most  affected  by  winter — paviors,  bricklayers,  masons,  quarry- 
men,  etc., — are  held  to  a  rigid  responsibility.  Payment  is  only 
made  for  work  which  is  well  done;  slovenly  and  careless  execution 
goes  for  nothing.  The  supervision  of  each  district  is  under  an  en- 
gineer aided  by  assistants  and  the  police. 

Payment  is  made  per  inch  depth  of  snow  fallen.  The  average 
depth  of  the  snowfall  in  each  district  is  determined  from  the  depth 
of  the  snow  caught  on  a  number  of  stone  posts  fixed  in  open  spaces 
and  clear  of  shelter  from  buildings.  Each  post  is  capped  with  a  flat 
slab  set  horizontally.  The  depth  of  the  snow  on  these  slabs  is  meas- 


638  HIGHWAY    CONSTRUCTION. 

ured  by  the  engineer  of  the  district  in  presence  of  two  of  the  con- 
tractors of  his  section. 

The  average  cost  of  removing  the  snow  per  inch  of  depth  per 
square  yard  is  .006  cent.  Ordinarily  the  removal  of  the  snow  from 
the  more  active  thoroughfares  is  finished  within  ten  hours  of  the 
cessation  of  the  storm,  and  from  the  rest  within  24  hours,  exclusive 
of  night. 

The  snow  is  dumped  into  the  navigable  canals  and  water-courses 
intersecting  the  city,  and  latterly  into  the  new  sewers  in  the  central 
portions  of  the  city,  which  are  promptly  flushed  whenever  it  snows* 

The  number  of  men  engaged  in  the  removal  of  snow  in  addition, 
to  the  regular  street-cleaning  force,  ranges  from  2000  to  3000y 
according  to  the  severity  of  the  storm.  The  implements  are  housed 
in  different  storehouses  throughout  the  city.  The  whole  expense 
of  removing  and  disposing  of  the  snow  during  the  remarkable 
winter  of  1874-75,  when  more  than  40  inches  of  snow  fell,  was  about 
$44,000.  In  the  case  of  each  storm  the  work  of  removal  was  done 
within  24  hours. 

903.  In  Turin  much  the  same  method  is  practised,  work  being 
paid  for  by  the  exact  measure  of  snow  fallen.     The  street-car  com- 
panies are  obliged  to  bear  their  share  of  the  expense,  paying  for  a 
width  of  9  feet  10  inches  for  single  and  18  feet  8  inches  for  double 
tracks. 

904.  Many  schemes  for  the  disposal  of  snow  have  been  experi- 
mented with,  such  as  dumping  it  into  the  sewers,  melting  it  by 
the  application  of  steam,  hot  air,  etc.,  as  also  with  salt ;  but  the  only 
successful  scheme  so  far  is  by  cartage,  depositing  it  in  adjacent 
streams,  or  where  this  is  objectionable,  as  in  the  case  of  navigable 
rivers,  it  may  be  heaped  up  in  vacant  lots  or  in  the  squares  and 
parks,  provided  no  damage  is  done  to  the  grass  or  paths. 

905.  Dumping  the  snow  down  the  manholes  into  the  sewers  has 
been  tried  in  London  and  other  cities,  but  has  generally  failed 
through  the  snow  consolidating.     An  experiment  with  this  method 
in  the  city  of  Cologne  gave  the  following  results.     A  number  of 
shafts  were  opened  into  the  crown  of  the  main  sewer  that  empties 
into  the  Rhine,  each  shaft  being  from  2  to  5  feet  square.     At  one 
of  these  places  the  sewer  was  of  oval  section,  6  feet  x  4  feet,  and 
the  fall  was  1 :  600.   It  was  possible  to  dump  the  snow  directly  from 
the  carts,  each  of  which  held  about  two  cubic  yards,  into  the  sewer 


MAINTENANCE. — REPAIRING;    CLEANSING;   WATERING.        639 


without  stopping  the  flow  there.  At  another  place  where  the 
sewer  was  4  feet  X  2.3  feet  and  the  same  fall  prevailed,  this  process 
was  not  possible  although  a  strong  stream  of  water  was  thrown  011 
the  mass  from  the  water  service-pipes.  The  large  mass  suddenly 
thrown  into  the  sewer  acted  as  a  dam  and  had  to  be  removed. 
But  at  this  same  shaft  when  the  same  amount  of  snow  was  regu- 
larly thrown  into  it  by  four  laborers  no  stoppages  occurred.  A  few 
hundred  feet  below  the  place  all  the  snow  was  found  to  be  melted. 
Several  hundred  loads  of  snow  were  removed  through  these  two 
shafts  alone  in  a  few  hours. 

The  cost  of  melting  snow  by  the  application  of  hot  air  or  steam 
far  exceeds  that  of  shovelling  and  carting  away. 

906.  In  order  to  grapple  with  this  question  of  the  removal  of 
snow  when  no  provision  has  been  made  beforehand,  the  following 
suggestions  may  be  of  use : 

"  It  is  useless  to  attempt  to  cart  it  away  while  falling,  but  try 
to  make  clear  crossings  for  the  foot-passengers  and  to  keep  the 
traffic  open.  If  there  should  be  a  high  wind  at  the  time,  and  the 
snow  drifts  in  consequence,  cut  through  the  drifts  so  as  to  allow 
the  vehicular  traffic  to  continue.  Directly  the  snow  ceases  to  fall 
put  on  all  available  hands  to  clear  the  channel-gutters  and  street- 
gratings,  in  preparation  for  a  sudden  thaw,  when,  if  these  precau- 
tions were  not  taken,  serious  flooding  and  great  damage  to  property 
might  ensue;  for  the  same  reason  cart  away  all  the  snow  you  can 
at  the  bottom  of  the  gradients  and  in  the  valleys,  and  also  from 
very  narrow  streets  and  passages,  etc.  In  the  wider  streets  use  the 
snow-plough,  or  with  gangs  of  men  (in  the  snow  season  there  is 
generally  plenty  of  labor  obtainable)  shovel  the  snow  into  a  long 
narrow  heap  on  each  side  of  the  street,  taking  care  to  leave  the 
channel  gutters  and  gratings  quite  clear,  and  a  sufficient  space 
between  the  heaps  for  at  least  two  lines  of  traffic.  Passages  must 
also  be  cut  at  frequent  intervals  through  the  heaps,  in  order  to 
allow  foot-passengers  to  cross  the  street,  and  also  to  let  the  water 
reach  the  channel-gutters  as  soon  as  the  snow  begins  to  melt." 

907.  With  regard  to  the  removal  of  snow  from  the  footpaths,  it 
is  highly  desirable  that  this  should  be  effected  by  the  occupiers  of 
the  premises  adjacent  to  the  street,  as  otherwise  it  adds  immensely 
to  the  work  of  the  local  authority.     The  following  interesting  re- 
marks by  the   superintendent  of  the  scavenging   department   of 
Liverpool  will  be  no  doubt  read  with  great  interest : 


640  HIGHWAY   CONSTRUCTION. 

"  The  only  way  to  compass  the  removal  of  snow  from  the  foot- 
walks  of  the  principal  thoroughfares  within  a  comparatively  short 
time  is  by  sprinkling  them  with  salt  such  as  is  commonly  used  for 
agricultural  purposes.  It  is  certain  that,  unaided  by  the  salt,  a 
sufficient  number  of  men  cannot  be  procured  for  the  emergency  of 
clearing  snow  from  the  footways  of  the  most  important  thorough- 
fares. It  has  been  stated  by  medical  authorities  that  the  applica- 
tion of  salt  to  snow  is  detrimental  to  the  health  of  people  who  have 
to  walk  through  the  'slush'  produced  by  the  mixture,  and  that  the 
excessive  cooling  of  the  air  surrounding  the  places  where  the  appli- 
cation has  been  made  is  injurious  to  delicate  persons.  It  therefore 
seems  that  the  application  of  salt  to  snow  should  not  be  undertaken 
during  the  daytime,  but  should  be  commenced  not  before  11  P.M., 
nor  continued  after  6  A.M.,  and  that  only  such  an  area  of  footwalks 
should  be  so  treated  on  any  one  night  as  the  available  staff  of  men 
can  clear  by  an  early  hour  the  following  morning. 

"  To  sweep  snow  from  the  footwalks  whilst  the  fall  of  snow 
continues,  and  especially  during  business  hours,  appears  to  be 
wasteful  and  futile,  and  to  apply  salt  during  the  same  periods  may 
be  held  to  be  injurious  to  health. 

"  That  the  snow  of  an  ordinary  fall  can  be  removed  from  the 
footwalks  by  an  application  of  salt  an  hour  or  so  before  they  are 
scraped  is  an  ascertained  fact,  except  at  least  when  a  moderately 
severe  frost  has  preceded,  accompanied,  or  followed  the  snowfall, 
or  when  the  snow  has  drifted  into  extensive  accumulations.  Were 
it  not  for  the  danger  to  health  by  excessive  cooling  of  the  air,  and 
for  the  expense  attending  the  operation,  all  the  impervious  pave- 
ments could  be  cleared  of  snow  (unless  the  fall  was  a  heavy  one)  in 
a  comparatively  short  time  by  a  liberal  application  of  salt  and  the 
employment  of  the  horse  sweeping-machines  as  soon  as  the  snow 
lias  become  sufficiently  softened  to  admit  of  their  use. 

In  Paris  the  use  of  salt  for  melting  the  snow  is  carried  to  a 
considerable  extent.  Pure  fine  salt  for  this  purpose  is  delivered  at 
the  railway  stations  at  about  $6  per  gross  ton — the  state  and  city 
taxes,  which  amount  to  $32,  being  remitted.  It  was  first  used  on  a 
large  scale  in  1880.  It  produces  a  dark-colored  slush  with  a  tempera- 
ture of  about  10°  F.,  which  will  not  freeze  unless  the  temperature 
falls  below  this  degree.  When  it  does  not  interfere  too  much  with 
traffic  in  the  streets  it  is  often  left  in  place  for  several  days,  because 


MAINTENANCE. — REPAIRING;    CLEANSING;    WATERING.        641 

it  does  not  freeze  and  is  to  a  considerable  extent  a  prevention  of 
slipping.  If  it  becomes  too  thick,  it  is  removed  with  scrapers  or 
with  sweeping-machines. 

The  action  of  the  salt  is  more  rapid  the  more  rapid  the'  traffic; 
on  streets  of  great  travel  the  snow  of  the  salted  surface  is  reduced 
to  mud  in  two  hours. 

No  account  is  taken  of  the  effect  of  the  salt  and  snow  mixture 
on  the  health  of  the  people. 

The  salt  is  spread  from  wheelbarrows  by  the  shovel,  and  does 
not  need  to  be  very  uniform.  If  the  snow  (packed)  is  six  or  eight 
inches  deep,  a  surface  layer  is  first  melted  and  removed,  and  the 
lower  layer  is  salted  in  turn. 

Amount  of  Salt  Required. — It  is  estimated  that  to  melt  packed 
snow  to  a  depth  of  1£  to  2  inches  about  5  ounces  of  salt  are  re- 
quired per  square  yard. 

The  application  of  salt  on  broken-stone  roads  in  winter  will  not 
prevent  the  freezing  of  the  ground,  but  will  increase  the  mud-pro- 
ducing action  of  the  water  formed  by  the  melted  snow,  thus  caus- 
ing their  condition  to  be  much  worse  than  if  the  snow  were  allowed 
to  remain  in  its  solid  form. 

In  the  United  States  the  bad  effect  upon  horses"  feet  of  the  cold 
produced  by  the  use  of  salt  has  been  the  cause  of  much  complaint, 
and  the  Society  for  the  Prevention  of  Cruelty  to  Animals  has  taken 
up  the  matter  of  regulating  its  use. 

A  mixture  of  salt  and  snow  produces  a  temperature  in  the 
mixture  of  0°  F. 

'Sea-water  sprinkled  on  snow  causes  the  latter  to  melt  rapidly. 
It  will  not  freeze  except  at  a  temperature  many  degrees  below  that 
required  to  freeze  fresh  water. 

908.  Weight  of  Snow. — Experiments  made  show  that  a  cubic 
yard  of  fresh-fallen  snow  may  weigh  as  much  as  814  pounds  or  as 
little  as  71,  or  a  range  of  from  2.63  pounds  to  30.14  pounds  per 
cubic  foot. 

"  Snow  readily  compresses  under  traffic,  and  when  removed 
in  carts  and  dumped  elsewhere  it  may  be  assumed  that  on  an 
average  four  cubic  yards  of  snow  measured  as  it  has  fallen  is  equal 
to  one  cubic  yard  when  placed  on  the  apparatus."  This  computa- 
tation,  however,  does  not  make  any  allowance  for  the  snow  thrown 


G42  HIGHWAY    CONSTRUCTION. 


from  off  the  roofs,  etc.,  and  it  of  course  greatly  consolidates  whilst 
travelling  in  the  cart. 

909.  The  removal  of  light  falls  of  snow  from  country  roads 
may  be  effected  by  the  ordinary  snow-plough  forming  it  into  a  long 
narrow  heap  on  each  side,  but  taking  care  to  leave  the  gutters  un- 
obstructed.    Heavy  drifts  must  be  cut  through  with  the  shovel. 

In  some  localities  it  may  not  be  desirable  to  remove  the  snow, 
sleighs  being  used  in  place  of  wagons.  In  such  cases  care  must  be 
taken  when  a  thaw  sets  in  to  have  ditches  and  water-courses  clear. 

910.  Street  Washing. — Cleansing  the  pavements  by  washing 
them  with  a  stream  of  water  from  the  fire-hydrants  is  practised  in 
both  Paris  and  London.     In  the  former  city  it  forms  part  of  the- 
daily  routine,  but  in  the  latter  it  is  only  used  periodically,  and  more 
especially  in  the  courts  and  alleys.     Disinfectants  are  also  used  in 
Paris  in  this  connection.     During  1890  this  method  was  experi- 
mented with  in  New  York.     The  results  were  not  satisfactory;  the 
muddy  water  collected  in  puddles  in  the  hollows  of  the  pavement, 
and  the  amount  of  mud  and  silt  carried  into  the  sewers  threatened 
to  soon  choke  them  up. 

This  method  is  specially  applicable  to  impervious  pavements, 
such  as  asphalt  and  stone  blocks  and  brick  with  water-proof  joints. 
Wood  pavements  when  they  become  covered  with  sticky  mud  are 
more  easily  cleansed  by  washing. 

In  washing  asphalt  pavements  sufficient  water  must  be  used  to 
convert  the  dust  and  dirt  into  a  fluid  mud;  if  a  quantity  insuffi- 
cient to  produce  this  result  is  applied,  the  dirt  is  converted  into  a 
pasty  condition,  with  the  result  that  the  surface  becomes  dangerous 
for  horses.  This  pasty  mud  is  also  difficult  to  remove  either  with 
brooms  or  other  practicable  appliances;  horse -manure  when  it  dries 
sticks  to  the  asphalt  and  cannot  be  removed  in  dry  weather  unless 
it  be  previously  soaked  and  scraped  off.  After  washing,  the  sludge 
formed  should  be  removed  by  the  use  of  rubber  squilgees;  their 
use  will  also  hasten  the  drying  of  the  surface. 

In  many  cities,  especially  such  as  suffer  from  periodical  droughts, 
objection  is  raised  to  the  large  quantity  of  water  required  for 
street  washing.  In  many  German  cities  this  objection  is  overcome 
by  scraping  the  asphalt  pavements  with  rubber  squilgees  while  they 
are  covered  with  the  water  from  the  spHnkling-carts;  the  opera- 
tion is  repeated  four  or  more  times  a  day.  The  result  is  considered 


MAINTENANCE.— REPAIRING;  CLEANSING;  WATERING.      043 

satisfactory,  and  a  considerable  saving  in  the  cost  of  keeping  the 
catch-basins  clean  is  effected,  as  well  as  the  saving  in  the  cost  of 
the  water. 

911.  Street  Sprinkling.— Streets  are  sprinkled  with  water  for  the 
purpose  of  laying  the  dust  and  cooling  the  air. 

Two  methods  of  applying  the  water  are  practised :  (1)  by  hose 
attached  to  the  fire-hydrants,  and  (1)  by  specially  constructed  carts. 

The  carts  are  preferable  to  the  hose  method;  with  the  latter 
there  is  less  regular  distribution  of  the  water,  and  in  some  localities 
there  may  be  pressure  enough  to  cause  injury  to  the  pavements. 
Again,  the  hydrants  are  generally  located  so  far  apart  that  long" 
lengths  of  hose  are  required,  and  the  constant  rubbing  soon  wears 
them  out.  To  obviate  this  metal  pipe  is  employed  in  Paris;  the 
pipes  are  usually  in  lengths  of  6£  feet,  mounted  on  two-wheeled 
trucks,  and  connected  by  flexible  joints. 

Carts  cause  less  interruption  to  traffic,  require  less  time  and 
fewer  men;  moreover,  when  there  is  a  scarcity  of  water  they  may- 
be rilled  from  wells  or  rivers. 

912.  Systems. — Three  systems  are  practised  for  carrying  out  the 
work  of  sprinkling:  (1)  by  the  municipality,  with  its  own  equip- 
ment and  men  ;   (2)  by  contract,  the  contractor  furnishing  the  labor 
and  equipment  ;  (-3)   by  contract  for  the  labor,  the  city  furnishing 
the  carts.     The  first  system  is  generally  the  most  satisfactory. 

91?.  Quantity  of  water  required. — The  quantity  of  water  re- 
quired will  vary  greatly,  depending  upon  the  character  of  the 
pavement  and  the  temperature.  The  average  number  of  gallons 
used  in  the  United  States  per  100  square  yards  is  250  ;  in  Paris 
about  120  gallons  per  square  yard  ;  in  London  about  150  gallons. 

914.  Frequency  of  Sprinkling:— The  frequency  of  sprinkling- 
will  depend  upon  local  circumstances.  In  Berlin  all  the  streets 
are  sprinkled  twice  a  day  from  April  1st  to  October  1st,  and  the- 
principal  thoroughfares  and  squares  are  sprinkled  three  and  four 
times  per  day  in  this  period.  For  this  work  the  contractor  receives 
on  an  average  $1.68  per  day  for  each  wagon.  About  150  sprinkling- 
carts  are  used,  each  holding  about  950  gallons.  The  street-car 
companies  share  the  expense  of  sprinkling  the  streets  occupied  by 
their  tracks. 

In  American  cities  the  frequency  of  sprinkling  the  streets  varies 


644  HIGHWAY    CONSTRUCTION. 

with  the  locality  and  the  seasons  of  the  year.     The  general  practice 
appears  to  be  about  as  follows : 

Paved  streets  are  sprinkled  twice  a  day  during  the  months  of 
March,  April,  and  November,  three  times  a  day  during  May  and 
October,  and  four  times  a  day  during  June,  July,  August,  and  Sep- 
tember. 

Unpaved,  macadamized,  and  gravelled,  streets  are  sprinkled 
twice  a  day  during  the  months  of  March,  April,  May,  October,  and 
November,  and  three  times  a  day  during  June,  July,  August, 
and  September. 

It  is  not  usual  to  sprinkle  the  streets  on  Sunday,  but  in  some 
few  localities  boulevards  and  driveways  used  on  that  day  are 
sprinkled  once  or  twice. 

Street  sprinkling  in  San  Francisco,  Cal.,  presents  some  unusual 
problems,  due  largely  to  the  clouds  of  dust  brought  from  the 
Western  Addition  hills  and  the  smooth  bituminous  rock  pave- 
ments on  some  of  the  streets.  The  difficulties  to  be  overcome,  as 
related  to  a  single  street,  are  stated  by  Superintendent  King  as 
follows : 

"  One  of  the  main  problems  to  be  solved  was  the  best  method 
of  sprinkling  Market  Street  from  Second  to  Van  Ness  Avenue. 
The  difficulties  to  contend  with  here  are:  (1)  a  smooth  pavement 
which  was  easily-  rendered  slippery;  (2)  the  strong  westerly  and 
northerly  winds  blowing  down  the  cross  streets  from  the  Western 
Addition  strike  the  buildings  on  the  south  side  and  blow  all  the  dirt 
from  the  south  side  of  the  street  over  to  the  north  side;  and  (3)  the 
winds  prevailing  in  the  afternoon  are  so  strong  that  when  the  street 
is  sprinkled  with  a  fine  enough  spray  to  lay  the  dust  and  still  not 
make  the  pavement  slippery,  the  water  is  so  rapidly  evaporated 
that  the  pavement  is  dry  and  dusty  before  the  cart  can  complete 
its  trip  and  return.  After  several  days7  experimenting,  it  was 
found  that  the  proper  way  to  sprinkle  this  street  is  to  sprinkle 
heavily  between  the  car-tracks,  to  sprinkle  the  north  side  of  the 
street  with  a  heavy  spray  next  to  the  gutter  and  a  light  spray  out- 
side, arid  to  leave  a  strip  about  10  feet  wide  next  to  the  outer  rail 
of  the  car-tracks  unsprinkled.  The  south  side  of  the  street  is  not 
sprinkled  at  all.  Dust  blowing  across  or  down  the  street  is  caught 
and  held  by  the  wet  pavement  and  gutter  on  the  north  side,  and 


MAINTENANCE. — REPAIRING;    CLEANSING;    WATERING.        645 

heavily  loaded  teams  have  a  dry  strip  outside  of  the  car-tracks 
upon  which  they  can  travel  without  slipping." 

915.  Cost  of  Sprinkling.— The  cost  of  sprinkling  is  variable,  de- 
pending upon  the- time  occupied  in  travelling  to  and  from  the  points 
where  the  water  is  obtained  and  where  it  is  used.     The  range  ap- 
pears to  be  from  4  mills  to  7  cents  per  1000  square  yards  sprinkled. 

In  Indianapolis  ths  average  cost  for  sprinkling  per  lineal  foot  of 
street  is  16.26  cents,  and  the  average  number  of  gallons  of  water 
used  per  square  foot  is  6.81. 

In  St.  Paul,  Minn.,  during  1894,  the  price  for  street-sprinkling 
varied  from  $12.00  to  $14.20  per  mile  per  week.  The  sprinkling 
began  April  26  and  ended  October  31.  The  cost  per  foot  front  to 
the  property  owners  is  from  4.75  to  5.3  cents  for  the  entire  season. 
These  prices  include  the  payment  of  $5.28  per  mile  per  week  to  the 
water  department  for  the  water  used.  The  average  amount  of 
water  used  was  for  July  and  August  15,100  gallons  per  mile  per 
day.  The  average  for  the  four  months  was  11,580  gallons  per 
mile  per  day. 

916.  Sea- water  and  deliquescent  salts  (as  the  chloride  of  calcium) 
have  been  used  for  street-sprinkling.    The  surface  is  kept  moist,  but 
at  the  expense  of  the  moisture  in  the  air,  and  it  is  said  that  horses' 
hoofs  are  injured  by  the  chemicals. 

In  some  cities  during  very  hot  weather  disinfectants  are  mixed 
with  the  water  used  for  sprinkling.  The  disinfectant  usually  em- 
ployed is  a  mixture  of  manganate  of  soda  one  pound,  sulphuric 
acid  half  a  pint,  ami  water  one  gallon  to  every  one  hundred  gal- 
lons of  water  used  for  sprinkling. 

Experiments  with  salt  water  have  been  made  in  San  Francisco. 
Mr.  L.  M.  King,  who  superintended  the  experiment,  says: 

"  Salt  water  binds  the  dirt  together  between  the  paving-stones, 
so  that  when  dry  there  is  no  loose  dirt  to  be  raised  by  the  wind. 
The  salt  which  is  deposited  on  the  street  absorbs  moisture  from  the 
air  during  the  night,  so  that  during  the  early  morning  the  street 
is  thoroughly  moist  and  has  the  appearance  of  having  been  freshly 
sprinkled.  This  effectually  prevents  dust  being  raised  by  the 
wind  or  street-sweepers  before  the  regular  sprinkling-carts  can  get 
over  the  ground  during  the  morning.  It  is  more  healthful  than 
fresh  water,  for  the  reason  that  salt  water  will  destroy  many  dis- 
ease-germs now  contained  in  the  dirt  on  our  streets." 


646  HIGHWAY    COXSTKUCTIOK". 

It  is  claimed  by  those  cities  which  use  salt  water  that  one  load 
is  equal  to  three  of  fresh  water. 

9 16a.  Sanding  Pavements. — In  all  European  cities  sand  is  used 
very  freely  to  prevent  the  slipping  of  horses  on  the  pavements, 
especially  on  asphalt  and  wood.  The  spreading  the  sand  and  re- 
moval of  the  ground-up  sand  add  materially  to  the  work  of  the 
cleaning  department. 

Quantity  and  Manner  of  Applying  Sand. — In  Birmingham  the 
sand  is  spread  from  a  cart  with  a  shovel,  and  the  men  who  do  this 
work  are  so  expert  that  they  can  make  an  effective  covering  of  the 
whole  street  (30  to  45  feet  wide)  with  the  use  of  only  one  load  to 
the  mile. 

On  Fifth  Avenue,  New  York,  the  contractor  was  restricted  to 
the  use  of  four  loads  to  the  block  or  eighty  loads  to  the  mile. 


CHAPTER  XX. 
TREES. 

917.  OPINIONS  differ  as  to  the  desirability  of  trees  on  roads 
•and  streets.  Some  claim  that  they  do  more  harm  than  good; 
that  they  impede  the  circulation  of  the  air,  and  that,  as  far  the 
shade  they  afford,  people  who  do  not  like  sunshine  have  only  to 
keep  on  the  shady  side  of  the  way;  that  they  deprive  the  road-sur- 
face of  the  drying  action  of  the  sun  and  air,  and  that  in  wet  weather 
the  constant  dropping  of  water  from  their  branches  keeps  the  road 
in  a  muddy  state.  Others  claim  that  trees,  especially  in  streets, 
temper  the  heat  and  serve  as  a  protection  against  dust,  that  the 
evaporation  from  their  leaves  tends  to  keep  the  surrounding  air  cool 
and  moist;  that  the  perpetual  vibration  of  their  foliage  and  sway- 
ing of  their  branches,  whilst  admitting  a  sufficient  amount  of  light, 
serve  to  protect  the  eyes  from  the  noonday  glare;  that  they  act  as 
disinfectants  by  drawing  up  and  absorbing  the  organic  matters  con- 
tained in  the  filth  from  which  the  streets  of  a  town  are  never 
free  and  which,  infiltrating  the  ground,  are  a  frequent  cause  of  fevers 
and  infection ;  and  it  is  asserted  that  on  soil  roads  some  varieties  of 
trees  both  drain  the  road  and  help  to  hold  its  earthen  surface  to- 
gether by  their  root-fibres. 

"  Those  who  have  observed  woodland  roads  closely  know  they 
are  dry  except  when  below  the  general  grade  of  the  land  or  actually 
swamped  with  water.  At  any  point  of  temperature  a  tree,  even  in 
winter  and  without  any  leaves  upon  it,  is  evaporating  moisture  from 
its  twigs,  branches,  and  trunk.  It  must  freeze  very  deep  to  prevent 
all  rcot-action,  and  whatever  moisture  roadside  trees  may  draw  from 
the  roadbed  will,  by' so  much,  prevent  the  tendency  to  muddiness 
in  any  loam  road  well  filled  with  tree-roots." 

"  Beside  the  draining  and  drying  effect  of  tree-roots,  the  fibres 

647 


648  HIGHWAY    CONSTRUCTION. 

given  to  the  soil  by  some  kinds  of  trees  (well  known  to  ploughmen  in 
all  countries)  have  a  most  salutary  effect  in  holding  the  earth  to- 
gether. If  the  soil  be  rich,  the  whole  substance  of  the  raised  and 
rounded  roadbed  may  be  completely  filled  with  horizontal  stitches, 
as  the  housewife  darns  and  runs  the  heels  of  stockings,  thus  treb- 
ling their  ability  to  resist  friction.  Eoots  in  the  surface-soil  are 
better  than  brush  to  hold  up  travel  when  they  are  alive  and  pump- 
ing water  out  of  the  ground.  If  we  are  looking  for  economy,  noth- 
ing can  be  cheaper  than  the  way  a  maple,  elm,  cottonwood,  or  white 
pine  will  fill  the  surface  of  an  earth  road  with  fibre.  The  chestnut, 
hickory,  ash,  black  walnut,  and  beach  may  all  be  thought  of  in  this 
connection,  but  only  the  close  student  of  nature  and  the  variety  of 
trees  adapted  to  different  soils  and  situations  will  succeed  in  this 
branch  of  road-making.  Yet  the  nation  has  many  thousand  miles 
of  muddy  highway  where  no  other  improvement  seems  possible." 

"  There  is  a  use  for  the  overhanging  branches  of  trees  in  winter 
They  shade  the  road  and  permit  it  to  freeze  or  remain  solid  when, 
but  for  the  shadow,  the  road  would  be  softening  in  the  sun.  The 
branches  work  in  this  way  to  prevent  and  protect  the  road  from 
being  cut  in  pieces.  The  traveller  and  his  weary  team,  swamped  in 
thawed  earthen  roads,  are  glad  to  reach  the  frozen  track  on  the 
north  side  of  a  bit  of  woodland.  And  the  man  who  would  cut  away 
roadside  shades  so  as  to  let  all  our  earth  roads  thaw  out  and  settle 
together  is  very  much  mistaken." 

Trees  also  serve  to  make  the  border  of  the  road  discernible  at 
night  as  well  as  after  snowdrifts,  thereby  warning  the  travellers 
against  embankments  and  other  dangers  along  the  sides  of  the  road. 

918.  In  France,  as  far  back  as  the  middle  of  the  sixteenth  cen- 
tury, trees  were  planted  along  the  royal  roads.     This  practice  ha& 
been  more  or  less  continuously  followed. 

During  several  periods  it  was  stopped  by  those  in  authority, 
.they  being  of  the  opinion  that  trees  were  more  of  a  damage  than  a 
benefit.  But  now  trees  are  planted  along  all  roads  having  a  width 
greater  than  10  metres  (32.8  feet).  They  are  placed  at  distances 
varying  from  5  to  10  metres  (16.4  to  32.8  feet),  in  single  rows  upon 
the  narrow  roads,  and  in  double  rows  upon  the  wider. 

919.  "The  roads  of  Belgium  are  flanked  on  either  side  by  two 
and  sometimes  four  rows  of  shade-trees,  which  add  much  to  the 
beauty  of  the  country  through  which  they  run." 


TREES.  649 


920.  Financial  Value  of  Trees. — Take  two  streets  in  all  respects 
alike,  except  that  one  has  trees  well  selected,  set  at  suitable  dis- 
tances apart  and  well  cared  for,  the  other  with  no  trees  or  with 
trees  carelessly  set  and  neglected,  as  frequently  happens.     A  person 
wishing  to  purchase  a  residence  will  undoubtedly  select  the  street 
having  the  fine  trees,  although  he  may  have  to  pay  more  than  many 
times  the  cost  of  the  trees.     Thus  from  a  financial  standpoint  trees 
pay. 

921.  In  Saxony  a  considerable  revenue  is  derived  from  fruit- 
trees  planted  on  the   roadsides.     The  trees  are  cared  for  by  the 
roadmen  in  so  far  as  professional  knowledge  is  not  required;  they 
remove    insects,   clear    the    tree-frames    of    rubbish,   and    water 
them. 

In  sections  where  fruit-trees  cannot  be  cultivated  on  account  of 
climatic  causes,  or  where  they  would  be  liable  to  wanton  damage 
and  plundering  of  the  fruit,  forest-trees  are  planted. 

The  state-road  fruit-trees  are  leased  to  the  highest  bidders,  and 
the  money  received  is  covered  into  the  state  treasury.  The  lessees 
of  the  fruit-trees  are  held  to  a  strict  account  for  any  damage  done 
the  trees.  Ladders  must  be  used  to  gather  the  fruit,  and  any 
battering  of  the  trees  with  clubs  or  poles  to  get  the  fruit  down  is 
prohibited  and  is  punishable  by  fine. 

922.  Selection  of  Trees.— Trees  should  be  selected  with  refer- 
ence to  the  climate,  locality,  quality  of  soil,  extent  of  space,  and 
circumstances  of  surroundings  in  general. 

Large-growing  varieties  should  be  selected  for  places  of  great 
extent,  smaller  varieties  for  places  of  less  extent.  A  low  compact 
tree  is  not  suitable  for  street  planting. 

The  qualities  necessary  in  a  good  street  tree  are  that  it  must  be 
hardy,  must  not  be  affected  by  a  long-continued  drought,  heat  must 
not  wither  it  nor  make  it  look  rusty;  it  must  be  able  to  withstand 
dust,  smoke,  soot,  foul  air,  and  the  insidious  attacks  of  insects,  and 
be  able  to  recover  from  any  malicious  or  accidental  injury  it  may 
receive. 

The  tree  must  be  of  rapid  growth  and  develop  a  straight,  clean 
stem  with  shady  foliage.  It  must  be  graceful  either  in  full  leaf 
or  when  bare,  as  in  winter;  its  roots  must  not  require  too  much 
room,  and  they  must  be  able  to  withstand  the  effects  of  pollution 
or  rough  treatment. 


650  HIGHWAY   CONSTRUCTION. 

As  to  wnat  variety  to  select  very  little  can  be  said;  a  large 
quantity  of  suitable  trees  exists  from  which  one  may  select  as  local 
conditions  or  fancy  may  dictate. 

923.  Precautions   to    be    taken    in    the    Selection. — Whatever 
variety  of  tree  is  selected,  the  following  precautions  should  be  taken 
to  insure  its  nourishing: 

(1)  The  young  tree  should  have  been  well  nourished  in   the 
nursery;  it  should  not  be  planted  on  the  street  until  its  stem  is 
over  8  feet  in  height  and  about  3  inches  in  diameter.     The  stem 
should  be  clean  and  straight,  and  the  whole  tree  symmetrical. 

(2)  The  ground  where  a  tree  is  to  be  set  should  be  examined  to 
see  whether  it  is  suitable  for  tree-growth.     If  it  is  not,  the  poor 
material  should  be  removed  and  good  soil  substituted.     The  amount 
to  be  removed  depends  upon  circumstances  and  can  be  determined 
by  examination.     A  tree  to  flourish  must   have   plenty  of  good 
ground  in  which  to  grow;  it  should  be  good  to  the  depth  of  at 
least  3  feet,  and  an  equal  distance  in  all  directions  from  the  trunk 
when  practicable.  The  amount  of  good  soil  is  of  greater  importance 
than  the  shape  it  is  in.     The  further  the  tree  is  planted  from  the 
curb  the  better,  so  as  not  only  to  give  it  a  larger  body  of  soil,  but 
to  lessen  the  risk  of  killing  the  tree  by  the  pollution  of  the  ground 
with  gas  from  defective  pipes  and  also  excess  of  moisture  from  the 
gutters. 

924.  Distance  Apart  to  plant  Trees  generally  appears  to  be  a 
matter   of   choice,  but   this  should   not   be  so.     Trees  should   be 
placed  so  far  from  one  another  that  at  maturity  they  will  not  meet. 
Such  distances  will  enable  them  to  develop  in  their  natural  beauty. 
To  determine  the  proper  distance  apart  measure  the  spread  of  full- 
grown  trees  of  the  same  variety  as  those  to  be  planted ;  it  will  vary 
from  30  to  50  feet.     The  trees  should  alternate  on  opposite  sides  of 
the  street. 

925.  Trees  at  Street-intersections. — Where  streets  cross  at  right 
angles  or  nearly  so,  two  trees  of  large-growing  varieties  may  be 
placed  on  each  corner,  far  enough  from  the  corner  of  the  curb 
not  to  interfere  with  the  catch-basin  when  there  is  one.     Each 
tree  should  be  placed  on  the  tree  line  of  one  street  and  the  fence 
line  of  the  other;  this  will  require  eight  trees  to  every  intersection. 
The  trees  so  planted  should  form  a  handsome  mass  of  foliage  and 
afford  an  agreeable  shade  where  most  needed.     At  some  intersec- 


TREES. 


051 


tions  it  may  not  be  possible  to  plant  all  the  eight  trees,  but  as 
many  as  can  should  be  placed. 

926.  Protection  of  Trees. — Each  tree  should  be  protected  with 
a  light  iron  railing  to  prevent  mischievous  persons  from  cutting 
their  names  on  or  otherwise  injuring  the  trunk. 

Where  it  is  necessary  that  the  footpath  be  entirely  paved  the 
space  around  each  tree  may  be  arranged  as  shown  in  Fig.  177.  A 
light  stone  curb  is  placed  around  the  tree  in  a  circle  the  diameter 
of  which  should  be  about  4  feet,  and  the  curb  should  project  above 
the  pavement  about  3  to  G  inches;  this  prevents  people  from  walk- 
ing on  the  earth,  keeps  the  ground  from  becoming  hard,  and 
permits  air  and  water  to  enter  to  the  roots.  Or  a  cast-iron  grating 
4  feet  square  may  be  employed  for  the  same  purpose. 


FIG.  177.    PROTECTION   OF  TREES  IN  WALKS. 

927.  Specifications  for  Protection  of  Trees. — The  contractor 
TV  hen  directed  shall  protect  from  injury  trees  upon  the  line  of  the 
work,  and  the  grading  around  them  must  be  carefully  done.  The 
grass  sodding  on  the  sidewalks  must  also  be  protected  as  much  as 
possible. 


CHAPTER  XXL 
STAKING  OUT  THE  WORK. 

928.  THE  staking  out  of  the  work  consists  in  placing  stakes  in 
the  ground  to  direct  the  workmen  and  define  the  limits  of  the- 
work. 

The  centre  line  of  the  proposed  road  is  marked  by  stakes  set 
(usually)  at  distances  apart  of  100  feet  on  the  straight  portions, 
and  at  15,  25,  or  30  or  50  feet  on  curves,  depending  upon  their 
sharpness;  on  the  stakes  the  cut  or  fill  at  that  point  is  marked. 

929.  The  staking  out  of  straight  lines  and  simple  curves  of 
less  than   100  feet   radius  presents  no  great  difficulty;  curves  of 
greater  radius,  compound  or  reverse,  will  require  to  be  set  out  by 
the  same  formula  and  methods  as  are  empleyed  for  setting  out  the 
curves  on  railroads.     For  detailed  instructions,  etc.,  any  one  of  the 
many  railroad-engineer's  pocket-books  may  be  used,  such  as  Henck's, 
Trautwine's,  or  Shunk's. 

930.  Side  Slopes. — The  setting  of  the  slope  stakes  on  ground 
that  is  level  or  nearly  so  at  right  angles  to  the  centre  line  is  a  sim- 
ple matter,  the  position  of  the  stake  being  found  by  adding  together 
the  half-width  of  the  roadway,  and  the  base  of  the  triangle  ob- 
tained by  multiplying  the  depth  by  the  ratio  of  the  slope.     When 
the  natural  surface  of  the  ground  is  inclined,  the  setting  of  tho 
slope  stakes  is  less  simple.     The  ordinary  method  employed  is  a 
tentative  process  of  combined  levelling  and   calculation,  which  is 
nothing  better  than  a  rule  of  thumb.     The  manner  of  procedure 
is  as  follows:  Suppose  it  is  desired  to  set  the  stakes  D  and  E,  Fig. 
178.     The  depth  of  the  cutting  at  C  is  ascertained,  and  a  point  h 
taken  on  the  surface  where  it  .is  assumed  the  slope  will  cut;  its 
height  above  AB  is  obtained;  this  height  is  multiplied  by  the  ratio 
of  the  slope,  and  the  half  -width  A  C  or  CB  added :  if    ihis  agrees 
with  the  distance  of  the  assumed  point,  that  point  may  be  taken  as 

652 


STAKING   OUT   THE   WORK. 


653 


correct;  if  not,  a  second  trial  must  be  made.    A  difference  of  6 
inches  will  be  of  no  practical  importance. 


A  C  B 

FIG.  178.    MANNER  OF  SETTING  SLOPE  STAKES. 

The  guessing  may  be  aided  by  taking  levels  at  the  points  F  and 
{JT,  and  performing  the  calculations  as  outlined  above. 

A  more  accurate  and  sometimes  a  more  expeditious  method  is 
as  follows : 

Take  a  cross-section  book,  and  on  each  page  plot  the  cross-sec- 
tion of  the  ground  at  each  station,  and  draw  the  slope  lines;  the 
•exact  distances  can  then  be  obtained  at  a  glance  by  counting  the 
spaces  between  the  centre  line  and  the  point  where  the  side  slope 
intersects  the  natural  surface. 

Slope  stakes  are  required  at  every  centre  stake  along  the  line, 
and  also  where  the  ground  is  very  rough  at  intermediate  distances. 

931.  Setting  out  Culverts. — The  length  of  a  culvert  which 
passes  under  an  embankment  is  less  than  the  distance  between  the 
bottom  of  the  opposite  side  slopes,  and  may  thus  be  found :  From 
the  height  of  the  embankment  H,  Fig.  179,  take  the  above  ground 
height  of  the  culvert  li\  the  remainder  will  be  the  height,  &„  of  the 
embankment :  then  the  required  length  ab  is  equal  to  the  top  width 
of  the  embankment  cd,  plus  the  width  of  the  base  of  the  slopes  on 
the  top  of  the  culvert.  Thus  if  CD  equal  30  feet,  and  hl  equal  5 
feet,  the  ratio  of  the  slopes  1£  to  1,  the  length  ab  will  be 

30  +  (5  X  3)  =  30  +  15  =  45  feet. 


HIGH WA Y    C01>  ST  RUCTION. 


932.  When  the  natural  surface  of  the  ground  is  horizontal,  the 
length  of  any  structure  passing  under  an  embankment  will  lie 


FIG.  179. 

half  on  each  side  of  the  centre  line.     When  the  natural  surface  is 
inclined,  the  ends  of  the  structure  will  be  at  different  distances 


Fig,  180; 


Fig,18L 


from  the  centre  line,  according  to  the  slopes  of  the  ground.  This 
is  seen  in  Figs.  180  and  181,  the  first  of  which  represents  the 
section,  and  the  second  the  plan,  of  an  embankment.  The  lines  $$ 


STAKING   OUT   THE   WORK.  055 


and  00,  representing  the  ends  of  a  culvert  passing  beneath  the 
embankment,  are  seen  to  be  at  different  distances  from  the  centre 
line.  The  position  of  the  points  S  and  0  may  be  found  by  first 
getting  from  the  tables  of  side  width  the  points  A  and  D,  and 
measuring  in  from  these  points  the  distances  AS  and  DO,  de- 
pending upon  the  slopes  AB  and  AD.  In  the  case  of  the  upper 
end  the  distance  of  SS  from  A  will  be  less  than  if  the  natural  sur- 
face was  level;  at  the  lower  end  the  distance  from  D  to  0  will  be 
greater.  Having  found  the  distances  of  SS  and  00  from  the 
centre  line,  we  get  the  position  and  length  of  the  wing  walls  of  the 
culvert  by  drawing  a  line  from  >SY  to  any  desired  angle  to  intersect 
the  slope  A  A ;  and  upon  the  lower  side  of  the  embankment  we  get, 
in  the  same  manner,  the  lines  DD,  OD,  the  latter  being  of  course 
longer  than  the  wings  upon  the  upper  side  AS,  AS. 

933.  Setting  out  Bridge  Work.— In  laying  out  the  abutments 
for  bridges  there  are  numerous  cases  to  be  considered, — as  whether 
the  bridge  is  on  the  square  or  on  the  skew,  upon  a  level  or  a 
gradient,  upon  a  curve  or  a  straight  line,  and  whether  the  natural 
surface  is  horizontal  or  inclined;  the  position  and  form  of  abut- 
ments and  wing  walls  depending  so  much  upon  the  various  condi- 
tions  affecting  each  particular  case,  that  any  attempt  to  lay  down 
general  rules  for  each  work  would  be  of  little  use. 

934.  Staking  out  Drains. — The  method  of  setting  grade  marks 
for  drains  is  as  follows : 

At  every  50  feet  along  the  line  of  the  trench  place  a  board  a 
couple  of  feet  wider  than  the  width  of  the  trench,  bed  it  firmly  in 
the  earth  and  mark  the  centre  line  on  it ;  then  ascertain  the  level 
of  the  boards,  calculate  depth  of  cutting  at  each  one,  and  mark  it 
plainly  on  each  board.  To  transfer  the  grade  line  to  the  bottom 
of  the  trench,  procure  a  measuring-rod  (say  0  feet  long),  subtract 
the  depth  of  cutting  from  the  length  of  the  rod,  and  to  the  board 
that  straddles  the  ditch  nail  a  piece  of  board  upright,  the  height 
of  which  above  the  horizontal  board  is  equal  to  the  difference 
found.  This  operation  being  performed  at  each  board,  a  line 
stretched  from  the  upright  pieces  will  be  parallel  to  the  grade  lino 
and  six  feet  above  the  bottom  of  the  trench. 

935.  Vertical  Curves. — As  stated  in  Article  610,  the  apex  or 
meeting  point  of   grades   require   to  be  rounded  off   by  vertical 
curves,  thus  slightly  changing  the  grade  at  and  near  the  point  of 


656  HIGHWAY   CONSTRUCTION". 


intersection.     A  vertical  curve  rarely  need  extend  more  than  200 
feet  each  way  from  that  point  (Fig.  182). 

Let  AB,  BC,  be  two  grades  in  profile,  intersecting  at  station  B, 
and  let  A  and  0  be  the  adjacent  stations.  It  is  required  to  join 
the  grades  by  a  vertical  curve  extending  from  A  to  C.  Suppose  a 


i**"  7    i 

; 

i      i      « 

i_         j:          -'  . 

!     i     i 

Li  J 

• 
i 
i 
I 
j. 

FIG.  182. 

chord  drawn  from  A  to  C.  The  elevation  of  the  middle  point  of 
the  chord  will  be  a  mean  of  the  elevations  of  grade  at  A  and  (7, 
and  one  half  of  the  difference  between  this  and  the  elevation  of 
grade  at  B  will  be  the  middle  ordinate  of  the  curve.  Hence  we 
have 

M  =  j  (grade  A  +  grade  C  _ 

in  which  M  equals  the  correction  in  grade  for  the  point  B.  The 
correction  for  any  other  point  is  proportional  to  the  square  of  its 
distance  from  A  or  C.  Thus  the  correction  at  A  -}-  25  is  y1-^  M', 
at  A  +  50  it  is  £  M\  at  A  -j-  75  it  is  -fa  M]  and  the  same  for  cor- 
responding points  on  the  other  side  of  B.  The  corrections  in  the 
case  shown  are  subtractive,  since  M  is  negative.  They  are  additive 
when  M  is  positive,  and  the  curve  concave  upward. 

936.  Staking  out  Contour  of  Street  Foundations. — In  order  to 
insure  the  proper  transverse  form  of  street  pavements,  stakes 
should  be  driven  across  the  street,  the  tops  of  which  shall  cor- 
respond to  the  intended  contour.  The  stakes  should  be  placed 
longitudinally  of  the  street  at  distances  not  exceeding  16  feet,  and 
transversely  at  distances  not  exceeding  10  feet.  After  the  stakes 
are  placed  ridges  of  concrete  may  be  formed  along  the  street,  as 
shown  in  Fig.  183.  After  the  ridges  or  small  banks  of  concrete  are 


STAKING    OUT   THE    WORK. 


657 


so  placed  the  filling  of  the  interspaces  may  be  proceeded  with,  and 
a  straight-edge  resting  on  the  ridges  will  guide  the  workmen  in 
keeping  the  concrete  to  the  proper  form ;  or  the  stakes  may  be 
placed  as  directed  above  and  a  thin  slat  nailed  to  their  tops,  the 
concrete  filled  in  and  made  flush  with  the  top  of  the  slat,  a  straight- 
edge 17  feet  long,  its  ends  resting  on  the  slats,  being  used  for  this 


FIG.     183.    MANNER    OF     FORMING    CONTOUR    OF 
STREETS. 

purpose.     After  the  concrete  is  thoroughly  set  the  slats  may  be 
removed  and  the  space  they  occupied  plastered  over  with  cement. 

937.  Setting  Stakes  for  Curb.— Stakes  for  setting  curb  should  be 
placed  on  the  front  line  of  the  curb,  with  their  tops  at  the  required 
grade.  Their  distance  apart  should  not  exceed  50  feet,  and  on  cir- 
cular work  will  require  to  be  closer.  At  street  corners  three  stakes 
should  be  driven,  one  at  the  intersection  point  of  the  meeting  curbs, 
and  one  at  each  tangent  point  (Fig.  184). 


•Stake 


FlQ.  184.    SHOWING  MANNER  OF  SETTING  STAKES  FOR 

CURBS- 

938.  In  placing  the  stakes  for  any  structure  they  should,  be 
placed  so  far  outside  of  the  work  that  they  will  remain  undisturbed 
during  the  construction  of  the  work.  They  must  be  so  placed  that 
lines  stretched  from  any  two  of  them  wiP  define  the  corner  and 


658 


HIGHWAY   CONSTRUCTION", 


face  of  the  structure  (Fig.  185).     Stakes  for  defining  the  boundaries 
of  an  excavation  may  be  placed  at  the  angles  thereof. 


*.-— 


T 


Stake*  - 


iStake  ; 

FIG.  185.    MANNER  OF  SETTING  STAKES   FOR  STRUC- 
TURES. 

939.  Two  stakes,  at  a  sufficient  distance  apart  upon  the  land, 
will  fix  any  line  upon  the  water;   and  two  sets  of  stakes,  upon 
different  lines  upon  the  shore,  will  by  their  intersection  fix  any 
point  upon  the  water  with  accuracy  sufficient  for  many  purposes. 
For  exact  work,  however,  a  transit  should  be  employed  to  fix  a  line; 
and  two  angular  instruments,  in  well-chosen  positions,  will  deter- 
mine any  point. 

940.  Bench  Marks. — A  permanent  bench  or  reference  mark  for 
levels  should  be  established  with  care,  in  the  immediate  neighbor- 
hood of  any  proposed  structure,  from  which  the  elevations  of  the 
various  parts  may  be  obtained.     Such  bench  marks  should  also  be 
fixed  at  the  commencement   of  long  cuttings,  and  generally  at 
intervals  of  from  500  to  1000  feet  along  the  works,  a  list  of  such 
elevations  being  entered  in  the  engineer's  note-book. 


CHAPTER  XXII. 
SPECIFICATIONS  AND  CONTRACTS. 

941.  Specifications.— A  specification  or  detailed  description  of 
the  various  works  to  be  carried  out  is  always  attached  to  a  contract, 
and  is  prepared  before  estimates  are  called  for.  The  prominent 
points  in  connection  with  specifications  are  as  follows: 

(1)  Description  of  the  work. 

(2)  Extent  of  the  work. 

(3)  Quality  of  the  materials. 

(4)  Testing  of  the  materials. 

(5)  Delivery  of  materials. 

(6)  Character  of  the  workmanship. 

(7)  Manner  of  executing  the  work. 

(8)  Time  of  commencement. 

(9)  Time  of  completion. 

(10)  Manner  and  times  of  payment. 

(11)  Penalties  for  infraction. 

(12)  Such  general  instructions  and  stipulations  as  may  be  found 
necessary  in  each  case. 

Attention  to  these  points  and  a  clear  and  accurate  description 
of  each  detail  (leaving  nothing  to  be  imagined)  will  not  only 
materially  contribute  to  the  rapid  and  efficient  execution  of  the 
work,  but  will  avoid  all  future  misunderstandings. 

942.  Concerning  Tests  of  Materials. — While  proper  tests  should 
always  be  stipulated,  yet  if  they  are  carried  to  an  extreme  degree, 
as  frequently  happens,  they  defeat  their  own  object.  When  it  be- 
comes impossible  to  carry  out  certain  unreasonable  demands,  the 
alternative  is  to  evade  them  as  much  as  possible;  and  it  must  al- 
ways be  borne  in  mind  that  the  more  stringent  the  demand,  the 
greater  the  difficulty  in  enforcing  it. 

659 


660  HIGHWAY    CONSTRUCTION. 

943.  Contracts. — A  good,  clear,  and  comprehensive  contract  is 
a  difficult  thing  to  write,  but  it  should  be  "  common-sense  "  from 
beginning  to  end,  and  should  be  the  joint  production  of  both  en- 
gineering and  legal  ability,  neither  sacrificing  the  one  feature  to 
the  other. 

GENERAL   SPECIFICATIONS. 

The  following  specifications,  in  conjunction  with  those  given 
throughout  the  work,  will  aid  in  preparing  specifications  for  the 
different  works  connected  with  highways. 

944.  Clearing. — The  land  will  be  cleared  to  the  width  of 

feet  on  each  side  of  the  centre  line,  and  on  each  section  must  be 
entirely  completed  before  grading  is  commenced. 

The  clearing  must  be  done  in  such  manner  that  all  useful 
timber  may  be  saved.  Trees  of  large  dimensions  shall  be  trimmed 
and  put  into  the  most  profitable  shape  for  the  market;  when  so 
trimmed  they  shall  be  piled  in  such  places  along  the  line  of  the 
road  as  the  engineer  may  designate. 

Brushwood,  stumps,  tree  limbs,  etc.,  must  not  be  cast  upon  the 
adjacent  land,  but  shall  be  formed  into  piles  and  burned;  stumps 
and  other  material  that  will  not  burn,  must  be  removed  from  the 
work  and  disposed  of  by  the  contractor.  All  brush  or  trees  acci- 
dentally or  otherwise  thrown  upon  the  adjacent  lands  must  be 
taken  off  and  disposed  of  as  above  described.  The  land  when 
cleared  must  be  left  in  a  clean  condition,  and  the  contractor  will 
be  held  responsible  for  all  damage  to  crops,  fences,  fruit-trees,  and 
timber  of  adjacent  owners. 

945.  Close  Cutting. — Where  embankments  are  to  be  formed  more 
th#n  one  foot  in  height,  the  stumps  shall  be  chopped  close  to  the 
ground. 

946.  Grubbing. — Where   excavations   do   not  exceed  2  feet  in 
depth,  or  embankments  one  foot  in  height,  all  stumps  shall  be 
grubbed  out.     The  catch-water  drains,  side  ditches,  and  off-take 
drains  shall  be  grubbed  wherever  required. 

947.  Grading. — Grading  will  include  all  excavations  and  em- 
bankments required  to  form  the  roadway,  all  excavations  and  em- 
bankments required  for  altering  the  level  of  intersecting  roads. 
Excavations  for  the  foundations  of  all  structures,  excavations  for 
all  trenches  and  ditches,  excavations  required  for  the  altering  of 


SPECIFICATIONS   AND   CONTRACTS.  661 

the  channels  of  streams,  etc.,  and  all  other  excavations  and  em- 
bankments that  may-  be  required  for  the  full  completion  of  the 
road. 

The  grading  shall  be  executed  in  accordance  with  the  lines  and 
grades  given  by  the  engineer.  The  portions  which  are  above  grade 
are  to  be  excavated,  and  such  and  so  much  of  the  excavated  mate- 
rial as  may  be  suitable  for  the  purpose,  and  as  may  be  necessary, 
shall  be  filled  in  those  parts  which  are  below  the  grade  lines.  The 
material  excavated,  not  so  used  for  filling,  shall  be  placed  in  spoil- 
banks  at  such  points  as  the  engineer  designates,  or  it  may  be  re- 
moved from  the  line  of  the  work  by  the  contractor  for  his  own  use 
and  benefit,  if  so  directed. 

Where  embankments  are  to  be  formed  of  a  height  less  than  3 
feet,  all  top-soil  and  vegetable  matter  must  be  excavated  to  such 
depth  as  the  engineer  may  direct.  The  material  so  excavated 
will  be  piled  up  outside  of  the  embankment  lines,  and  afterwards 
used  to  cover  the  slopes  of  embankments  and  cuttings;  the  surplus 
that  remains  after  completing  this  work  shall  be  removed  and 
placed  in  spoil-banks  at  such  places  as  will  be  designated  by  the 
engineer,  or  it  may  be  removed  by  the  contractor  for  his  own  use 
and  benefit.  In  places  where  the  embankments  exceed  3  feet  in 
height  the  perishable  matter  shall  be  removed,  but  no  excavation 
done  unless  specially  ordered  by  the  engineer. 

All  sloping  ground  covered  with  pasture  shall  be  deeply 
ploughed  over  the  base  of  the  embankments  before  the  latter  are 
commenced.  On  slopes  which  have  been  covered  with  timber  the 
slope  shall  be  cut  into  steps  before  the  embankment  is  commenced, 

948.  Formation  of  Embankments. — Embankments  of  a  height 
less  than  3  feet  shall  be  made  by  horses  .and  carts.  Embankments 
of  greater  height  may  be  formed  by  tipping  from  dump-cars  travel- 
ling on  a  track. 

The  embankments  will  be  formed  to  such  height  above  the 
sub-grade  as  the  engineer  may  direct,  to  provide  for  shrinkage, 
compressions,  washing,  and  settlement,  and  they  must  be  main7 
tained  to  the  required  height,  width,  and  shape  until  accepted. 
Whenever  embankments  are  made  from  side  ditches,  the  width  of 
the  berm  to  be  left  at  the  foot  of  the  slopes  will  be  given  by  the 
•engineer. 

In   the  formation  of   embankments  no  mud,  muck,  vegetable 


662  HIGHWAY   CONSTRUCT] OX. 

matter,  tree  stumps,  or  other  materials  which  the  engineer  may 
deem  unsuitable,  will  be  allowed  to  be  used.  Such  material  must 
be  removed  from  the  line  of  the  work  and  disposed  of  as  the 
engineer  may  direct. 

After  completion,  the  slopes  of  all  cuttings  and  embankment? 
will  be  covered  to  a  depth  of  6  inches  with  the  loam  and  vegetable 
soil  previously  reserved  for  this  purpose,  or  such  shall  be  obtained 
from  such  places  as  the  engineer  may  direct. 

The  slopes  of  embankments  will  generally  be  1|  to  1,  of  earth 
excavations  2  to  1,  of  rock  excavations  1  to  1 ;  and  no  allowance  for 
excavations  outside  the  limits  of  these  slopes  will  be  made  unless 
specially  ordered  by  the  engineer. 

The  widths,  slopes,  and  other  dimensions  may  be  varied  at  any 
time  by  the  engineer  to  suit  circumstances. 

In  the  event  of  slips  occurring  in  excavations,  the  contractor 
will  remove  the  debris  and  reslope  the  work.  If  the  slips  occur 
through  carelessness  on  the  part  of  the  contractor,  no  allowance 
for  the  removal  or  reshaping  will  be  made;  but  if  they  occur 
through  unavoidable  causes,  he  will  be  paid  for  it  as  loose  rock  er- 
as earth,  according  to  the  class  to  which  it  may  appear  to  the 
engineer  to  belong. 

Rock  shall  be  excavated  to  a' depth  of  two  feet  below  the  sub- 
grade  level  and  the  space  refilled  with  stone  broken  to  a  size  not 
exceeding  2^  inches. 

In  the  event  of  work  being  proceeded  with  in  winter,  no  snow 
or  ice  will  be  placed  in  embankments  or  allowed  to  be  covered  up 
in  them,  and  all  frozen  earth  must  be  excluded  from  the  heart  of 
the  embankment. 

949.  Earth-work  Measurement  and  Classification. — All  earth- 
work shall  be  measured  in  excavation,  and  will  be  classified  under 
the  following  heads,  viz.,  earth,  loose  rock,  solid  rock. 

Earth  will  include  clay,  sand,  gravel,  loam,  decomposed  rock, 
and  slate,  stones  and  bowlders  containing  less  than  one  cubic  foot, 
and  all  other  matters  of  an  earthy  nature,  however  compact  they 
may  be. 

Loose  rock  will  include  all  bowlders  and  detached  masses  of 
rock  measuring  more  than  one  cubic  foot  and  less  than  one  cubic 
yard;  also  hardpan,  compact  gravel,  sandstone,  and  all  other 
materials  of  a  rock  natu;e  (except  solid  rock)  which  may  be 


SPECIFICATIONS  AND   CONTRACTS. 


loosened  with  the  pick,  although  blasting  may  be  resorted  to  in 
order  to  expedite  the  work. 

Solid  rock  will  include  all  rock  found  in  place  in  ledges,  and  in 
musses  or  bowlders  measuring  more  than  one  cubic  yard,  and  which 
can  only  be  removed  by  blasting,  which  fact  will  be  determined  by 
the  engineer. 

950.  Drains. — At  such   places   as   may  be   designated   by  the 
engineer,  drains  will  be  formed   in   the   following   manner:   the 
trenches  will  be  opened  to  the  width  and  several  depths  given  by 
the  engineer.     In  the  trenches  so  opened  drains  of  tiles  will  be 
constructed,  as  directed  by  the  engineer. 

The  tiles  furnished  shall  be  the  best  quality  of  clay  or  terra- 
cotta, manufactured  expressly  for  drainage  purposes;  they  shall 
be  in  lengths  of  not  less  than  one  foot,  and  shall  be  of  uniform 
diameter  throughout.  A  pipe  of  larger  diameter,  broken  in  half, 
will  be  used  for  collars;  the  pipes  will  be  laid  true  to  grade  and 
the  trenches  filled  in  with  round  field  stones.  The  stones  must 
not  be  thrown  in,  but  shall  be  laid  in  carefully  by  hand,  the  largest 
stones  being  used  to  wedge  the  pipes  in  place;  on  top  of  the  stone 
filling  place  good  sods,  with  the  grass  side  down.  Silt-basins  will 
be  constructed  of  brick,  of  the  forms  and  dimensions  shown  on 
plans,  at  the  points  designated  by  the  engineer. 

951.  Catch-water   Ditches. — Catch-water    ditches  will    be   ex- 
cavated at  the  top  of  the  slope  of  all  excavations  on  the  up-hill 
side  only;  they  shall  be  excavated  not  closer  than  6  feet  to  the 
edge  of  the  slope;  they  shall  be  excavated  on  the  lines  and  to  the 
grades  given  by  the  engineer. 

952.  Off-take  Ditches. — These  ditches  will  be  excavated  where- 
ever  directed  by  the  engineer,  and  will  have  such  form  and  dimen- 
sions as  he  may  direct. 

The  contractor  shall  also  excavate  and  form  all  other  drains 
and  ditches  which  the  engineer  may  deem  necessary  for  the  proper 
drainage  of  the  road. 

953.  Rip-rap. — In  cases  where  slopes  require  protection  from 
the  action  of  water,  the  protection  works  will  be  constructed  of 
brush  or  stones,  and  will  be  carefully  performed  in  such  manner 
and  of  such  dimensions  as  the  engineer  may  direct. 

954.  Retaining,  Breast,  Slope,  and  Parapet  Walls.— These  walls 


GG4  HIGHWAY    CONSTRUCTION. 

will  be  constructed  at  such  places  and  in  such  manner  as  may  be 
directed  by  the  engineer. 

955.  Culverts  formed  of  earthenware,  cast-iron  pipe,  stone  laid 
dry  or  in  mortar,  will  be  constructed  wherever  directed  by  the  en- 
gineer.     Their  form  and   dimensions  shall   correspond  with  the 
detailed  plans  prepared  therefor. 

MASONRY. 

Stone  masonry  will  be  classified  as  follows : 

956.  First-class  Masonry  shall  be  built  of  sound  stone,  of  a  quality 
to  be  approved  by  the  engineer;  it  will  consist  of  large  rectangular 
stones,  with  the  beds  dressed  parallel  throughout,  and  the  vertical 
sides  hammer-dressed  so  as  to  form  quarter-inch  joints;  the  stones 
will  be  left  quarry-faced  except  when  otherwise  ordered;  rock-faced 
stones  to  have  a  one-inch  chisel-draught  cut  on  all  four  edges  of  the 
face,  and  no  face  projection  greater  than  3  inches. 

The  rise  of  the  courses  of  first-class  masonry  will  not  be  less  than 
12  inches,  and  may  range  up  to  24  inches,  the  thinnest  courses  being 
invariably  placed  towards  the  top  of  the  work;  the  stones  in  adja- 
cent courses  shall  break  joints  by  at  least  one  foot. 

Headers  shall  be  built  in  every  course  not  further  apart  than  6 
feet;  they  will  have  a  length  in  the  face  of  the  wall  of  not  less  than 
24  inches,  and  they  must  run  back  at  least  2^  times  their  height; 
when  they  will  not  allow  this  proportion,  they  must  pass  through 
from  front  to  back.  Stretchers  shall  have  a  minimum  length  in  the 
face  of  the  wall  of  30  inches,  and  their  breadth  of  bed  shall  be  at 
least  1-J  times  their  height.  First-class  masonry  will  be  laid  in 
Portland  cement  mortar,  and  each  course  must  be  thoroughly 
grouted  before  the  next  course  is  started.  Each  stone  shall  be 
cleaned  and  dampened  before  being  set.  Improperly  dressed  stones 
must  be  recut  before  placing  in  the  wall,  as  no  hammering  will  be 
allowed  after  the  stones  are  set. 

First-class  masonry  will  include  all  dimension  stone,  such  as 
coping,  cap-stones,  bridge  seats,  and  parapets,  abutments,  and  piers 
of  large  bridges. 

957.  Second-class  Masonry  will   include  retaining-walls,  abut- 
ments, wing  walls  and  parapets  of  minor  bridges,  and  head  walls  on 
"box  culverts.     It  will  consist  of  broken  range-work,  built  of  such 
stone  as  may  be  approved  by  the  engineer;  the  stones  shall  be  dressed 


SPECIFICATIONS   AND    CONTRACTS.  G65 

to  horizontal  beds  and  vertical  joints ;  the  face  shall  be  "  rock  face/' 
with  edges  pitched  to  line,  with  no  face  projections  exceeding  2 
inches.  At  least  one  third  of  the  stones  must  be  headers  evenly 
distributed  through  the  wall;  the  mortar  joints  shall  not  exceed  one 
half -inch  in  thickness.  All  vertical  joints  must  be  broken  by  at 
least  6  inches.  No  stone  will  be  allowed  in  the  face  of  the  wall 
which  has  a  less  area  than  72  square  inches.  Quoin  stones  shall 
have  a  chisel-draught  one  inch  wide  cut  on  each  side  of  the  angle. 

The  backing  and  foundation  will  be  of  large  sound  stones, 
roughly  squared,  no  stone  to  measure  less  than  2  cubic  feet.  The 
broadest  bed  will  be  laid  underneath,  and  must  have  a  good  bearing 
o>n  the  stones  below.  The  stones  shall  be  laid  in  full  mortar  beds, 
well  bonded  with  each  other  and  with  the  face  stone,  and  with  all 
spaces  filled  with  small  stones  and  spalls,  well  grouted. 

No  stone  shall  be  cut  on  the  wall,  and  stones  once  bedded  shall 
not  be  removed  unless  directed  by  the  engineer. 

The  foundation  course  shall  be  of  large  stones  not  less  than  12 
inches  in  thickness  and  8  feet  area  of  bed,  and  when  the  wall  is  4 
feet  or  less  in  thickness  shall  extend  from  front  to  back. 

The  mortar  employed  for  second-class  masonry  will  be  of  Rosen- 
dale  cement,  in  the  proportion  of  1  of  cement  to  2  of  sand.  Portland 
cement  will  be  used  wherever  directed  by  the  engineer. 

958.  Third-class  Masonry. — Masonry  of  this  class  will  generally 
be  used  for  box  culverts,  retaining  and  slope  walls,  and  for  back- 
ing for  first-class  masonry.    It  shall  consist  of  sound  stones  laid  on 
their  natural  beds,  and  roughly  squared  .where  used  for  face  work. 

The  walls  shall  be  carried  up  in  courses  ranging  from  15  to  18 
inches  in  height;  each  course  shall  be  well  bonded,  having  a  header 
at  every  3  feet.  Not  more  than  one  third  of  the  stones  shall  be  less 
than  9  inches  thick,  or  contain  less  than  two  cubic  feet,  and  no 
•stone  shall  be  less  than  6  inches  thick.  The  stones  shall  be  laid  in 
Rosendale  cement  mortar,  and  each  course  well  grouted. 

959.  Fourth -class  Masonry  will  consist  of  stone  laid  dry,  and 
will  be  used  for  box  culverts,  retaining,  slope,  breast,  and  parapet 
walls,  and  paving  of  box  and  arch  culverts. 

960.  First-class  Arch-culverts  shall  be  built  in  accordance  with 
the  specifications  for  first-class  masonry,  with  the  exception  of  the 
arch  sheeting  and  ring-stones.     The  ring-stones  shall  be  so  dressed 
that  when  laid  their  beds  will  radiate  truly  from  the  centre  of  the 
circle.     The  ring-stones  and  sheeting  shall  not  be  of  less  thickness 


G66  HIGHWAY    CONSTRUCTION. 

than  10  inches  on  the  soffit,  and  shall  be  dressed  the  full  depth  of 
the  bed,  so  as  to  form  joints  not  exceeding  three  eighths  of  an  inch ; 
each  stone  must  break  joints  with  its  fellow  by  at  least  10  inches. 
Arch  stones  to  be  full  bedded  in  mortar,  and  each  course  afterwards 
thoroughly  grouted.  The  face  stones  to  be  rock-face,,  with  a  one- 
inch  chisel-draught  around  the  edges. 

961.  Second-class  Arch-culverts. — Arch-culverts  of  8  feet  span 
and  under  shall  be  constructed  of  suitable  flat  bedded  stones,  rang- 
ing, according  to  the  span,  from  16  to  24  inches  deep,  and  with  a 
minimum  length  of  from  16  to  24  inches,  and  5  to  6  inches  IT. 
thickness  on  the  soffit.     They  must  invariably  extend  through  the 
entire  thickness  of  the  arch;  each  stone  to  be  well  and  closely  fitted 
so  as  to  give  half -inch  joints,  and  to  break  joints  %with  its  fellow  9 
to  7  inches.    The  whole  to  be  laid  in  thin  cement  mortars,  and  each, 
course  well  grouted  immediately  after  being  laid. 

The  face-stones  of  the  arch  to  be  as  nearly  uniform  in  depth  as- 
possible,  of  large  size,  and  neatly  incorporated  with  the  perpendicu- 
lar face  of  the  masonry.  The  keystones  to  be  10  or  12  inches  on- 
the  soffit,  to  have  a  chisel-draught  around  their  edges,  and  to  project 
beyond  the  face  of  the  wall  2  or  3  inches.  The  side  and  wing  walls 
will  be  of  second-class  masonry. 

The  extrados  of  all  arches  shall  be  flushed  with  cement  mortar 
three  inches  thick,  levelled  up  and  rounded  to  a  moderately  even 
and  smooth  surface. 

962.  Centring. — Centres  of  arches   must   in  all  cases  be  well 
formed,  of  ample  strength,  securely  placed  in  position,  and  in  every 
respect   conform   to  the  requirements  of  the  engineer.     The  ribs 
must  not  be  placed  further  apart  than  3  feet  in  any  case.     The 
lagging  shall  be  3  inches  thick;   the  supports  of  centres  shall  be 
substantial  and  well  constructed,  and  they  must  be  provided  with 
proper  wedges  for  easing  centres  when  required.     Centres  shall  not 
be  struck  without  permission  from  the  engineer. 

963.  Wing  Walls  will  generally  be  of  first-class  masonry,  laid 
up  in  steps,  each  step  covered  with  a  hammer-dressed  coping. 

964.  Parapets  of  masonry  structures  will  be  of  first-class  ma- 
sonry, covered  with  hammer-dressed  coping. 

965.  Laying  Masonry  in  Freezing  Weather. — Xo  masonry  is  tu 
be  built  in  freezing  weather,  except  by  permission  of  the  engineer. 
If  such  permission  is  given  the  mortar  shall  be  made  by  either  of 
the  following  methods: 


SPECIFICATIONS   AND    CONTRACTS.  66r 


Make  a  mortar  of  one  part  of  hydraulic  lime  and  three  parts  of 
sand,  mix  thoroughly,  and  allow  it  to  stand  in  a  heap  covered  with 
stable  manure  until  used,  to  prevent  freezing. 

Mix  mortar  for  use  with  ordinary  cement  in  the  proportions 
of  one  to  three.  Both  mortars  to  be  saturated  with  brine  in  the 
final  mixing.  Or, 

Dissolve  one  pound  of  rock  salt  in  18  gallons  of  water  when  the 
temperature  is  at  32  degrees  Fahr.,  and  add  one  ounce  of  salt 
for  every  degree  lower  of  temperature,  or  enough  salt,  whatever  the 
temperature  may  be,  to  prevent  the  mortar  freezing. 

No  masonry  laid  in  freezing  weather  to  be  pointed  until 
spring. 

966.  Pointing. — All   outside   joints   of   first-    and  second-class 
masonry  shall   be  raked  out   to  a  depth  of  one  inch,  and  neatly 
pointed  with  a  mortar  made  of  one  part  Portland  cement  and  one 
part  of  sand. 

967.  Grouting. — Each  course  of  masonry  as  laid  shall  be  grouted 
with  a  mixture  of  two  parts  of  cement  to  3  parts  of  sand,  no  more 
water  being  used  tfran  that  necessary  to  give  the  required  fluidity. 

968.  Brick  Masonry. — The   bricks  used  shall   be   of  the   best 
quality,   hard-burned   entirely  through,   regular  and  uniform  in 
shape  and  size.     Soft  or  underburned  bricks  will  not  be  allowed  in 
the  work.     The   bricks  shall  be  laid  in  cement  mortar   made  as 
directed.     Every  brick  shall  be  laid  in  a  full  bed  of  mortar  on  bot- 
tom, sides,  and  ends,  which  for  each  brick  is  to  be  performed  at  one 
operation.     In  no  case  is  the  joint  to  be  made  by  working  in  mortar 
after  the  brick  is  laid.     The  joints  shall  not  exceed  £  of  an  inch., 
and  none  shall  be  less  than  £  of  an  inch,  and  shall  be  neatly  struck 
or  flush-pointed.     Every  sixth  course  to  be  headers.     No  "  bats  " 
shall  be  used  except  in  the  backing  of  walls,  where  a  moderate 
proportion  (to  be  determined  by  the  engineer)   may  be  used,  but 
nothing  smaller  than  half -bricks  will  be  allowed. 

The  bricks  will  be  inspected  and  culled  on  delivery,  and  those 
condemned  must  be  at  once  removed. 

The  bricks  must  be  thoroughly  wet  just  before  laying. 

In  forming  arches  the  bricks  must  be  laid  in  concentric  rings, 
each  longitudinal  line  of  bricks  breaking  joints  with  the  adjoining 
lines  in  the  same  ring  and  in  the  ring  under  it. 

969.  Dry  Walls. — Retaining,  slope,  parapet,  and  breast  walls  oi: 


668  HIGHWAY    CONSTRUCTION. 

dry  stone  will  be  constructed  where  directed.  The  stones  for  this 
class  of  work  must  be  sound,  flat,  bedded  stones.  No  round  or 
cobble  stones  will  be  allowed.  Not  more  than  one  third  of  the 
stones  shall  be  less  than  one  foot  thick,  and  no  stone  shall  be  less 
than  six  inches  thick  or  have  a  bed  area  of  less  than  four  feet.  The 
stones  shall  be  set  horizontally  on  their  largest  bed,  and  so  well 
bedded  and  fitted  as  to  require  neither  spalls  nor  wedges  to  keep 
them  in  place.  All  walls  shall  be  covered  with  a  hammer-dressed 
coping  of  the  dimensions  shown  on  the  plans. 

970.  Dry  Box-culverts. — The  bottom  shall  be  paved  with  good 
sound  stone  closely  set  on  edge  under  the  walls  as  well  as  the  water- 
way.    The  side  walls  shall  be  built  of  large  well-shaped  stones  well 
bonded  and  joints  well  broken.     No  stone  shall  have  a  less  area 
of  face  than  one  square  foot.     There  shall  be  one  header  to  every 
three  stretchers,  and  the  header  must  pass  entirely  through  the 
wall.     The  covering-stones  must  be  entirely  sound  and  wide  enough 
to  extend  at  least  two  thirds  across  either  wall. 

The  end  walls  of  box-culverts  shall  be  laid  up  in  second-class 
masonry  and  finished  off  in  accordance  with  the  plans.  The  coping 
must  be  of  proper  and  uniform  thickness,  neatly  hammer-dressed  on 
top  and  face. 

971.  Pipe-culverts. — Culverts    of    salt-glazed    earthenware    or 
cast-iron  pipe  shall  be  constructed  at  such  points  as  the  engineer 
may  designate.     The  ends  of  said  pipes  will  be  carried  by  head 
walls  of  either  brick  or  stone  masonry  covered  with  stone  coping. 
The  form  and  dimensions  of  these  structures  shall  correspond  to 
the  plans  prepared  therefor. 

The  earthenware  pipe  shall  be  of  the  quality  known  as  culvert- 
pipe.  It  shall  be  sound  and  well  burned  throughout,  free  from 
cracks,  flaws,  fire-checks,  and  other  imperfections,  and  shall  be  of 
uniform  thickness  throughout  and  shall  have  not  less  than  the 
following  weights : 

Internal  diameter.  Weight  per  foot. 

6  inches 15  pounds 

9  «       28 

12  '   40 

15  '   60 

18  '   80 

20  '   90 

24  «  130 


SPECIFICATIONS   AND    CONTRACTS.  (>G<) 

The  joints  shall  be  closed  with  cement-mortar. 

Cast-iron  pipe  shall  be  used  wherever  directed  by  the  engineer, 
and  shall  be  obtained  from  a  foundry  approved  by  him.  It  shall 
be  of  the  diameters  and  thickness  ordered,  will  be  laid  in  the  same 
manner  as  earthenware  pipe,  and  the  joints  calked  with  lead  if  so 
ordered. 

972.  Cement. — All  cement  furnished  must  be  of  some  well  and 
favorably  known  brand,  and  shall  be  approved  by  the  engineer.     It 
shall  be  delivered  in  barrels  or  equally  tight  and  safe  receptacles, 
and  after  delivery  must  be  protected  from  the  weather  by  storing  in 
a  tight  building  or  by  suitable  covering.     The  packages  shall  not  be 
laid  directly  on  the  ground,  but  shall  be  laid  on  boards  raised  a  few 
inches  from  it.     To  insure  its  good  quality  it  shall  be  subjected  to 
the  following  tests,  and  every  cask  or  lot  of  cement  rejected  by  the 
engineer  shall  be  conspicuously  marked  "  condemned,"  and  shall  be 
removed  from  the  site  of  the  works;  and,  after  rejection,  should  any 
of  the  cement  so  rejected  be  found  to  have  been  used,  the  work 
where  it  has  been  used  shall  be  taken  down  and  replaced  with 
cement  of  the  proper  quality  without  extra  compensation. 

The  supply  of  cement  must  be  so  gauged  that  a  sufficient  quan- 
tity will  be  kept  on  hand  to  allow  ample  time  for  the  tests  to  be 
made  without  delay  to  the  wrork  of  construction. 

973.  Cement  Tests. — The  Rosendale  cement  must.stand  a  tensile 
strain  of  50  pounds  per  square  inch  of  sectional  area  on  specimens 
mixed  to  a  stiff  paste  and  allowed  to  set  thirty  minutes  in  air  and 
twenty-four  hours  under  water,  and  of-  00  pounds  on  specimens 
allowed  to  set  seven  days  under  water,  and  shall  be  ninety  per  cent 
fine  when  tried  with  a  sieve  having  '.'500  meshes  to  the  square  inch. 

,  It  must  take  not  less  than  twenty-five  minutes  to  bear  the  light 
wire,  that  is,  a  weight  of  four  ounces  on  a  wire  one  twelfth  of  an 
inch  in  diameter. 

Portland  cement  shall  be  tested  in  the  same  manner  and  the 
requirements  for  fineness  will  be  the  same,  but  specimen  briquettes 
will  be  required  to  resist  without  fracture  a  tensile  strain  of  at 
least  175  Ibs.  per  square  inch  at  the  expiration  of  three  days,  and  at 
the  expiration  of  seven  days  to  show  a.i  increase  of  at  least  50  per 
cent  over  the  strength  at  three  days,  but  it  must  bear  a  minimum 
strain  of  350  Ibs.  per  square  inch  at  the  end  of  seven  days. 

974.  Sand. — The  sand  used  for  making  mortar  shall  be  sharp, 


G70  HIGHWAY    CONSTRUCTION. 

clean,  and  free  from  loam  and  vegetable  matter.  If  sand  of  the 
required  quality  cannot  be  found  in  natural  beds  on  the  line  of  the 
work,  it  shall  be  furnished  by  the  contractor.  The  sand  shall  be 
screened  and  washed  if  so  ordered  by  the  engineer. 

975.  Water. — The  water  employed  for  mortar  shall  be  fresh  and 
clean,  free  from  mud   or  other  objectionable  matter.     Sea-water 
may  be  used  if  permission  is  given  by  the  engineer. 

976.  Mortar  shall  be  composed  of  two  parts  of  sand  and  one 
part  of  cement,  mixed  thoroughly  dry  and  tempered  to  the  required 
consistency. 

When  Used. — It  shall  be  used  as  soon  as  made,  and  any  mortar 
that  may  have  taken  a  "  set"  while  unused  shall  be  wasted. 

Variation  in  Proportion. — No  variation  from  the  above  propor- 
tions will  be  permitted  unless  to  make  the  mortar  richer  when 
required  in  special  cases. 

Tempering. — The  thorough  mixing  and  incorporation  of  the 
materials  will  be  insisted  upon.  The  dry  cement  and  sand  shall  be 
turned  over  and  mixed  with  shovels  by  skilled  workmen  not  less 
than  ten  (10)  times  before  the  water  is  added ;  after  adding  the  water, 
the  paste  shall  be  again  turned  over  a  d  mixed  by  skilled  workmen 
not  less  than  six  (6)  times  before  it  is  nsed. 

Boxes. — Tight  mortar  boxes  will  be  provided,  and  no  mortar 
shall  be  made  except  in  such  boxes. 

977.  Concrete,  how  Composed. — Concrete  shall  consist  of  angular 
fragments  of  sound,  durable  stone  or  hard-burnt  brick,  which  shall 
be  cleaned  and  thoroughly  freed  from  dust  and  dirt,  and  broken  so 
as  to  pass  in  any  direction  through  a  ring  two  (2)  inches  in  diameter, 
and  of  hydraulic  cement  and  sand,  in  the  following  proportions  by 
volume : 

Cement 1  part 

Broken  stone 5  parts 

Sand 2      " 

Mixing. — These  materials  shall  be  intimately  incorporated  on 
the  mixing-board  or  in  a  mechanical  mixer,  and  after  proper  tem- 
pering shall  be  deposited  carefully  in  place  and  thoroughly  rammed 
until  the  surface  is  floated. 

Period  of  Repose. — The  concrete  so  laid  shall  be  left  without 
disturbance  or  shock  for  at  least  twenty-four  (24)  hours. 


SPECIFICATIONS   AND    CONTRACTS,  671 


Variation  in  Proportions. — The  above  proportions  shall  be 
varied  without  extra  compensation  upon  the  order  of  the  engineer 
and  to  his  entire  satisfaction. 

Expedition*  Operation.— Tine  whole  operation  of  mixing  and 
laying  each  batch  of  concrete  shall  be  performed  as  expeditiously 
as  possible,  with  the  use  of  a  sufficient  number  of  skilled  men. 

978.  Foundation   Excavation. — Foundation-pits    shall    be    ex- 
cavated to  such  depths  as  the  engineer  may  deem  proper  for  the 
safety  and  permanence  of  the  structure  to  be  erected. 

979.  Artificial    Foundations. — Foundations    of    piles,    timber, 
plank,  and  concrete  shall  be  prepared  of  such  dimensions  and  in 
such  manner  as  the  engineer  may  direct,  and  the  materials  used 
shall  conform   in  quality,  etc.,  to  the  requirements  stated  for  the 
respective  kinds. 

980.  Timber. — The  timber  furnished  shall  be  sound,  straight- 
grained,  well  seasoned,  and  free  from  sap,  large  knots,  shakes,  and 
wanes.     Knotty  timber  will  not  be  allowed  in  the  work  where  such 
would  impair  its  strength. 

981.  Piles. — The  piles  shall  be  of  sound,  straight-grained  tim- 
ber from  which  the  bark  has  been  removed;   they  shall  measure 
not  less  than   8  inches  in  diameter  at  the  small  end,  nor  be  less 
than  28  feet  long.    They  may  be  driven  with  any  approved  form  of 
pile-driver  or  by  the  "  hydraulic  jet:"  if  they  are  driven  by  this 
latter  method,  they  shall  be  constantly  loaded  with  a  weight  of 
2000  Ibs.     They  shall  be  driven,  by  whichever  method  adopted, 
until  they  do  not  move  more  than  one-half  inch  under  the  blow  of 
a  hammer  weighing  2000  Ibs.  and  falling  30  feet. 

982.  Cofferdams. — Where  cofferdams  are  required  for  founda- 
tions, they  shall  be  constructed  in  the  manner  directed  by  the 
engineer,  and  all  pumping,  bailing,  and  draining  shall  be  performed 
as  required  and  directed  by  the  engineer. 

983.  Wrought-iron.— All  wrought-iron  work  furnished  to  be  of 
the  specified  form  and  dimensions.     The  wrought-iron  used  shall 
be  the  best  refined  iron;  it  shall  be  tough,  close-grained,  highly 
fibrous,  and  when  broken  shall  show  a  blue-gray  fracture.     It  shall 
bear  a  high  welding  heat,  and  a  cold  bar  must  bend  through  90  de- 
grees without  sign  of  fracture;  the  tensile  strength  to  be  not  less 
than  50,000  Ibs.  per  square  inch  of  sectional  area  when  tested  in  large 
and  long  lengths.     The  reduction  of  breaking  area  shall  average.  25 


672  HIGHWAY   CONSTRUCTION. 

per  cent,  and  the  elongation  of  the  bar  before  rupture  shall  be  at 
least  15  per  cent.  Iron  subjected  to  compressive  strain  to  have  an 
elastic  limit  of  not  less  than  25,000  Ibs.  per  square  inch. 

984.  Cast-iron. — All  cast-iron  work  to  be  of  the  specified  form 
and  dimensions;  the  iron  to  be  gray  iron,  of  uniform  color  and 
structure,  with  medium  grain,  sharp  bright  fracture,  tough  texture, 
and  a  low  percentage  of  graphite.  It  shall  be  clean  and  free  from 
sand,  scoria,  cold-shuts,  blow-holes,  blisters,  or  other  injurious  de- 
fects. Sample  pieces  1  inch  square,  cast  from  the  same  heat  of 
metal  in  sand-moulds,  shall  be  capable  of  sustaining,  on  a  clear  span 
of  4  feet  8  inches,  a  central  load  of  500  pounds  when  tested  in  a 
rough  bar.  A  blow  from  a  4-pound  hand  hammer  shall  produce  an 
indentation  on  a  rectangular  edge  of  the  casting  without  flaking 
the  metal. 

GENERAL   STIPULATIONS    APPLICABLE   TO   ALL   CONTRACTS. 

The  following  stipulations  are  applicable  to  all  classes  of  work 
and  should  be  inserted  in  all  specifications,  being  varied,  of  course, 
to  suit  each  particular  case. 

985-  Interpretation  of  Specifications. — In  case  of  ambiguity  of 
expression  in  the  specifications,  or  doubt  as  to  the  correct  interpre- 
tation of  the  same,  the  matter  shall  be  submitted  to  the  engineer, 
whose  decision  shall  be  final. 

986.  Omissions  in  Specifications. — Any  work  or  materials  that 
may  have  been  accidentally  omitted  in  the  description  of  the  work, 
but  which  is  clearly  implied,  shall  be  furnished  by  the  contractor 
the  same  as  if  it  had  been  specifically  stated. 

987.  Engineer  defined. — Wherever  the  word  "engineer"  is  used 
it  refers  to  the  chief  engineer  or  his  authorized  assistants,  by  whom 
all  explanations  and  directions  necessary  for  the  satisfactory  pros- 
ecution and  completion  of  the  work  described  in  these  specifica- 
tions will  be  given. 

988.  Contractor  defined. — Wherever  the  word  "contractor"   is 
used  it  refers  to  and  means  the  party  or  parties  who  shall  have  duly 
entered  into  .contract  with  the  of  to  perform 
the  work;  their  duly  authorized  agents  or  legal  representatives. 

989.  Notice  to  Contractor. — Any  written  notice  to  the  contractor 
which  may  be  requisite  under  these  specifications  may  be  served  on 


SPECIFICATION'S   AND    CONTRACTS.  673 

said  contractor  either  personally  or  by  mail,  or  by  leaving  the  samq 
at  his  last  known  place  of  residence. 

990.  Preservation   of  Engineer's  Marks,   etc. — All   engineer  s 
marks  and  stakes  after  location  shall  be  carefully  preserved  with- 
out disturbance  until  permission  for  their  removal  or  erasure  shall 
be  given,  and  every  facility  must  be  furnished  for  the  staking  out, 
etc.,  of  all  work  to  be  done  under  these  specifications. 

991.  Dismissal  of  Incompetent  Persons. — Any  incompetent  per- 
son or  persons  who  may  be  employed  on  the  work  shall  be  removed 
on  the  requisition  of  the  engineer;  and  no  person  so  removed  shall 
thereafter  be  employed  upon  any  portion  of  the  work. 

992.  Spirituous  Liquors. — Contractors' are  not  to  give  or  sell  or 
suffer  any  one  to  give  or  sell  or  keep  any  ardent  spirits  on  any  part 
of  the  work  or  in  any  boarding-house  or  building  under  his  control. 

993.  duality  of  Materials. — All  materials  furnished  and  used 
under  these  specifications  must  be  of  the  best  quality  of  their  re- 
spective kinds,  free  from  any  and  all  defects  which  in  the  judg- 
ment of  the  engineer  may  render  them  unfit  for  use.     Eejected 
material  must   be   at   once    removed    from    the    works    or    con- 
spicuously marked  "  condemned."     If  condemned  material  is  used 
in  any  part  of  the  work,  the  same  shall  be  removed  and  replaced 
with  materials  of  the  quality  required  by  these  specifications. 

994.  Samples. — Before  any  materials  are  used,  samples  thereof 
shall  be  furnished  the  engineer  by  the  contractor.    Said  samples,  if 
approved,  shall  remain  in  the  engineer's  office   and  be  used  as  the 
standard  with  which  all  like  materials  furnished  under  these  speci- 
fications must  agree. 

995.  Deviations  from  Plans  and  Specifications. — No  deviations 
from  the  specifications  or  detailed  plans  will  be  allowed,  unless  a 
written  permission  shall  have  been  previously  obtained  from  the 
engineer. 

996.  Right   reserved  to  alter    Details. — The  engineer,  during 
the  progress  of  the  work,  may,  by  giving  written  notice  to  the  con- 
tractor, alter  any  of  the  details  of  construction  in  any  manner  that 
may  be  found  expedient  or  suitable ;  such  alterations  shall  not  in- 
validate the  contract,  and  the  contractor  must  adopt  and  execute 
the  same  as  if  they  were  part  of  the  original  contract,  and  at  the 
completion  of  the  work  an  allowance  will  be  made  for  such  alter- 
ations, etc.,  either  for  or  against  the  contractor  as  the  case  may  be, 
-and  the  value  of  such  alterations  will  be  estimated  by  the  engineer 


674  HIGHWAY   CONSTRUCTION. 

from  the  schedule  of  prices  attached  to  the  contract,  or  should  it 
not  apply,  the  equitable  amount  will  be  estimated  by  the  engineer. 

997.  Inspectors. — The  work  under  these  specifications  is  to  be 
prosecuted  at  and  from  as  many  different  points  on  the  line  of  the 
work  as  the  engineer  may  from  time  to  time  determine,  and  at  each 
of  said  points  inspectors  may  be  placed  on  the  day  designated  for 
the  commencement  of  the  work  thereat.     Whenever  any  work  is  in 
progress  at  or  from  one  or  more  points  at  a  time,  an  inspector  may 
be  appointed  by  the  engineer  to  supervise  each  subdivision  of  the 
same,  viz.,  for  the  inspection  of  the  material,  excavation,  prepara- 
tion for  the  foundation,  the  laying  of  the  pavement,  etc. 

998.  Defective  Work. — The  contractor  will  be  held  responsible 
for  the  faithful  execution  of  the  work  in  accordance  with  the  speci- 
fications. Any  defective  work  that  may  be  discovered  by  the  engineer 
or  his  appointees  before  the  final  acceptance,  or  before  final  pay- 
ment shall  have  been  made,  shall  be  removed  and  replaced  by  work 
and  materials  which  shall  conform  to  the  spirit  of  the  specifica- 
tions; the  fact  that  the  inspector  or  other  person  in  charge  may 
have  overlooked  such  defective  work  shall  not  constitute  an  ac- 
ceptance of  the  same. 

999.  Measurements. — The  different  classes  of  work  will  be 
measured  as  follows : 

Clearing  and  grubbing  by  the  acre. 

Excavation  in  all  classes  of  earth,  rock,  etc.,  and  in  all  situations, 
including  ditches,  foundations,  altering  the  channel  of  water- 
courses, borrow-pits,  etc.,  by  the  cubic  yard;  the  measurement 
shall  invariably  be  made  in  excavation.  If  any  case  should  arise 
where  this  may  be  found  impossible,  then  the  engineer  shall  deter- 
mine the  quantities,  making  all  proper  allowances,  of  which  he  vrJ3 
be  the  judge. 

Overhaul.— The  contract  price  of  excavation  shall  be  tatoa  $e> 
include  the  whole  cost  of  hauling,  except  only  extreme  cases  whioh 
may  involve  a  haul  of  more  than  eight  hundred  (800)  feel, 
every  hundred  feet  over  eight  hundred  (800)  and  up  to 
hundred  (2500)  the  contractor  will  be  allowed  at  the  rate  of  one 
cent  per  cubic  yard ;  that  is  to  say,  in  the  event  of  the  haul  being 
in  any  case  2500  feet,  seventeen  cents  (17)  per  yard  will  be  added 
to  the  schedule  rate,  and  will  be  the  maximum  allowance  for  over- 
haul in  any  case. 


SPECIFICATIONS   AND    CONTRACTS.  675 

Tlie  price  stipulated  for  excavation  of  the  several  denominations, 
together  with  the  price  of  overhaul  in  extreme  cases,  shall  be  the 
tola";  price  for  excavating,  loading,  removing,  depositing,  and  shap- 
ing all  the  material.  In  a  word,  the  rates  and  prices  stipulated  in 
the  contract  must  be  understood  to  cover  every  contingency, — the 
furnishing  of  all  labor,  material,  power,  and  plant,  the  cost  of  finish- 
ing up  cuttings  and  embankments,  the  dressing  and  draining  of 
borrow-pits,  and  the  dressing  of  slopes  to  the  required  angle,  and 
the  completing  of  everything  connected  with  the  grading  in  a 
creditable  and  workmanlike  manner,  in  accordance  with  the  direc- 
tions and  to  the  satisfaction  of  the  engineer. 

Masonry  of  all  kinds  and  classes  (stone  and  brick)  by  the  cubic 
yard  in  place. 

Timber,  lumber  and  plank,  of  all  kinds  and  for  all  purposes,  by 
the  foot,  board  measure,  in  place. 

Piles  by  the  lineal  foot  in  place. 

Culvert  aiid  Drain-pipe  of  all  classes  by  the  lineal  foot  in 
place. 

Stone,  Brick,  and  Pole  Drains  by  the  lineal  foot  in  place. 

Concrete  by  the  cubic  yard  in  place. 

Curbing  by  the  lineal  foot  in  place. 

Gutters  by  the  square  foot  in  place. 

Crossing  or  Bridge  8 tones  by  the  square  foot  in  place. 

Catch-basins  by  number  as  completed,  including  all  appurte- 
nances and  connections. 

Bridges  by  the  lineal  foot  in  place. 

Pavements. — All  classes  of  pavements  will  be  measured  by  the 
square  yard  in  place ;  and  the  area  occupied  by  the  rails  of  street 
railways  will  be  deducted,  but  the  space  occupied  by  manhole 
heads  and  catch-basins,  when  not  exceeding  one  square  yard  each,. 
*#ill  be  included. 

The  several  measurements  will  be  made  and  computed  by  the 
engineer,  and  his  final  return  of  the  several  amounts  shall  be  the 
only  Yaiid  account  of  the  work  done  and  materials  furnished.  All 
previous  estimates  upon  which  partial  payments  may  have  been 
made  are  merely  approximate,  and  subject  to  the  correction  of  the- 
rmal return. 

1000.  Partial  Payments. — Monthly  estimates  shall  be  made 
during  the  progress  of  the  work,  and  payments  to  the  amount  of  80 


676  HIGHWAY   CONSTRUCTION. 

per  cent  thereof  will  be  made,  the  retained  percentage  not  being 
due  or  payable  until  the  final  completion  of  the  work.  These 
monthly  estimates  do  not  constitute  an  acceptance  of  the  work, 
the  final  estimate  and  formal  acceptance  constituting  the  only 
valid  acceptance  of  the  whole  or  any  part  of  the  work. 

1001.  Commencement  of  the  Work. — The  work  to  be  done  under 
these  specifications  shall  be  commenced  on  such  day  and  at  such 
place  or  places  as  the  engineer  may  direct.     Failure  to  so  commence 
without  a  good  and  valid  reason  therefor  will  be  authority  for  the 

to  declare  the  contract  forfeited,  and  the  said  may 

proceed  with  the  execution  of  the  work  in  such  manner  as  may  be 
deemed  proper. 

1002.  Time  of  Completion.— The  work  shall  be  prosecuted  in 
such  manner  as  to  complete  it  in  accordance  with  the  specifications 
on  or  before  the  expiration  of  working  days.     Should  the 
execution  of  the  work  be  delayed  in  consequence  of  any  act  or 
omission  on  the  part  of  the                ,  the  condition  of  the  weather, 
or  by  any  circumstances  so  unusual  that  they  could  not  be  foreseen 
previous  to  or  avoided  during  the  construction  of  the  work  (all  of 
which  shall  be  determined  by  the  engineer,  who  shall  certify  the 
same  in  writing),  the  time  during  which  the  work  was  so  suspended 
shall   be  excluded,   and   the  time   extended   by  a   corresponding 
number  of  days. 

But  neither  an  extension  of  time  for  any  reason  beyond  the 
date  fixed  for  the  completion  of  the  work,  nor  the  acceptance  of  any 
part  of  the  work  comprised  in  these  specifications  subsequent  to 
the  said  date,  shall  be  deemed  to  be  a  waiver  by  the  said 
of  the  right  to  abrogate  the  contract  for  abandonment  or  delay  in 
the  manner  herein  provided. 

1003.  Progress  of  Work  and  Forfeiture  of  Contract.  —  The 
reserves  the  right  to  declare  the  contract  forfeited,  if  at 

any  time  it  should  appear  to  the  engineer  that  the  work  or  any  part 
thereof  is  being  unnecessarily  delayed,  or  that  the  contractor  is 
wilfully  violating  any  of  the  conditions  of  the  contract,  or  is  exe- 
cuting the  same  in  bad  faith,  or  if  the  said  work  be  not  fully  com- 
pleted within  the  time  named  for  its  completion;  he  shall  have 
power  to  notify  the  contractor  to  discontinue  all  work  or  any  part 
thereof,  by  a  written  notice  to  be  served  upon  the  contractor  either 
personally  or  by  leaving  said  notice  at  his  residence  or  with  his 


SPECIFICATIONS  AND   CONTRACTS.  677 

agent  in  charge  of  the  work.  And  thereupon  the  contractor  shall 
discontinue  said  work  or  such  part  thereof,  and  the  engineer  shall 
thereupon  have  the  power  to  place  such  and  so  many  persons  as  he 
may  deem  advisable,  by  contract  or  otherwise,  to  complete  the  work, 
or  such  part  thereof,  and  to  use  such  materials  as  he  may  find  upon 
the  line  of  said  work,  and  to  procure  other  materials  for  the  com- 
pletion of  the  same,  and  to  charge  the  expense  of  said  labor  and 
materials  to  the  aforesaid  contractor;  and  the  expense  so  charged 
shall  be  deducted  and  paid  by  the  ,  out  of  such  moneys  as 

may  be  then  due,  or  may  at  any  time  thereafter  become  due  said 
contractor  on  account  of  work  performed  under  these  specifica- 
tions; and  in  case  such  expense  is  less  than  the  sum  which  would 
have  been  payable  if  the  same  had  been  completed  by  the  said  con- 
tractor, he  shall  forfeit  all  claim  to  the  difference ;  and  in  case  such 
expense  shall  exceed  said  sum,  he  shall  pay  the  amount  of  such 
excess  to  the  .. 

1004.  Damages  for  Non-completion. — The  contractor  shall  pay 
to  the  ,  as  damages  for  non-completion  of  the  work  within 
the  time  stipulated  'for  its  completion,  the  sum  of  $100  for  each 
and  every  day  which  may  exceed  the  said  stipulated  time  for  its 
completion,  which  said  sum  of  $100  per  day  is  hereby,  in  view  of 
the  difficulty  of  estimating  such  damages,  agreed  upon,  fixed,  and 
determined  by  the  contractor  and  the  as  the  liquidated 
damages  that  the                will  suffer  by  reason  of  such  default,  and 
not  by  way  of  penalty ;  and  the                is  hereby  authorized  to  de- 
duct said  sum  of  $100  per  day  from  the  moneys  which  may  be  due 
or  become  due  said  contractor  for  work  under  these  specifications. 

1005.  Evidence  of  the  Payment  of  Claims. — In  case  of  any  legal 
claims  being  filed  with  the  against  the  contractor  for  labor 
or  materials  furnished  under  these  specifications,  the  said 

shall  retain  the  whole  or  so  much  of  such  moneys  as  may  be  due 
or  to  become  due  the  contractor  as  may  be  considered  necessary  to 
meet  the  lawful  claims  of  such  persons,  until  the  liabilities  shall  be 
fully  discharged  and  such  notice  withdrawn. 

.1006.  Protection  of  Persons  and  Property. — The  contractor  shall 
during  the  progress  of  the  work  use  all  proper  precautions  by  good 
and  sufficient  barriers,  guards,  temporary  bridges,  etc.,  for  the  pre- 
vention of  accidents,  and  at  night  he  will  put  up  and  keep  suitable 
and  sufficient  lights,  and  he  will  indemnify  and  save  harmless  the 


678  HIGHWAY   CONSTRUCTION. 

against  and  from  all  suits  and  actions,  of  every  name  and 
description,  brought  against  it,  and  all  costs  and  damages  to  which 
the  said  may  be  put  for  or  on  account  or  by  reason  of  any 

injury  or  alleged  injury  to  the  person  or  property  of  another, 
resulting  from  negligence  or  carelessness  of  the  contractor,  his 
agents  or  employees,  in  the  performance  of  the  work,  or  in  guarding 
the  same,  or  from  any  improper  materials  used  in  its  prosecution, 
or  by  or  on  account  of  any  act  or"  omission  of  the  contractor,  his 
agents  or  employees;  and  the  shall  retain  the  whole  or  so 

much  of  the  moneys  due  or  to  become  due  by  reason  of  the  work 
under  these  specifications  as  may  be  considered  necessary,  until  all 
such  suits  or  claims  for  damages  as  aforesaid  shall  have  been  settled 
and  satisfactory  evidence  to  that  effect  is  furnished. 

1007.  Bond  for  Faithful  Performance  of  the  Work.— The  con- 
tractor shall  execute  with  his  sufficient  sureties  a  bond  in  the  sum 
of  thousand  dollars  for  the  faithful  performance  of  the 
work  in  accordance  with  the  requirements  of  the  specifications. 

1008.  Power  to  Suspend  Work.— The  prosecution  of  the  work 
may  be  suspended  for  such  periods  as  the  engineer  may  from  time 
to  time  determine.    No  claim  or  demand  shall  be  made  by  the  con- 
tractor for  damages  by  reason  of  such  suspensions  in  the  work,  but 
the  period  of  such  suspensions  will  be  excluded  in  computing  the 
time  limited  for  the  completion  of  the  work.     During  such  sus- 
pensions all  materials  delivered  upon  but  not  placed  in  the  work 
shall  be  neatly  piled  or  removed  so  as  to  not  obstruct  public  travel. 
The  wages  of  watchmen  retained  for  the  public  protection  during 
the  period  of  suspension  will  be  allowed. 

1009.  Loss  and  Damage. — All  loss  and  damage  arising  out  of 
the  nature  of  the  work  to  be  done  under  these  specifications,  or 
from  any  unforeseen  obstructions  or  difficulties  which  may  be  en- 
countered in  the  prosecution  of  the  same,  or  from  the  action  of  the 
elements,  or  from  incumbrances  on  the  line  of  the  work,  shall  be 
sustained  by  the  contractor. 

1010.  Miscellaneous  Work. — If  any  work  or  service  be  required 
to  be  done  which  in  the  opinion  of  the  engineer  does  not  come 
within  the  class  of  work  to  be  measured  under  the  contract,  he 
shall  be  at  liberty  to  direct  the  contractor  to  perform  the  same  by 
day's  labor,  and  the  contractor  when  required  by  him  shall  furnish 
such  force  and  materials  and  perform  such  work  in  the  manner 


SPECIFICATIONS   AND   CONTRACTS.  679 

directed,  and  he  shall  be  paid  the  reasonable  and  actual  wages  of 
the  men  as  ascertained  by  the  timekeeper  and  the  actual  value  of 
all  materials  furnished,  together  with  fifteen  per  cent  of  the  total 
amount  for  the  use  of  tools  and  profit.  The  engineer  shall  be  at 
liberty  to  discharge  any  inefficient  or  unsuitable  workmen  who  may 
be  placed  on  such  work,  and  the  work  so  performed  will  be  subject 
to  his  approval  before  payment  is  made  therefor. 

1011.  Cleaning  up. — All  surplus  materials,  earth,  sand,  rubbish, 
and  stones,  are  to  be  removed  from  the  line  of  the  work  as  rapidly 
as  the  work  progresses.     At  any  time  within  one  month  after  the 
completion  of  the  work,  if  so  required  by  the  engineer,  all  material 
shall  be  swept  into  heaps  and  removed  from  the  line  of  the  work ;  and 
unless  this  be  done  by  the  contractor  within  forty-eight  hours  after 
being  notified  so  to  do  to  the  satisfaction  of  the  engineer,  the  same 
shall  be  removed  by  the  ,  and  the  amount  of  the  expense 
thereof  shall  be  deducted  out  of  any  moneys  due  or  to  become  due 
to  the  contractor  under  these  specifications. 

1012.  Personal  Attention. — The  contractor  shall  give  his  per- 
sonal attention  to  the  faithful  prosecution  of  the  work,  shall  not 
sublet  the  same  or  any  part  thereof  without  the  consent  of  the 

,  nor  will  he  assign  by  power  of  attorney  or  otherwise  any 
of  the  moneys  payable  under  these  specifications. 

1013.  Payment  of  Workmen. — The  contractor  shall  punctually 
pay  the  workmen  who  shall  be  employed  on  the  work  comprised  in 
these  specifications,  in  cash  current,  and  not  in  what  is  denominated 
*6  store  "  pay. 

1014.  Prices. — The  prices  stated  by  the  contractor  in  his  tender 
and  stipulated  in  the  contract  must  be  understood  to  cover  every 
contingency,  the  furnishing  of  all  labor,  materials,  power,  and  plant 
which  may  be  required  for  the  performing  and  completing  of  the 
work  described  in  these  specifications  (and  for  maintaining  the 
same  in  good  order  for  a  period  of  six  months). 

1015.  Payments,  when   Made. — The   contractor  shall    not    be 
entitled  to  demand  or  receive  payment  for  any  portion  of  the  work 
done  or  materials  furnished  under  these  specifications  until  the 
same  shall  be  fully  completed  in  the  manner  set  forth,  and  such 
completion  duly  certified  by  the  engineer  in  charge  of  the  work, 
and  until  each  and  every  of  the  stipulations  herein  before  men- 
tioned are  complied  with,  and  the  work  completed  to  the  satisfac- 


GSO  HIGHWAY    CONSTRUCTION. 

tion   of  the  and   accepted   by  ,  whereupon   the= 

will  pay  in  cash,  on  the  expiration  of  days  from  the- 

time  of  acceptance,  the  whole  of  the  moneys  accruing  to  the  con- 
tractor under  these  specifications,  excepting  such  sum  or  sums  of 
money  as  may  be  retained  under  any  of  the  provisions  herein 
contained,  and  such  sums  as  may  have  been  paid  in  the  form  of 
partial  payments  upon  the  monthly  estimates  of  the  engineer. 

FORMS    OF   SPECIFICATIONS. 

The  following  forms  of  specifications  may  be  of  assistance  in 
preparing  specifications  for  different  works. 

1016.  Specifications  for  the  Construction  of  a  Highway  front 
to  in  the  town  of  ,  county  of 

The  following  specifications  are  intended  to  cover  the  methods. 
of  construction  and  the  furnishing-  of  all  the  labor  and  materials. 
necessary  for  the  proper  and  workmanlike  completion  of  the  above- 
named  highways  in  accordance  with  the  plans  on  file  in  the  office 
of  the  engineer,  and  in  accordance  with  such  instructions  relating 
thereto  as  may  from  time  to  time  be  given  by  said  engineer,  or  his- 
assistants  and  inspectors. 

Description  of  the  Work.  —  The  character  and  approximate. 
amounts  of  work  to  be  done  are  as  follows  : 

Earth  excavation  ..................................  cubic  yards 

Loose  rock  excavation  .............................  "  " 

Solid      "  "  ............................. 

Embankment  to  be  furnished  from  ..................  "  " 

Borrovv-pits  .....................  '  .................  ,  "  " 

Blind  stone  drains  .................................  lineal  feet 

Tile  drains,  3  inches  in  diameter  ....................  "  " 

6       "       "        "        ....................  "  " 

Earthenware  pipe-culverts,  12'  diameter  .............  "  " 


ti             «        «         24"        "  is        tt 

Dry  box-culverts  ........   .........................  cubic  yards 

"       "        "        ,  third-class  masonry  ...............  "        " 

Dry  retaining-walls  .....    ..........................  "        " 

Rip-rnp  ...........................................  "        " 

Catch-  and  silt-basins,  number  of  .................... 

Paved  gutters  ......................................  lineal    feet 

[Here  insert  the  clauses  suitable  for  each  class  of  work  in  the; 
schedule.] 


SPECIFICATIONS   AND    CONTRACTS.  68  L 

1017.  Specifications  for  Bulkhead  (Fig.  138,  p.  495). 

The  bulkhead  will  be  formed  as  follows : 

The  piles  will  be  of  sound  straight-grained  spruce  or  other 
approved  timber;  they  shall  measure  not  less  than  6  inches  in 
diameter  at  the  small  end  and  not  less  than  12  inches  nor  more 
than  15  inches  at  the  large  end  when  cut  off,  The  piles  shall  have 
the  bark  removed,  be  accurately  pointed,  and  when  required  the 
heads  shall  be  properly  banded  to  prevent  splitting  or  brooming 
while  being  driven;  if  found  necessary,  the  points  shall  also  be  pro- 
tected with  wrought-iron  shoes.  The  piles  will  be  spaced  6  feet 
from  center  to  center,  and  shall  be  driven  with  a  batter  of  1 J  inches 
per  foot.  They  may  be  driven  by  the  hydraulic  "  jet "  or  by  an  or- 
dinary pile-driver;  if  by  the  jet,  they  shall  be  loaded  with  a  weight 
of  2000  pounds.  By  whichever  method  driven,  they  shall  reach  a 
total  penetration  into  the  soil  and  sand  of  not  less  than  15  feet 
below  low- water  mark.  Piles  injured  in  driving  shall  be  drawn  out 
and  replaced  by  sound  ones  at  the  contractor's  expense.  Piles 
found  too  short  shall  be  drawn  out  and  replaced  by  longer  ones. 

Lengthening. — Lengthening  by  using  a  follower  or  blocking 
will  not  be  allowed.  Any  pile  found  too  short  must  be  drawn  out 
and  a  longer  one  substituted.  When  the  piles  shall  have  reached 
the  required  depth,  their  tops  shall  be  sawed  off  evenly  at  the  estab- 
lished grade. 

Pile-cap. — And  thereon  a  pile-cap  of  yellow-pine  timber  ten 
(10)  by  twelve  (12)  inches  will  be  laid,  fastened  to  each  pile  with 
one  one-  (1-)  inch  drift-bolt  eighteen  (18)  inches  long.  On  the  water 
face  and  thirty  (30)  inches  below  the  top  of  the  pile-cap  there  will 
be  placed  a 

Brace  Stick  of  yellow  pine  timber  five  (5)  by  ten  (10)  inches, 
bolted  to  every  second  pile  with  one  one-  (1-)  inch  bolt  eighteen 
(18)  inches  long.  On  the  water  face  at  mean  high-water  mark 
there  will  be  placed  a 

,  Chafing-stick  of  yellow-pine  timber  five  (5)  by  ten  (10)  inches, 
bolted  to  every  pile  with  one  one-  (1-)  inch  bolt.  On  the  land  side 
of  the  piles  at  both  mean  high-  and  low- water  marks  there  will  be 
placed  longitudinally 

Wale-sticks   of  yellow-pine  timber  five  (5)  by  ten  (10)  inches, 
bolted  to  every  pile  with  one  one-  (1-)  inch  bolt. 

Sheet-piling. — On  the  land  side  of  the  wale-sticks  sheet-piling 


682  HIGHWAY   CONSTRUCTION". 

of  tongued  and  grooved  yellow-pine  plank,  three  (3)  inches  thick 
and  not  less  than  eight  (8)  inches  wide,  will  be  driven  to  a  depth 
of  not  less  than  ten  (10)  feet  below  low-water  mark.  Each  plank 
will  be  spiked  to  both  wale-sticks  with  two  six-  (6-)  inch  cut  spikes ; 
the  tops  will  be  sawed  off  level  with  the  upper  wale-stick. 

Anchor-piles. — On  the  land  side  and  opposite  every  third  pile 
and  eighteen  (18)  feet  distant  therefrom  an  anchor-pile  not  less 
than  six  (6)  inches  in  diameter  and  ten  (10)  feet  long  will  be  driven 
to  the  angle  shown  on  plan,  to  a  penetration  of  not  less  than  seven 
(7)  feet.  At  the  back  of  the  anchor-piles  there  will  be  placed 
loosely  upon  the  ground  a  brace-stick  of  yellow-pine  timber  five  (5) 
inches  by  ten  (10)  inches. 

Tension-rods. — Tension-rods  made  from  one  and  one  quarter 
(!£)  inch  iron  will  extend  from  front  to  rear  brace-stick,  passing 
through  both  sticks  and  piles;  the  rods  will  be  screwed  on  both 
ends  and  will  have  under  each  nut  on  the  water  face  an  iron  washer 
four  (4)  inches  in  diameter,  cast  to  the  required  angle. 

Bolt-holes.— All  bolt-holes  will  be  bored  with  an  augur  one 
eigth  (|)  of  an  inch  smaller  than  the  diameter  of  the  bolt  they  are 
to  receive. 

Fender-piles. — Fender-piles  eighteen  (18)  inches  in  diameter  at 
the  butt  and  30  feet  long  will  be  driven  at  every  twenty  (20)  feet 
along  the  water  face. 

Lengths  of  Timber. — The  pile-cap,  braces,  and  chafing-sticks 
shall  be  in  lengths  of  not  less  than  eighteen  (18)  feet;  they  shall  be 
arranged  so  as  to  bring  the 

Joints  on  a  pile.  All  joints  shall  be  made  by  a  twelve  (12)  inch 
half -lap  splice  fastened  with  two  seven  eighths  (•£•)  inch  by  fifteen 
(15)  inch  bolts.  Air  bolt-heads  in  pile-cap  will  be  countersunk 
flush  with  the  top.  Iron  washers  will  be  placed  under  all  bolt- 
heads  and  nuts. 

1018.  Specifications  for  Grading,  Macadamizing,  Curbing,  and 
Flagging  Avenue,  from  to  . 

Grading. — The  entire  width  of  the  avenue  is  to  be  regulated 
and  graded  to  sub-grade,  fifteen  (15)  inches  below  finished  grade, 
in  accordance  with  the  grades  and  cross-section  shown  in  plans. 
Such  portions  as  are  above  the  grade  lines  shall  be  excavated,  and 
such  as  are  below  shall  be  filled  in. 

Slopes. — Slopes  in  both  embankment  and  excavation  shall  be 


SPECIFICATIONS  AND    CONTRACTS.  683 


one  and  one  half  (1^)  horizontal  to  one  (1)  vertical  unless  otherwise 
ordered. 

If  the  material  taken  from  the  excavations  is  unsuitable  or  in- 
sufficient to  make  the  embankments,  the  deficiency  shall  be  sup- 
plied by  the  contractor.  The  material  so  furnished  shall  be  good 
clean  earth,  sand,  gravel,  or  broken  rock  and  earth.  If  broken 
rock  is  furnished,  the  proportion  of  earth  and  rock  shall  not  be  less 
than  1  to  1,  and  the  materials  shall  be  so  distributed  that  no  voids 
shall  be  left. 

Any  perishable  matter  that  may  be  found  at  sub-grade  level 
shall  be  removed  and  the  space  filled  in  with  good  material. 

The  sub-grade  surface  shall  be  truly  shaped  and  trimmed  to 
the  required  cross-section,  then  rolled  with  a  roller  weighing  not 
less  than  300  pounds  per  inch  of  run.  The  rolling  will  be  (Continued 
until  the  surface  has  become  firm  and  hard  :  in  no  case  shall  it  be 
less  than  5  hours  per  1000  square  yards.  Such  parts  as  cannot  be 
reached  by  the  roller  shall  be  tamped  with  hand  rammers.  Water 
shall  be  applied  by  sprinkling  in  advance  of  the  roller,  but  an  ex- 
cess must  not  be  used  ;  generally  25  gallons  per  1000  square  yards 
will  be  sufficient. 

On  the  sub-grade  surface  prepared  as  above  described  a  layer  of 
bank  gravel  will  be  spread  to  a  depth  of  nine  inches  and  rolled  con- 
tinuously until  the  depth  is  reduced  to  seven  inches;  on  the  foun- 
dation so  prepared  the  broken  stone  will  be  placed.  Its  finished 
thickness  will  be  eight  inches.  The  stones  will  be  spread  in  two 
layers  :  the  first  layer  will  be  spread  to  a  depth  of  five  and  a  half  inches 
and  rolled  till  the  depth  is  reduced  to  five  inches  ;  water  will  be  applied 
in  advance  of  the  roller,  but  not  in  excess.  When  the  broken  stone 
is  so  compacted  a  layer  one  inch  thick  of  clean  sand,  or  sand  contain- 
ing not  more  than  15  per  cent  of  loam,  will  be  spread  over  the  sur- 
face, and  the  rolling  continued  until  the  stones  cease  to  sink  or  creep 
in  front  of  the  roller,  and  the  thickness  of  the  layer  of  broken  stone 
is  4  inches  or  thereabouts.  When  the  first  layer  has  been  finished 
to  the  satisfaction  of  the  engineer,  the  second  layer  will  be  spread 
to  the  same  depth  and  treated  in  the  same  manner  as  the  first  layer. 
The  rolling  of  this  surface  will  be  continued  until  all  settlement  has 
wased. 

In  quality  the  stone  must  conform  to  the  sample  in  the  office  of 
the  engineer. 


C84  HIGHWAY    CONSTRUCTION. 

In  form  it  shall  be  as  nearly  cubical  as  practicable,  and  in  size 
shall  not  exceed  in  any  dimension  two  and  a  half  inches,  but  may 
range  fiom  this  size  down  to  quarter-inch  chips;  but  the  proportion 
ut'  stones  below  one  and  a  half  inches  shall  not  exceed  20  per  cent  of 
the  whole  quantity.  Ihe  stone  will  not  be  screened,  but  shall  be 
delivered  as  it  comes  from  the  breakers;  care,  however,  being  taken 
that  clay  does  not  become  intermixed  with  the  stone. 

Gutters. — For  a  width  of  two  feet  on  each  side  of  the  carriage- 
way adjoining  the  curb  a  gutter  of  granite  blocks  will  be  laid. 
Each  block  shall  measure  not  less  than  six  nor  more  than  nine 
inches  in  length,  in  width  not  less  than  three  nor  more  than  five 
inches  in  depth,  not  less  than  seven  nor  more  than  eight  inches; 
the  blocks  to  be  split  and  dressed  so  as  to  form,  when  laid,  close 
joints  on  sides  and  ends. 

The  blocks  will  be  laid  in  courses  parallel  to  the  curb.  Each 
course  shall  be  formed  with  blocks  of  a  uniform  width  and  depth, 
and  laid  so  that  all  the  longitudinal  joints  shall  be  broken  by  a  lap 
of  at  least  two  inches'. 

The  blocks  will  be  laid  on  the  gravel  foundation  and  set  stone 
to  stone,  both  on  sides  and  ends.  When  thus  laid,  their  surface 
shall  be  covered  with  a  layer  of  clean  sharp  sand,  which  shall  be 
swept  with  brooms  until  all  the  joints  are  filled.  Into  the  sand 
joints  thus  made  there  will  be  poured  a  hot  mixture  of  coal  pitch, 
and  creosote.  The  whole  surface  of  the  blocks  will  then  be  covered 
with  one  half-inch  of  sharp  sand,  which  shall  be  left  undisturbed 
until  ordered  removed  by  the  engineer. 

Curbing. — The  curbstones  shall  be  of  bluestone,  equal  in  quality 
to  the  best  North  River  bluestone.  The  curbstones  shall  be  not  less 
than  three  feet  in  length,  five  inches  thick,  twenty  inches  deep,  and 
matched  width  throughout.  The  top  of  the  stone  shall  be  cut  to  a 
bevel  of  one  inch ;  the  front  shall  be  cut  smooth  and  to  a  fair  line, 
to  a  depth  of  fourteen  inches.  The  ends  from  top  to  bottom  shall  be 
truly  squared,  so  as  to  form  close  and  even  joints,  and  the  front  so- 
laid  as  to  present  a  fair  and  unbroken  line.  Curbstones  shall  be 
back  filled,  and  backed  up  with  at  least  one  foot  of  clean,  gritty 
earth,  free  from  clay  and  loam. 

Circular  Corners. — The  curbstones  at  the  corners  of  intersect- 
ing streets  shall  be  cut  on  a  curve,  with  true  and  even  joints,  and 


SPECIFICATION'S   AND    CONTRACTS.  C85 

shall  be  of  the  same  description  as  the  curb  before  described,  and 
be  laid  in  the  same  manner. 

Flagging. — All  the  nagging  to  be  of  bluestone  equal  in  quality 
to  the  best  North  River  bluestone,  even  on  its  face,  and  to  measure 
not  less  than  two  feet  wide,  to  contain  not  less  than  eight  superficial 
feet,  and  to  be  in  no  place  less  than  three  inches  thick.  To  be  laid 
with  close  joints,  in  regular  courses  of  four  feet  wide.  Each  stone 
shall  be  chisel-dressed  on  the  four  edges  a  distance  of  one  inch 
down  from  the  top  and  square  with  the  face  thereof,  and  free  from 
drill-holes. 

Flagging  shall  be  bedded  in  four  inches  of  clean,  gritty  earth  or 
steam  ashes,  free  from  clay  and  loam,  and  the  work  brought  to  an 
even  surface;  the  joints  of  the  nagging  shall  be  closed  up  with 
cement  mortar,  and  be  left  clean  on  the  surface ;  the  whole  space  of 
the  sidewalks  to  be  regulated  before  laying  the  flagging. 

Catch-basins. — Catch-basins  will  be  constructed  -  at  the  points 
indicated  on  the  plans  or  wherever  the  engineer  may  direct. 

They  will  be  of  brick  masonry,  built  with  care,  of  the  form  and 
dimensions  shown  on  the  plan.  They  will  be  made  perfectly  water- 
tight by  plastering  the  interior  with  neat  Portland-cement  mortar  oive 
half -inch  thick.  The  exterior  shall  be  coated  with  cement  mortar 
one  inch  in  thickness.  Each  basin  will  be  connected  by  a  nine-inch 
cement  or  earthenware  pipe-shoot  connected  to  a  twelve-inch  cement 
or  earthenware  pipe.  This  pipe  will  be  laid  on  the  lines  and  grades 
given  by  the  engineer,  and  connected  to  the  sewer  or  other  outlet. 

Each  basin  will  be  fitted  and  furnished  with  a  cast-iron  head 
and  grating  of  the  form  and  dimensions  shown  on  plan. 

(Here  insert  such  clauses  for  general  specifications  and  stipula- 
tions as  are  suitable.) 

1019.  Specifications  for  the  Supply  of  Broken  Stone. — The 
stone  shall  be  fully  equal  to  the  sample  in  the  engineer's  office, 
otherwise  it  will  be  rejected. 

It  shall  be  broken  in  as  nearly  cubical  form  as  practicable,  each 
cube  to  have  a  square  face  and  sharp  edges,  and  shall  not  exceed 
in  any  dimension  two  inches,  but  the  stones  may  range  from  this 
size  down  to  quarter-inch  chips;  but  the  proportion  of  stones  below 
one  and  a  half  inches  shall  not  exceed  20  per  cent  of  the  whole 
quantity. 

The  broken  stones  shall  not  be  screened,  but  will  be  delivered  as 


C8G  HIGHWAY   CONSTRUCTION. 

they  come  from  the  breakers;  care,  however,  being  taken  that  clay 
does  not  become  intermixed  with  them. 

The  stone  when  delivered  must  be  clean  and  free  from  clay  or 
other  dirt. 

The  stone  shall  be  supplied  on  the  order  of  the  engineer  in  such, 
quantities  as  he  may  specify,  and  must  be  delivered  within  the  time 
specified  in  the  order.  Failure  to  so  deliver  the  stone  without  good 
and  sufficient  reason  will  be  a  valid  excuse  for  the  forfeiture  of  the 
contract. 

ADDITIONAL   CLAUSES   REQUIRED   IN   SPECIFICATIONS   FOR 
REPAIRING,   ETC. 

1020.  Indemnification  for  Patent  Claims. — The  contractor  shall 
indemnify  and  save  harmless  the  against  and  from  all  suit& 
and  actions  of.  every  nature  and  description  arising  out  of  the  claim 
or  claims  of  any  person  or  persons  claiming  to  be  patentees  of  any 
process  connected  with  the  work  herein  provided  for,  or  of  any 
materials  used  upon  said  work. 

1021.  Indemnity  Bond. — The  contractor  shall  execute  with  two- 
sufficient  sureties  a  bond  in  the  sum  of  thousand  dollars, 
for  the  indemnification  of  the                against  and  from  all  such 
suits  and  actions  aforesaid. 

1022.  Right  to  Construct  Sewers,  etc. — The  right  to  construct 
sewers  or  any  work  in  connection  therewith,  lay  water,  gas,  or  other 
mains  and  make  house  connections  therewith,  in  advance  of  the 
pavement,  is  expressly  reserved  by  the  ;  and  the  said 

may  suspend  the  work  on  the  pavement  on  any  part  of  the  line  for 
the  purpose  above  stated,  without  other  compensation  to  the  con- 
tractor  for  such  suspension  than  extending  the  time  for  completing 
the  work  as  much  as  it  may,  in  the  opinion  of  the  engineer,  have 
been  delayed  by  such  suspension.  And  the  contractor  shall  not 
interfere  with  or  place  any  impediment  in  the  way  of  any  person 
tir  persons  who  may  be  engaged  in  the  construction  of  such  works. 

1023.  Old  Materials. — All  old  materials  which  it  may  become 
necessary  to  remove,  and  where  no  instructions  for  their  disposal  is 
previously  given,  shall  be  considered  as  the  property  of  the  con- 
tractor, and  the  same  shall  be  immediately  removed  by  him  from 
the  line  of  the  work. 


SPECIFICATIONS   AND    CONTRACTS.  687 

1024.  Security  retained  for   Repairs. — The  shall  re- 
tain out  of  the  moneys  payable  to  the  contractor  on  completion  of 
the  work  the  sum  of  ten  cents  per  square  yard  of  pavement  la*id 
under  these  specifications,  which  sum  of  ten  cents  with  interest  shall 
be  paid  upon  the  expiration  of  the  guaranty  period;  provided  that 
the  work  at  that  time  is  in  good  order,  or  as  soon  thereafter  as  the 
work  shall  have  been  placed  in  good  order,  to  the  satisfaction  of  the 
engineer. 

During  the  guaranty  period  should  any  part  of  the  work  require 
repairs,  the  engineer  shall  notify  the  contractor  to  make  such  re- 
pairs, and  in  case  of  neglect  or  failure  to  make  said  repairs  within 
forty-eight  hours  after  service  of  notice  the  shall  have  the 

right  to  purchase  such  materials  as  may  be  deemed  necessary,  and 
to  employ  such  persons  as  may  be  deemed  proper,  and  to  under- 
take and  complete  such  repairs,  and  to  pay  the  expense  thereof  out 
of  the  said  sum  of  ten  cents  per  square  yard  retained  for  that  pur- 
pose, and  such  part  of  said  sum  as  shall  remain  after  the  expenses 
of  said  repairs  have  been  deducted  will  be  paid  in  the  manner  here- 
inbefore described. 

1025.  Alteration   of  Manhole    Covers,    Stopcock   Boxes,  etc. — 
All  the  frames  and  heads  of  sewer  manholes,  stopcock  boxes  for 
water  and  gas,  are  to  be  adjusted  (either  raised  or  lowered)  to  the 
level  of  the  pavement. 

1026.  Heads  of  Specifications  for  Repaying. 
Specifications  for  Regulating  and  Paving  loith  Pave- 

,  street    „ 

ment  the  Carriageway  of  avenue  ^rom  *° 

(1)  Description  of  the  work. 

(2)  Removal  of  old  materials. 

(3)  Excavation. 

(4)  Adjustment  of  manhole  heads,  etc. 

(5)  Adjustment  of  curb. 

(6)  Adjustment  of  bridge  stone. 

(7)  Furnishing  new  curb. 

(8)  Furnishing  new  bridge  stones. 

(9)  Preparation  of  roadbed. 

(10)  Foundation,  character  of. 

(11)  Concrete. 

(12)  Concrete,  manufacture  and  laying. 


688  HIGHWAY    CONSTRUCTION. 


(13)  Pavement,  character  and  quality. 

(14)  Manner  of  laying. 

(15)  Cleaning  up. 

(16)  Quality  of  material. 

(17)  Inspectors. 

(18)  Eight  to  construct  sewers. 

(19)  Commencement  of  work. 

(20)  Time  of  completion. 

(21)  Suspension  of  work. 

(22)  Extension  of  time. 

(23)  Damages  for  non-completion. 

(24)  Personal  attention  of  contractor. 

(25)  Contractor's  representatives. 

(26)  Defective  work. 

(27)  Improper  prosecution  of  the  work. 

(28)  Accidents  or  damages  to  persons  or  property  to  be  paid  for 
by  the  contractor. 

(29)  Incompetent  workmen. 

(30)  Power  to  annul  contract  for  violation  of  stipulations. 

(31)  Payment  of  claims  for  labor  and  materials. 

(32)  Measurements. 

(33)  Engineer's  estimates. 

(34)  Payments,  when  made. 

(35)  Percentage  retained. 

(36)  Prices. 

(37)  Interpretation  of  specifications. 

(38)  Engineer  defined. 

(39)  Contractor  defined. 

(40)  Preservation  of  engineer  marks,  etc. 

(41)  Indemnification  of  patent  claims. 

(42)  Indemnity  bond. 

(43)  Security  retained  for  repairs. 

1027.  Specifications  for  Street  cleaning  should  Contain  the  fol- 
lowing Conditions. — The  mode  of  cleaning  shall  be  to  first  clean 
the  gutters  of  all  solid  matter,  and  then  sweep  from  the  sides 
towards  the  centre;  dirt  collections  not  to  be  placed  within  5  feet 
of  th<  gutters. 

Whenever  the  sweeping  of  streets  would  cause  the  dust  to  rise, 
they  shall  be  first  sprinkled  by  sprinkling-wagons  to  be  approved 


SPECIFICATIONS   AND   CONTRACTS. 


"by  the  of  the  of  ;  and  the  sprinkling 

rshall  be  so  done  that  the  dust  will  not  be  turned  into  mud. 

All  hand  sweeping  shall  be  done  with  push-brooms,  and  all  sweep- 
Ing  by  machinery  with  machines  appro^  ed  by  the  of 

All  parts  of  streets  covered  with  sheet  asphalt  shall  be  swept  by 
machinery  six  times  each  week,  between  the  hours  of  10  P.M.  and 

6  A.M.,  and  a  sufficient  number  of  men  with  bass  brooms  shall  be 
kept  employed  to  keep  them  constantly  clean  between  the  hours  of 

7  A.M.  and  6  P.M. 

All  accumulations  of  sweepings,  and  of  mud  or  rubbish  removed 
from  inlets  or  gutters,  shall  be  removed  within  three  hours  from 
the  time  such  heaps  are  made,  in  carts  tightly  built  in  such  a  man- 
ner that  the  contents  can  be  removed  without  spilling  or  leaking, 
and  the  place  where  they  had  been  collected  shall  be  swept  clean. 

All  gutters  kept  wet  by  the  flow  of  filthy  water  or  sewage  shall 
be  thoroughly  scraped,  brushed,  and  flushed  at  least  twice  a  week 
from  May  1st  to  November  1st,  and  for  this  work  each  contractor 
will  be  required  to  keep  at  least  100  feet  of  hose  in  each  district, 
and  brushes  or  brooms  especially  made  for  work  of  this  kind  shall 
be  used  in  cleaning  the  gutters. 

All  solid  matter  must  be  removed  from  the  gutters  and  inlets 
before  they  are  flushed. 

All  street  crossings,  inlets,  gutters  approaching  the  same,  and 
all  gutters  necessary  to  drain  crossings  within  100  feet  of  inlets, 
and  streets  in  front  of  fire-plugs,  for  a  radius  of  5  feet,  must  be 
kept  clean  of  dirt,  mud,  ice,  and  snow. 

1028.  Instructions  to  Bidders.  —  Proposals  for  [insert  descrip- 
tion and  location  of  the  work].  In  pursuance  of  the  follow- 

ing ordinance  [insert  ordinance]. 

Sealed  proposals  for  the  above  work,  indorsed  with  the  above 
title,  also  with  the  names  of  the  person  or  persons  making  the  same 
and  the  date  of  presentation,  will  be  received  at  the  office  of 

until        o'clock     .M.,  day   of  ,  189    ,  at 

which  place  and  hour  the  bids  will  be  publicly  opened  by 
and  read,  and  the  award  of  the  contract  will  be  made  to  the  lowest 
responsible   bidder  with  adequate   security   as   soon   thereafter  as 
practicable.     The  person  or  persons  to  whom  the  contract  may  be 
awarded  will  be  required  to  attend  at  the  office  of  with  the 

sureties  offered  by  him  or  them,  and  execute  the  contract  within 


HIGHWAY   CONSTRUCTION 


five  days  from  the  date  of  the  service  of  a  notice  to  the  effect  that 
the  contract  has  been  so  awarded,  and  that  the  adequacy  and  suffi- 
ciency of  the  security  offered  has  been  approved  by  the  ; 

in  case  of  failure  or  neglect  so  to  do,  he  or  they  will  be  con- 
sidered as  having  abandoned  it,  and  as  in  default  to  the  ; 

and  thereupon  the  work  will  be  readvertised  and  relet,  and  so  on 
until  the  contract  be  accepted  and  executed.  The  work  is  to  be 
commenced  at  such  time  as  the  engineer  may  designate. 

The  price  must  be  written  in  the  bid,  and  also  stated  in  figures, 
and  all  proposals  will  be  considered  as  informal  which  do  not  con- 
tain bids  for  all  the  items  for  which  prices  are  herein  called  for,  or 
which  contain  prices  for  items  not  called  for,  or  which  contain 
erasures,  alterations,  or  other  irregularities. 

Permission  will  not  be  given  for  the  withdrawal  of  any  bid  or 
estimate,  and  the  right  is  expressly  reserved  by  the  to  re- 

ject all  bids  if  it  shall  be  deemed  for  the  public  interest  so  to  do. 
No  bid  will  be  accepted  from  or  contract  awarded  to  any  person 
who  is  in  arrears  to  the  upon  debt  or  contract,  or  who  is  a 

defaulter,  as  surety  or  otherwise,  upon  any  obligations  to  the 

Bidders  are  required  to  state  in  their  estimates,  under  oath,  their 
names  and  places  of  residence,  the  names  of  all  persons  interested 
with  them  therein,  and  if  no  other  person  be  so  interested,  they 
shall  distinctly  state  the  fact  ;  also  that  it  is  made  without  any  con- 
nection with  any  other  person  making  a  bid  or  estimate  for  the  same 
work,  and  that  it  is  in  all  respects  fair  and  without  collusion  or  fraud  ; 
and  also  that  no  member  of  or  other  officer  of  the 

is  directly  or  indirectly  interested  therein,  or  in  the  sup- 
plies or  work  to  which  it  relates,  or  in  any  portion  of  the  profits- 
thereof.  Where  more  than  one  person  is  interested,  it  is  requisite- 
that  the  verification  be  made  and  subscribed  by  all  the  parties  inter- 
ested. 

Each  estimate  shall  be  accompanied  by  the  consent,  in  writing, 
of  two  householders  or  freeholders  in  the  ,  with  their  re- 

spective places  of  residence,  tt>  the  effect  that  if  the  contract  be 
awarded  to  the  person  making  the  estimate,  they  will,  upon  its  being 
so  awarded,  become  bound  as  his  sureties  for  its  faithful  perform- 
ance; and  that  if  he  shall  omit  or  refuse  to  execute  the  same,  they 
will  pay  to  the  any  difference  between  the  sum  to  which 

he  T&ould  be  entitled  upon  its  completion,  and  that  which  the  said 


SPECIFICATIONS   AND    CONTRACTS.  G9L 

may  be  obliged  to  pay  to  the  person  to  whom  the  con- 
tract shall  be  awarded  at  any  subsequent  letting;  the  amount  in 
each  case  to  be  calculated  upon  the  estimated  amount  of  the  work 
by  which  the  bids  are  tested.  The  consent  above  mentioned  shall 
be  accompanied  by  the  oath  or  affirmation,  in  writing,  of  each  of 
the  persons  signing  the  same,  that  he  is  a  householder  or  freeholder 
in  the  and  is  worth  the  amount  of  the  security  required 

for  the  completion  of  the  contract  and  stated  in  the  proposals,  over 
and  above  all  his  debts  of  every  nature  and  over  and  above  his  lia- 
bilities as  bail,  surety,  and  otherwise,  and  that  he  has  offered  himself 
as  surety  in  good  faith  and  with  an  intention  to  execute  the  bond 
required  by  law.  The  adequacy  and  sufficiency  of  the  security 
offered  will  be  determined  by  the  of  the 

In  case  a  proposal  is  submitted  by  or  in  behalf  of  any  corpora- 
tion it  must  be  signed  in  the  name  of  such  corporation  by  some 
duly  authorized  officer  or  agent  thereof,  who  shall  also  subscribe 
his  own  name  and  office.  If  practicable,  the  seal  of  the  corporation 
should  also  be  affixed. 

The  successful  bidder  will  be  strictly  held  to  the  time  bid  for 
completion  of  the  work,  and  to  the  conditions  of  the  specifications. 

The  engineer's  estimate  of  the  nature  and  extent  of  the  work  to 
be  done  and  materials  to  be  furnished  is  as  follows :  [Insert  esti- 
mate.] 

As  the  above  quantities,  though  stated  with  as  much  accuracy 
as  is  possible  in  advance,  are  approximate  only,  bidders  are  required 
to  submit  their  estimate  upon  the  following  express  conditions, 
which  shall  apply  to  and  become  part  of  every  estimate  received : 

1.  The  items  and  quantities  stated  in  the  above  schedule  are 
merely  approximate  and  may  be  altered  in  part  or  wholly  changed 
during  the  progress  of  the  work.     They  are  intended  only  to  indi- 
cate the  general  character  of  the  work  and  shall  not  be  made  a 
basis  of  any  claim  for  extra  compensation  of  profits  in  case  the 
quantities  of  the  final  estimate  shall  vary  from  them,  nor  be  regarded 
as  having  any  relation  or  bearing  whatever  upon  the  quantities  of 
the  final  estimate. 

2.  Bidders  must  satisfy  themselves  by  personal  examination  of 
the  site  of  the  proposed  work  as  to  the  difficulties  to  be  encountered 
and  such  other  matters  which  can  in  any  way  influence  their  esti- 
mates, and  no  information  derived  from  the  drawings  or  specifica- 


692  HIGHWAY   CONSTRUCTION. 

tions  or  from  the  engineer  or  any  of  his  assistants  will  relieve  the 
contractor  from  any  risks  or  from  fulfilling  the  terms  of  the  specifi- 
cations and  contract. 

3.  The  contractor  will  be  required  to  complete  the  entire  work 
to  the  satisfaction  of  the  and  in  substantial  accordance 

with  the  specifications. 

Ko  estimate  will  be  received  or  considered  unless  accompanied 
by  either  a  certified  check  upon  one  of  the  National  or  State  banks 
of  the  drawn  to  the  order  of  the  ,  or  money 

to  the  amount  of  five  per  centum  of  the  amount  of  the  security  re- 
quired for  the  faithful  performance  of  the  contract.  Such  check  or 
money  must  not  be  inclosed  in  the  sealed  envelope  containing  the  es- 
timate, but  must  be  handed  to  the  officer  or  clerk  of  the  department 
who  has  charge  of  the  estimate  box,  and  no  estimate  can  be  de- 
posited in  said  box  until  such  check  or  money  has  been  examined 
by  said  officer  or  clerk  and  found  to  be  correct.  All  such  deposits, 
except  that  of  the  successful  bidder,  will  be  returned  to  the  persons 
making  the  same  within  three  days  after  the  contract  is  awarded. 
If  the  successful  bidder  shall  refuse  or  neglect,  within  five  days  after 
notice  that  the  contract  has  been  awarded  to  him,  to  execute  the 
same,  the  amount  of  the  deposit  made  by  him  shall  be  forfeited  to 
and  retained  by  the  as  liquidated  damages  for  such 

neglect  or  refusal;  but  if  he  shall  execute  the  contract  within  the 
time  aforesaid,  the  amount  of  his  deposit  will  be  returned  to 
him. 

Bidders  are  particularly  cautioned  that  in  no  case  will  they  be 
permitted  to  use  materials  either  in  quantity  or  quality  different 
from  those  described  in  the  specifications.  [And  also,  that  a  pro- 
vision in  the  specifications  and  contract  requires  the  maintenance 
of  the  pavement  in  good  condition  for  the  period  of  from 

the  final  completion  and  acceptance  thereof.] 

The  amount  of  security  is  thousand  dollars  for  the 

faithful  performance  of  the  contract,  and  also  for  the  indemnifica- 
tion of  the  for  infringement  of  patents  the  amount  is 
thousand  dollars.  The  contractor  must  notify  the  en- 
gineer in  writing  hours  before  commencing  the  work. 
The  plans  can  be  seen  and  blank  forms  of  proposals  and  further 
information  can  be  obtained  on  application  at  the  office  of 


SPECIFICATIONS   AND    CONTRACTS.  693 

1029.  Form  of  Proposal. 

NO.  BID   OB   ESTIMATE. 

For  [insert  description  of  work]  ,  made  by  ,  resid- 

ing at  ,  and  residing  at  ,  and  resid- 

ing at  ,and  residing  at  ,  composing  the  firm 

of 

1.  declare    that  the   only    person  in- 
terested in  this  proposal;  and  no  other  person                other  than 
herein  above  named  ha     any  interest  in  this  proposal,  or  in  the 
contract  proposed  to  be  taken. 

2.  further  declare  that  this  proposal  is  made  without 
connection   with    any   other    person   or  persons    making  a    pro- 
posal for  the  same  purpose,  and  is  in  all  respects  fair,  and  without 
collusion  or  fraud. 

3.  further  declares  that  no  member  of  the  or 
other  officer  is  directly  or  indirectly  interested  in  this  proposal,  or 
in  the  supplies  or  work  to  which  it  relates,  or  in  any  portion  of  the 
profits  thereof. 

4.  further   declares    that  the   names   of  the  persons 
affixed  to  the  consent  hereto  annexed  were  written  by  said  persons 
respectively,  and  that  said  persons  are  householders  or  freeholders 
in  the 

5.  have  examined  the  proposals  for  estimates  for  the 
above   work,   dated  the  day  of  ,  189     ,   and  pub- 
lished in  the                ,   and  the  form  of  contract   for   the    work 
(including  the  plans  and  specifications  for  the  work),  and  have 
also  visited  and  examined  the  site  and  location  and  made  the  in- 
vestigations   recommended   in    the   instructions   to    bidders,   and 

will  contract  to  furnish  the  material  and  perform  and 
complete  the  work  mentioned  in  said  proposals  for  estimates  and 
approved  form  of  contract  on  the  following  terms,  viz. :  For  clear- 
ing, grubbing  and  close  cutting,  per  acre,  the  sum  of  ,     For 
earth  excavations  for  all  classes,  per  cubic  yard,  the  sum  of 
For  loose  rock  excavation,  per  cubic  yard,  the  sum  of 
For    solid  rock  excavation,  per  cubic  yard,  the   sum   of 
For   12-inch  culvert   pipe,  per  linear  foot,  the  sum  of 
For   24-inch   culvert  pipe,   per  linear  foot,  the   sum  of 
For  concrete,  per  cubic  yard,  the  sum  of            .     For  each  receiving 
basin,  complete,  with  iron  head  and                grating,  the  sum  of 


694  HIGHWAY    CONSTRUCTION. 

For  brick  masonry,  per  cubic  yard,  the  sum  of 
For  yellow-pine   timber,  including    fastenings,  per   1000 
feet-board  measure,  the  sum  of  For  spruce  and  other  plank, 

including  fastenings,  per   1000  feet  board  measure,  the  sum  of 
.    For  riprap,  per  cubic  yard,  the  sum  of  .    For  dry 

stone  masonry,  per  cubic  yard,  the  sum  of 

The  above  prices  include  the  furnishing  of  all  the  materials, 
tools,  plant,  and  labor,  and  every  risk  and  contingency  necessary 
for  the  completion  of  the  work  in  accordance  and  with  specifica- 
tions and  plans. 

Time  within  which  will  complete  the  whole  work  ac- 

cording to  specifications  days. 


CITY  OF  ,  COUNTY  OF  ,  ss.  : 


being  duly  sworn,  say,  each  for  himself,  that  the  several  matters 
stated  in  the  above  estimate  are  in  all  respects  true. 

Subscribed  and  sworn  to  this  day  of  ,  A.D.  189  , 

before  me, 


Commissioner  of  Deeds. 

1030.  Form  of  Agreement  (to  be  executed  in  triplicate). 

This  agreement  made  and  entered  into  this  day  of  , 

one  thousand  eight  hundred  and  ,  by  and  between  the  [in- 

sert name  of  city,  town,  or  county]  of  ,  hereinafter  called  the 

party  of  the  first  part,  and  [name  of  contractor],  of  the 
[insert  place  of  residence],  hereinafter  called  the  party  of  the  second 
part, 

Witnesseth :  That  the  said  party  of  the  second  part  has  agreed, 
and  by  these  presents  does  for  himself,  his  heirs,  executors,  admin- 
istrators, and  assigns,  covenant,  promise,  and  agree  with  the  said 
parties  of  the  first  part,  for  the  considerations  hereinafter  mentioned 


SPECIFICATIONS   AND    CONTRACTS.  695 

and  contained,  and  under  the  penalty  expressed  in  a  bond  bearing 
even  date  with  these  presents,  and  hereunto  annexed,  that  he,  the 
said  party  of  the  second  part,  his  heirs,  executors,  administrators,  or 
assigns,  shall  and  will  furnish  and  provide,  at  his  own  or  their  own 
cost  and  expense,  all  the  necessary  materials,  appliances,  tools,  plant, 
and  labor  which  are  or  may  be  necessary  for  the  proper  and  sub 
stantial  construction  and  completion  of  the  [insert  description  of 
work],  in  accordance  with  the  general  plans  on  file  in  the  office  of 
the  said  party  of  the  first  part,  and  in  strict  conformity  in  every 
part  and  particular  with  the  following  specifications,  and  in  accord- 
ance with  such  detail  plans  and  instructions  relating  thereto  as  may 
from  time  to  time  be  given  by  the  chief  engineer  or  his  duly 
appointed  assistants;  and  further  agrees  that  the  said  parties  of  the 
first  part  shall  be,  and  are  hereby,  authorized  by  their  chief  engineer, 
or  such  other  person  or  persons,  or  in  such  other  manner,  as  they 
may  deem  proper,  to  inspect  the  material  to  be  furnished  and  the 
work  to  be  done  under  this  agreement,  and  to  see  that  the  same 
correspond  with  the  specifications  and  conditions  hereinafter  set 
forth. 

The  party  of  the  second  part  admits  and  agrees  that  the  amounts 
and  quantities  of  materials  to  be  furnished  and  work  to  be  done,  as 
stated  in  the  proposals  for  estimates  for  the  said  work,  are  approxi- 
mate only;  that  he  is  satisfied  with  the  foregoing  estimate  in  de- 
termining the  price  according  to  which  he  agrees  to  do  the  work 
required  by  this  contract  in  accordance  therewith,  and  that  he  shall 
not  and  will  not  dispute  or  complain  of  such  statement,  nor  assert 
that  there  was  any  misunderstanding  in  regard  to  the  nature  or 
amount  of  the  materials  to  be  furnished  or  work  to  be  done;  and 
he  covenants  and  agrees  that  he  will  complete  the  entire  work  to 
the  satisfaction  of  the  and  in  substantial  accordance  with 

said  specifications  and  the  plan  therein  mentioned,  and  that  he  will 
not  ask,  demand,  sue  for,  or  recover  for  the  entire  work  any  extra 
compensation  beyond  the  amount  payable  for  the  several  classes  of 
work  in  this  contract  enumerated,  which  shall  be  actually  performed, 
at  the  price  therefor  herein  agreed  upon  and  fixed. 

The  parties  hereto  also  declare  that  this  contract  is  made  with 
reference  to  the  proposals  for  estimates  for  the  above-described 
work,  hereto  annexed,  and  the  estimate  of  the  contractor  now  on  file 


696  HIGHWAY   CONSTRUCTION. 

in  the  ,  which  are  to  be  taken  as  part  and  parcel  of  these 

presents  [here  insert  specifications  and  general  stipulations]. 

Commencement. — The  said  party  of  the  second  part  hereby 
further  agrees  to  commence  the  work  comprised  under  this  agree- 
ment on  such  day  and  at  such  place  or  places  as  the  engineer  may 
designate.  Failure  to  so  commence  will  be  authority  for  the  party 
of  the  first  part  to  declare  this  agreement  forfeited,  and  the  said 
party  of  the  first  part  may  proceed  with  the  execution  of  the  work 
in  such  manner  as  they  may  deem  proper. 

Time  of  Completion. — The  party  of  the  second  part  agrees  to 
prosecute  the  work  in  such  manner  as  to  complete  the  same  in 
accordance  with  this  agreement  on  or  before  the  expiration  of  two- 
hundred  (200)  days  after  the  date  of  commencement,  and  it  is. 
further  agreed  that  in  the  computation  of  said  time,  the  length  of 
time  (expressed  in  days  and  parts  of  a  day)  during  which  the  work 
or  any  part  thereof  has  been  delayed  in  consequence  of  the  condi- 
tion of  the  weather,  or  by  any  difficult  circumstances  so  unusual 
that  they  could  not  be  foreseen  previous  to,  or  avoided  during,  the 
construction  of  the  work,  or  by  any  act  or  omission  of  the  parties 
of  the  first  part  (all  of  which  shall  be  determined  by  the  chief  en- 
gineer, who  shall  certify  to  the  same  in  writing),  and  also  Sundays 
and  holidays  on  which  no  work  is  done,  and  days  on  which  the 
prosecution  of  the  work  is  suspended,  by  order  of  the  party  of  the 
first  part,  shall  be  excluded. 

But  if  the  construction  of  said  work  should  require  material  or 
work  in  greater  or  lesser  quantities  or  amounts  than  those  men- 
tioned and  set  forth  in  the  engineer's  estimate,  then  the  said  time 
shall  be  increased  or  diminished  as  much  as  the  said  engineer,  by 
a  certificate  in  writing,  shall  deem  just  and  reasonaole,  and  fairly 
proportioned  to  the  amount  of  said  increase  or  diminution. 

But  neither  an  extension  of  time  for  any  reason  beyond  the  date 
fixed  herein  for  the  completion  of  the  work,  nor  the  doing  and  ac- 
ceptance of  any  part  of  the  work  called  for  by  this  agreement, 
subsequent  to  the  said  date,  shall  be  deemed  to  be  a  waiver  by  the 
said  party  of  the  first  part  of  the  right  to  abrogate  this  contract  for 
abandonment  or  delay  in  the  manner  provided  for  in  Article  80  of 
this  agreement. 

Damages  for  Non-completion. — And  the  said  party  of  the  second 
part  hereby  further  agrees,  that  the  said  parties  of  the  first  part 


SPECIFICATIONS   AND    CONTRACTS.  G97 

shall  be  and  are  hereby  authorized  to  deduct  and  retain  out  of  the 
moneys  which  may  be  due  or  become  due  to  the  said  party  of  the 
second  part  under  this  agreement,  as  damages  for  the  non-comple- 
tion of  the  work  aforesaid  within  the  time  hereinbefore  stipulated 
for  its  completion,  the  sum  of  dollars  for  each  and  every  day 

which  may  exceed  the  said  stipulated  time  for  its  completion;  which 
said  sum  of  dollars  per  day  is  hereby,  in  view  of  the  difficulty 

of  estimating  such  damages  agreed  upon,  fixed  and  determined  by 
the  parties  hereto  as  the  liquidated  damages  that  the  parties  of  the 
first  part  will  suffer  by  reason  of  such  default,  and  not  by  way  of 
penalty. 

Improper  Prosecution  of  Work. — The  said  party  of  the  second 
part  further  agrees  that  if  at  any  time  it  should  appear  to  the  en- 
gineer that  the  works  are  being  delayed,  or  are  not  being  prosecuted 
with  due  diligence,  or  with  such  speed  as  would  be  necessary  for 
their  completion  within  the  time  specified,  or  that  the  works  are 
being  prosecuted  in  an  improper  or  unworkmanlike  manner,  the  said 
engineer  shall  notify  the  contractor  in  writing,  specifying  the  causes, 
of  complaint,  and  upon  the  party  of  the  second  part  failing  to 
rectify  such  matters  within  seven  days  after  the  receipt  of  said 
aotice,  the  engineer  shall  notify  the  party  of  the  first  part  of  such 
failure;  and  it  is  further  agreed,  that  in  the  event  of  such  failure 
^he  party  of  the  first  part  may,  without  further  notice,  suspend  the 
7nontractor  from  all  work  under  this  agreement;  and  it  is  further 
Agreed,  that  the  said  party  of  the  second  part  shall  immediately 
respect  said  suspension,  and  shall  stop  work,  and  cease  to  have  any 
rights  to  possession  of  the  ground ;  and  the  said  party  of  the  first 
part  shall  thereupon  have  the  power  to  carry  on  and  complete  the 
work  herein  described,  by  contract  or  otherwise,  employing  such 
plant,  tools,  and  materials  as  may  be  on  the  ground,  and  procuring 
such  others  as  may  be  wanting,  for  the  proper  completion  of  the 
work,  and  to  charge  the  expense  of  such  labor  and  materials  to  the 
aforesaid  party  of  the  second  part,  and  the  expense  so  charged 
shall  be  deducted  and  paid  out  of  such  moneys  as  may  be  then  due, 
or  may  at  any  time  thereafter  become  due,  to  the  said  party  of  the 
second  part  under  or  by  virtue  of  this  agreement,  or  any  part 
thereof;  any  excess  of  cost  over  and  above  the  amount  accruing  as 
above  stated  shall  be  charged  against  the  party  of  the  second  part 
ana  his  sureties,  who  will  each  and  severally  be  held  liable  there- 


(598  HIGHWAY    CONSTRUCTION". 

for;  and  in  case  the  cost  of  completion  shall  be  less  than  the  sum 
which  would  have  been  payable  under  this  contract  if  the  same  had 
been  completed  by  the  party  of  the  second  part,  he  shall  be  entitled 
to  receive  the  difference. 

Engineer's  Returns. — The  said  party  of  the  second  part  further 
agrees  that  the  return  of  the  engineer  shall  be  the  account  by 
which  the  amount  of  material  furnished  and  work  done  in  terms 
of  this  contract  shall  be  computed ;  provided,  however,  that  nothing 
herein  contained  be  construed  to  affect  the  right  of  the  party  of  the 
first  part  to  reject  and  contest  any  return  or  certificate  of  the  en- 
gineer or  inspectors  having  charge  of  the  work,  should  such  return 
or  certificate  be  in  their  opinion  not  in  accordance  with  the  facts 
of  the  case  or  the  requirements  of  this  agreement,  or  otherwise 
Improperly  given. 

Damage  to  Property. — And  it  is  hereby  further  agreed,  that 
in  case  any  damage  or  injury  shall  or  may  result  to  buildings, 
water-pipes,  hydrants,  gate-boxes,  sewer-basins,  man-holes,  sewers, 
or  other  works  through  or  by  reason  of  any  negligence,  careless- 
ness, or  want  of  skill  on  part  of  said  party  of  the  second  part,  the 
said  party  of  the  second  part  shall  restore  the  same  to  their  former 
good  condition;  failing  to  do  so,  said  party  of  the  second  part 
shall  pay  such  amount  as  shall  or  may  be  sufficient  to  cover  the 
expense  and  damage  occasioned  by  such  negligence,  carelessness, 
or  unskilfulness. 

Gas-pipes.— And  the  said  party  of  the  second  part  further 
agrees  to  do  everything  necessary  to  support  and  sustain  the  gas- 
pipes  laid  in  or  across  said  streets,  which  may  be  liable  to  any  in- 
jury from  digging  the  trenches  for  the  work  hereinbefore  men- 
tioned, and  to  have  a  sufficient  quantity  of  timber  and  plank  con  - 
stantly  on  the  ground,  and  to  use  the  same  as  required  for  bracing 
and  sheet-piling  the  sides  of  the  excavation. 

Notice  to  Gas  Companies. — And  the  said  party  of  the  second 
part  further  agrees  to  give  notice  in  writing,  at  least  twenty-four 
hours  before  breaking  ground  for  the  purpose  of  constructing  the 
work  hereinbefore  mentioned,  to  such  and  all  such  gas  companies 
as  have,  or  may  during  the  progress  of  the  work  have,  any  gas-pipes 
Which  may  be  affected  by  such  excavations  as  may  become 
necessary. 

And  it  is  further  agreed,  that  the  said  party  of  the  second  part 


SPECIFICATIONS   A XI)   CONTRACTS.  099 

shall  not  cause  any  hindrance  to  or  interfere  with  such  gas  com- 
pany or  companies  in  protecting  their  pipes,  nor  in  removing  or 
•otherwise  protecting  and  replacing  the  main  and  service  pipes, 
lamp-posts  and  lamps,  where  necessary;  but  that  the  said  party  of 
the  second  part  will  suffer  the  said  company  or  companies  to  take 
all  such  measures  as  may  become  necessary  for  the  purpose  afore-- 
said. 

Penalty  of  Damage  to  Gax-pipes. — And  it  is  hereby  further 
agreed,  that  in  case  any  damage  or  injury  shall  or  may  result  to  the 
said  pipes,  lamp-posts,  lamps,  or  other  works  of  any  gas  company, 
through  or  by  reason  of  any  negligence,  carelessness,  or  want  of 
skill  on  the  part  of  the  said  party  of  the  second  part,  his  agents  or 
servants,  the  said  party  of  the  second  part  shall  become  'liable  to 
pay  such  amount  as  shall  or  may  be  sufficient  to  cover  the  expense 
and  damage  occasioned  by  such  negligence,  carelessness,  or  unskil- 
fulness;  and  such  amount  shall  be  charged  against  the  said  party 
of  the  second  part,  and  may  be  deducted  from  any  sum  or  sums 
due  or  to  become  due  or  payable  to  said  party  of  the  second  part  on 
account  of  this  contract. 

Water-pipes. — The  party  of  the  second  part  hereby  further 
agrees  to  sustain  in  their  places,  without  injury,  all  the  main  and 
service  water-pipes  which  may  be  affected  in  any  manner  by  the 
work  under  this  agreement,  including  any  such  protective  meas- 
ures as  may  be  required  in  cold  weather  to  prevent  them  from 
freezing;  or  failing  to  do  so,  the  said  shall  be  and  he  is 

hereby  authorized  to  replace  and  recalk  and  repair  the  same  im- 
mediately in  each  block,  as  the  work  progresses,  and  the  cost  there- 
of shall  be  charged  to  the  said  party  of  the  second  part,  and  the 
•cost  so  charged  to  the  said  party  of  the  second  part  shall  be  re- 
tained and  deducted,  and  the  parties  of  the  first  part  are  hereby 
authorized  to  retain  and  deduct  said  cost  out  of  the  moneys  which 
may  be  due  or  become  due  to  the  said  party  of  the  second  part 
under  this  agreement. 

Transfer  of  Contract. — The  party  of  the  second  part  further 
agrees  not  to  transfer  or  sublet  any  part  of  the  work  referred  to  in 
this  agreement,  without  the  previous  written  consent  of  the  en- 
gineer; any  such  transfer  or  subletting  without  said  consent  will 
be  null  and  void,  and  will  be  sufficient  cause  for  the  annulment  of 


7()0  HIGHWAY    CONSTRUCTION. 

the  contract;  nor  shall  any  of  the  moneys  payable  under  this  con- 
tract be  assigned  by  power  of  attorney  or  otherwise. 

Loss  or  Damage. — And  it  is  further  agreed  that  all  loss  or 
damage  arising  out  of  the  nature  of  the  work  to  be  done,  or  from 
any  unforeseen  or  unusual  obstructions  or  difficulties  which  may 
be  encountered  in  the  prosecution  of  the  same,  or  from  the  action 
of  the  elements,  or  from  injury  to  persons  or  property  of  another, 
resulting  from  negligence  in  the  performance  and  guarding  of  the 
same,  which  must  be  protected  when  necessary  with  barriers,  and 
at  night  with  red  lights,  or  from  any  improper  materials  used  in 
prosecution  or  by  or  on  account  of  any  act  or  omission  of  his  own, 
or  his  agents,  will  be  sustained  by  the  contractor,  and  he  shall  save 
harmless  £he  party  of  the  first  part  from  any  and  all  liabilities  and 
claims  for  such/ and  the  said  party  of  the  first  part  shall  have  the 
right  to  retain  any  moneys  that  may  be  due  or  become  due,  until 
evidence  has  been  furnished  that  all  such  suits  or  claims  for 
damages  as  aforesaid  have  been  satisfactorily  settled. 

Public  Protection. — It  is  further  agreed  that  the  contractor 
will  enclose  every  opening  he  may  make  in  the  public  highway 
with  sufficient  barriers,  and  must  maintain  red  lights  at  the  same 
at  night,  and  must  take  all  necessary  precautions  to  guard  effectu- 
ally against  accidents  to  persons,  horses,  vehicles,  or  property  of 
any  kind,  and  all  work  shall  be  done  in .  such  manner  and  at  such 
times  as  to  interfere  as  little  as  possible  with  public  travel  and 
convenience;  and  the  contractor  shall  conduct  his  work  for  this 
object  as  the  engineer  may  from  time  to  time  direct. 

Work  not  Provided  for  in  Contract. — The  said  party  of  the 
second  part  further  agrees,  that  if,  before  the  completion  of  the 
work  contemplated  herein,  it  shall  become  necessary  to  do  any 
other  or  further  work  on  or  about  this  regulating,  etc.,  than  is  pro- 
vided for  in  this  contract,  or  to  construct  any  sewer  or  sewers  or 
appurtenances  thereof,  on  the  line  of  this  work,  the  said  party  of 
the  second  part  will  not  in  any  way  interfere  with  or  molest  such 
other  person  or  persons  as  the  may  employ  to  do  such  work, 

and  will  suspend  each  part  of  the  work  herein  specified,  or  will 
carry  on  the  same  in  such  manner  as  may  be  ordered  by  the  said 
,  to  afford  all  reasonable  facilities  for  doing  such  work, 
and  no  other  damage  or  claim  by  the  said  party  of  the  second  part 
hereof  shall  be  allowed  except  such  extension  of  the  time  specified 


SPECIFICATIONS   AND   CONTRACTS.  701 

in  this  contract  for  the  performance  thereof  as  the  may 

deem  reasonable. 

Security  to  be  retained  for  Repairs. — And  the  said  party  of 
the  second  part  hereby  further  agrees  that  the  said  parties  of  the 
first  part  shall  be  and  are  hereby  authorized  to  retain,  out  of  the 
moneys  payable  to  him  under  this  agreement,  the  certain  sum  of 
twenty-five  cents  per  linear  foot  o'f  the  work  done  under  this  agree- 
ment, and  to  expend  the  same,  in  the  manner  provided  for,  in  mak- 
ing such  repairs  to  the  work  done  under  this  agreement  as  the  said 
may  deem  necessary,  except  curbing  and  flagging,  which 
will  be  finally  accepted  upon  the  completion  of  the  work.  And  it 
is  further  agreed  that  if,  at  any  time  during  the  period  of  six 
months  from  the  date  of  the  acceptance  by  said  of  the 

work  under  this  agreement,  the  said  work  or  any  part  thereof  (ex- 
cepting only  such  part  or  parts  of  the  work  as  after  the  completion 
thereof  may  have  been  disturbed  in  the  construction  or  repairs  of 
sewers  or  drains,  or  in  laying  or  repairing  gas  or  water  main  or 
service  pipes,  or  railroad-pier  foundations)  shall  in  the  opinion  of 
the  said  require  repairs,  the  said  shall  notify  the 

said  party  of  the  second  part  to  make  the  repairs  so  required,  the 
said  party  of  the  second  part  shall  immediately  commence  and 
complete  the  same  to  the  satisfaction  of  said  ;  and  in 

case  of  failure  or  neglect,  on  his  part,  to  do  so  within  forty-eight 
hours  from  the  date  of  the  service  of  the  aforesaid  notice,  then  the 
said  shall  have  the  right  to  purchase  such  materials  as  fee 

shall  deem  necessary,  and  to  employ  such  person  or  persons  as  he 
may  deem  proper,  and  to  undertake  and  complete  the  said  repairs, 
and  to  pay  the  expense  thereof  out  of  the  said  certain  sum  retained 
for  that  purpose  by  the  said  parties  of  the  first  part,  as  before  men- 
tioned. And  the  parties  of  the  first  part  hereby  agree,  upon  the 
expiration  of  the  said  period  of  six  months,  provided  that  the  said 
work  at  that  time  be  in  good  order,  or  as  soon  thereafter  as  the  said 
work  shall  have  been  put  in  good  order  to  the  satisfaction  of  the 
said  ,  to  pay  to  the  said  party  of  the  second  part  the  whole 

of  the  sum  last  aforesaid  or  such  part  thereof  as  may  remain  after 
the  expense  of  making  such  repairs,  in  the  manner  aforesaid,  shall 
have  been  paid  therefrom.  And  it  is  hereby  further  agreed,  between5 
the  parties  hereto,  that  if  the  termination  of  the  said  period  of  six 
months  after  the  completion  and  acceptance  of  the  work  done 


702  HIGHWAY    CONSTRUCTION. 

under  this  agreement  shall  fall  within  the  months  of  December, 
January,  February,  and  March,  then  in  that  case  the  said  months 
of  December,  January,  February,  and  March,  or  such  part  thereof 
as  the  may  determine,  shall  not  be  included  in  the  compu- 

tation of  the  said  period  of  six  months. 

Prices. — And  the  party  of  the  second  part  hereby  further  agrees 
to  receive  the  prices  set  forth  in  the  following  schedule  as  full 
compensation  for  furnishing  all  materials  and  labor,  and  the  doing 
of  all  work,  including  all  loss  or  damage  arising  out  of  the  nature  of 
the  work,  or  from  the  action  of  the  elements,  or  from  any  unforeseen 
obstructions  or  difficulties,  which  may  be  encountered  in  the  prose- 
cution of  the  same ;  also  all  expenses  incurred  by  or  in  consequence 
of  the  suspension  or  discontinuance  of  said  work  which  may  be 
required  in  building  and  constructing,  and  in  all  respects  complet- 
ing the  aforesaid  [insert  description  of  work],  including  all  appur- 
tenances and  accessories,  to  the  satisfaction  of  the  engineer  and  the 
hereinbefore  mentioned  authorities,  and  in  the  manner  and  under 
the  conditions  hereinbefore  specified,  to  wit :  [insert  schedule  of 
prices]. 

Manner  of  Payment. — And  the  said  party  of  the  second  part 
further  agrees  that  he  shall  not  be  entitled  to  demand  or  receive 
payment  for  any  of  the  aforesaid  work  or  material  until  the  same 
shall  be  fully  completed  in  the  manner  set  forth  in  this  agreement, 
and  such  completion  duly  certified  by  the  chief  engineer,  and  until 
each  and  every  one  of  the  stipulations  hereinbefore  mentioned  are 
complied  with. 

Whereupon  the  parties  of  the  first  part  will  pay,  and  hereby 
bind  themselves  and  their  successors  to  pay,  to  the  said  party  of  the 
second  part,  on  account,  ninety  (90)  per  cent  of  the  monthly  esti- 
mate of  the  whole  amount  of  money  accruing  to  the  said  party  of 
the  second  part,  and  the  reserved  ten  (10)  per  cent  upon  the  formal 
acceptance  of  the  work  by  the  party  of  the  first  part. 

In    witness    whereof,    the  ha      hereunto    set 

hand    and  seal    on  behalf  of  the  said  parties  of  the  first  part,  and 
the  said  party  of  the  second  part  hath  also  hereunto  set 
hand     and  seal  ,  the  day  and  year  first  above  written;  and  said 
commissioner  and  party  hereto  of  the  second  part  hath  executed 
this  agreement  in  triplicate,  one  part  of  which  is  to  remain  with 


SPECIFICATIONS    AND    CONTRACTS.  703 

the  said  ,  one  other  to  be  filed  with  the  ,  and  the 

third  to  be  delivered  to  the  said  party  hereto  of  the  second  part. 

Signed  and  sealed  in  presence  of 


Contractor. 

STATE  OF  ,  CITY  OF  ,  COUNTY  OF  ,  ss.  : 

On  this  day  of  ,  189  ,  before  me  personally  came 

to  me  known,  and  known  to  me  to  be  the  ,  the  person  de- 

scribed in  and  who  executed  the  foregoing  instrument,  and  he 
acknowledged  to  me  that  he  executed  the  same  as  such  , 

for  the  purposes  therein  mentioned. 


Commissioner  of  Deeds, 
County- 

STATE  OF  ,  CITY  OF  ,  COUNTY  OF  ,  ss.  : 

On  this  day  of  189  ,  before  me  personally  came 

to  me  known,  and  known  to  me  to  be  the  person  described  in  and 
who  executed  the  foregoing  instrument,  and  he  acknowledged 
to  me  that  he  executed  the  same  for  the  purposes  therein  men- 
tioned. 


Commissioner  of  Deeds, 
County. 

1031.  Form  of  Bond. 

Know  all  men  by  these  presents,  that  we, 

of  the  ,  are  held  and  firmly  bound  unto  the  of  the 

in  the  sum  of  thousand  dollars  lawful  money  of 

the  United  States  of  America,  to  be  paid  to  the  said  ,  or 

to  their  certain  attorney,  successors,  or  assigns;  for  which  pay- 
ment, well  and  truly  to  be  made,  we  bind  ourselves,  and  our  several 
and  respective  heirs,  executors,  and  administrators,  jointly  and 
severally,  firmly  by  these  presents.  " 


704  HIGHWAY   CONSTRUCTION. 

Sealed  with  our  seals.     Dated  this  day  of  ,  ono 

thousand  eight  hundred  and 
Whereas,  the  above  bounden 

by  an  instrument  in  writing  under  hand        and  seal        , 

bearing  even  date  with  these  presents,  ha  contracted  with  the 
said  to  furnish  all  the  materials  and  labor,  and  in  a  good, 

firm,  and  substantial  manner  construct  [description  of  work] : 

Now,  therefore,  the  condition  of  the  above  obligation  is  such,  that 
if  the  said  above  bounden 

or  executors,   administrators,   or  assigns,  shall   well  and 

truly,  in  a  good,  sufficient,  and  workmanlike  manner,  perform  the 
work  mentioned  in  the  aforesaid  agreement,  in  accordance  with  the 
terms  and  provisions  therein  stipulated,  and  in  each  and  every  re- 
spect comply  with  the  conditions  and  covenants  therein  contained, 
then  this  obligation  to  be  void ;  otherwise  to  remain  in  full  force 
and  virtue. 


Signed  and  sealed  in  presence  of 


STATE  OF  ,  CITY  OF  ,  COUNTY  OF  ,ss.: 

On  this  day  of  ,  189  ,  before  me  personally  came 

to  me  personally  known,  and  known  to  me  to  be  the  same  persons 
described  in  and  who  executed  the  foregoing  obligation,  and  sev- 
erally acknowledged  that  they  executed  the  same. 


Commissioner  of  Deeds, 
County. 

STATE  OF  ,  CITY  OF  ,  COUNTY  OF  ,  ss.  : 

I  ,  of  said  ,  being  duly  sworn,  do  depose  and  say, 

that  I  am  a  holder  in  the  of  and  in 


SPECIFICATIONS    AND    CONTRACTS.  705 

said  ,  and  that  I  am  worth  the  sum  of  one  thousand  dollars 

over  and  above  all  my  debts  and  liabilities,  including  my  liabilities 
as  bail,  surety,  and  otherwise,  and  over  and  above  all  my  property 
which  is  exempt  by  law  from  execution. 
Subscribed  and  sworn  to  this  |_ 

day  of  ,  189  ,  before  me,       \ 


Commissioner  of  Deeds, 
County. 

103 la.  Specifications  for  Team  Labor. — timber  of  Horses  and 
Carts. — The  contractor  shall  at  all  times  be  prepared  to  supply 
after  twenty-four  hours'*  notice  given  by  the  county  engineer  or 
his  representative  to  the  contractor  or  his  representative  any  num- 
ber not  exceeding  horses,  carts,  trucks,  and  the 
necessary  attendants. 

Employment. — Whilst  the  horses,  vehicles,  and  attendants  are 
at  work  for  the  county  they  shall  be  under  the  direction  and 
orders  of  the  county  engineer  or  his  representative,  and  may  be 
used  for  any  kind  of  work  in  connection  with  the  (construction) 
(repair)  of  the  roads. 

Condition,  etc.,  of  Horses  and  Vehicles. — If  the  county  engineer 
is  of  the  opinion  that  any  horse,  vehicle,  or  attendant  supplied  by 
the  contractor  is  unfit  for  the  work,  and  shall  so  inform  him,  the 
contractor  shall  without  delay  provide  another  horse,  vehicle,  or 
attendant  to  the  satisfaction  of  the  engineer. 

Labor. — The  attendants  sent  with  the  horses  shall  in  every  case 
be  able-bodied  men  over  eighteen  years  of  age,  and  when  not  en- 
gaged in  handling  the  horses,  they  shall  assist  the  laborers  fill- 
ing the  vehicles. 

Hours. — The  horses  shall,  in  all  cases,  work  the  same  number 
of  hours  as  the  roadmen,  not  exceeding  hours  per  day. 

Time  for  watering,  etc.,  will  be  allowed,  not  exceeding  twenty 
minutes  in  the  forenoon  and  twenty  minutes  in  the  afternoon. 
One  hour  will  be  allowed  at  mid-day  for  feeding. 

Accidents. — During  the  time  the  horses  and  vehicles  are  em- 
ployed by  the  the  attendants  shall  under  no 
circumstances  leave  them.  The  contractor  shall  be  responsible  in 


70G  HIGHWAY   CONSTRUCTION". 

case  of  accident  owing  to  neglect,  carelessness,  or  inattention  on 
the  part  of  the  attendants. 

1031b.  Specifications  for  Sprinkling. — Amount  of  Work. — The 
work  to  be  done  consists  in  sprinkling,  in  the  manner  prescribed 
herein,  the  roadways  from  curb-line  to  curb-line  of  the  following- 
named  avenues,  streets,  and  public  places  of  the  city  of 
The  total  length  of  streets  to  be  sprinkled  under  these  specifica- 
tions is  estimated  at  miles. 

The  number  of  times  and  hours  of  sprinkling  shall  be  as  fol- 
lows: 

1.  All  streets,  avenues,  public  places,  and  parts  thereof  shall  be 
sprinkled  times  a  day  during  the  entire  season :  provided, 
that  only                   sprinklings  during  the  season  shall  be  required 
on  Sundays. 

2.  When  a  street  is  sprinkled  three  times  a  day,  the  first  sprink- 
ling shall  be  completed  before  8  o'clock  A.M.,  the  second  sprinkling 
shall  be   between  10  o'clock  A.M.  and  1  o'clock  P.M.,  and  the  third 
sprinkling  shall  be  between  2  o'clock  P.M.  and  6  o'clock  P.M. 

3.  When  four  sprinklings  a  day  are  required,  the  first  sprinkling 
shall  be  completed  before  8  A.M.,  the  second  shall  be  between  8  A.M. 
and  11  A.M.,  the  third  shall  be  between  12  noon  and  3  P.M.,  and  the 
fourth  shall  be  between  3  P.M.  and  6  P.M. 

4.  All  streets  shall  be  sprinkled  in  regular  rotation.  The  starting- 
point  in  the  morning  shall  be  the  starting-point  for  all  the  follow- 
ing sprinklings  during  the  day. 

5.  The  quantity  of  water  to  be  delivered  on  the  street  will  be 
determined  from  time  to  time  by  the  Street  Commissioner. 

6.  The  sprinkling  shall  be  done  with  two-horse  wagons  which 
carry  a  tank  holding  not  less  than  600  gallons,  and  shall  have 
attached   two   sprinklers.     The    wagons   must   be   provided   with 
springs   (fore  and  aft),  and  must  have  tires   not  less  than  three 
inches  in  width.     The  wagons  must  also  be  numbered  consecutively, 
and  have  the  name  of  the  contractor  in  letters  not  less  than  three 
inches  in  height  painted  on  the  rear  end  of  the  tank. 

7.  The  sprinklers  must  be  so  arranged  that  the  spray  of  water 
can  be  readily  stopped  by  the  driver  on  either  side  of  the  wagon. 
The  sprinklers  shall  be  constructed  so  as  to  deliver  and  properly 
spread  the  water,  and  be  provided  with  suitable  controlling  devices 


SPECIFICATIONS   AND   CONTRACTS.  707 


for  regulating  the  quantity  of  water  discharged,  said  devices  to  he 
so  arranged  as  to  be  operated  by  the  driver  from  the  seat  or  foot- 
board; the  spray  of  water  thrown  must  be  uniform  throughout  its 
entire  width. 

The  sprinklers  must  be  kept  in  good  condition  and  repair, 
Wagons  with  broken  or  choked  sprinklers,  defective  gear,  and  leak- 
ing tanks  or  valves  shall  not  be  used. 

8.  All  wagons  shall  be  periodically  inspected,  and  any  found 
unfit  for  use  shall  be  ordered  off  the  street,  and  sprinkling  done  by 
rejected  wagons  will  not  be  paid  for. 

9.  Sprinkling  must  be  done  with  judgment  and  care,  and  the 
street-crossings  must  be  kept  as  nearly  dry  as  possible. 

10.  If  the  contractor  fails  or  neglects  to  sprinkle  any  street  or 
avenue  the  number  of  times  required  by  this  contract  except  in 
case  of  rain,  or  if  he  should  flood  the  street  or  avenue,  then  two- 
thirtieths  of  his  monthly  pay  for  said  street   or  avenue  will  be 
deducted  for  each  day  on  which  such  omission  or  flooding  occurs. 

11.  As  to  whether  the  contractor  has  given  the   streets   the 
number  of  sprinklings  and  the  quantity  of  water  required,  and  as 
to  whether  rain  has  obviated  the  necessity  of  sprinkling,  shall  be 
determined  by  the  Street  Commissioner. 

12.  The  contractor  shall  use  particular  care  not  to  waste  any 
water  in  filling  the  tanks;  and  also  in  closing  the  hydrants  as  soon 
as  the  tank  has  been  filled.     A  deduction  of  two  dollars  shall  be 
made  on  the  next  monthly  estimate  for  every  hydrant  which  is  left 
wholly  or  partly  open  when  not  in  use  for  filling  the  tank.     Any 
hydrant  found  damaged  or  out  of  order  must  be  immediately  re- 
ported  to  the  Street  Commissioner.     Hydrants  damaged  by  the 
contractor   shall   be   repaired   by  the  Water  Commissioner,   who 
will  report  the  cost  to  the  Street  Commissioner,  who  will  charge  it 
to  the  contractor  and  deduct  it  from  his  monthly  estimate. 

1031c.  Form  of  Monthly  Certificate. 

CERTIFICATE  No. 

$  City  of  ,  19 

To 

THIS  is  TO  CERTIFY  that  under  the  terms  of  the  contract 
dated  ,  for  work  upon 


708  HIGHWAY  CONSTRUCTION. 

Mr.  ,  contractor,  is  entitled  to  the   following  pay- 

ment, amounting  to  T¥¥  Dollars. 

The  above  estimate  is  based  on  Ain't  of  this  cer- 

tificate $ 

Previously  paid  $ 

Total  paid  to  date  $ 


Engineer  in  charge. 
103 Id.  Affidavit  of  Contractor. 

State  of  ,  City  of  ,  ss  : 

,  being  duly  sworn  according  to  law,  on 

his  oath  saith  that  he  is  the  contractor  mentioned  in   a  certain 
agreement  made  with  the  Mayor  and  Common  Council  of 
for  the  improving  and  paving  of  from  to 

in  said  city,  and  that  the  work  thereon  has  been  completed  and 
finished  according  to  the  terms  and  conditions  of  said  agreement 
in  every  particular. 

And  deponent  further  saith  that  all  the  laborers  and  workmen 
employed  by  him  on  said  work,  and  all  and  every  person  or  persons 
who  have  furnished  materials,  have  been  paid,  and  that  he  does  not 
now  owe  anything  for  materials  furnished  or  to  any  laborers  or 
workmen  or  other  persons  for  work  or  labor  done  or  performed  by 
them  on  said  work. 

And  deponent  further  saith  that  there  has  been  no  damage  done 
or  injury  sustained  by  any  person  or  persons  either  to  themselves 
or  their  property,  which  was  caused  by  reason  of  any  act,  omission, 
carelessness,  or  want  of  skill  on  the  part  of  this  deponent  or  his 
agents  in  the  prosecution  of  the  work  aforesaid,  and  that  no  notice 
has  been  served  upon  him  or  any  claims  or  demand  has  been  made 
upon  him  for  damages  thereunder,  and  deponent  knows  of  no 
claim  or  demand  that  any  person  or  persons  have  or  can  have 
against  him  or  said  city  for  any  damage  caused  or  injury  done  to 
themselves  or  their  property  during  the  construction  of  the  afore- 
said work. 

Sworn  and  subscribed  to    before  / 
me  this        day  of  ,19        ,  ( 


SPECIFICATIONS   AND    CONTRACTS.  709 

103 le.  Certificate  of  Acceptance. 
To  THE  MAYOR  AND  COMMON  COUNCIL  OF  THE  CITY  OF  : 

I  do  hereby  certify  that  of  from 

to  ,  contractor,  has  been  completed  to  my  satisfaction 

and  in  accordance  with  the  specifications  and  contract. 


Engineer  in  charge. 

103 If.  Certificate  of  Final  Acceptance. 
To  THE  MAYOR  AND  COMMON  COUNCIL  OF  THE  CITY  OF  : 

,19 

I  do  hereby  certify  that  the  year(s)  during  which  period 

the  pavement  of  from  to  , 

M  ,  contractor,  was  required  to  be  kept  in  repair,  expired 

on  ,  19 

As  the  proper  repairs  have  been  made,  and  the  work  is  now  in 
a  condition  satisfactory  to  me  and  in  accordance  with  the  specifi- 
cations and  contract,  the  ten  per  cent  retained  is  now  due  and 
payable,  for  which  amount  I  have  given  a  certificate  this  day. 


Engineer  in  charge. 


CHAPTER  XXIII. 


TOOLS  AND   MACHINERY   EMPLOYED    IN    THE    CONSTRUCTION 

OF  -HIGHWAYS. 

THE  implements  employed  in  the  construction  of  highways  and 
pavements  are  many  and  varied.  A  brief  description  of  the  prin- 
cipal ones,  and  the  range  in  price,  is  given  in  the  following  pages. 
The  prices  stated  are  only  approximate  and  will  vary,  depending 
upon  the  quantitv  required  and  the  condition  of  the  market. 

1032.     Tools  for  Clearing  and  Grubbing. 


FIG.  186.— BUSH-HOOKS. 


FIG.  187. — AXE  MATTOCK. 


FIG.  188.— PICK  MATTOCK. 


Axes price  per  dozen  $12.00  to  $15.50 

Bush-hooks,  bandied "      "        "        17.00 

Grub-hoes "      "        "        11.00  to    17.00 

Mattocks "      "        "        15.50"    18.00 

Stump-pulling  machines each  150.00  "  250.00 

Cross-cut  saws per  foot      0.68 

710 


TOOLS    AND    MACHINERY    EMPLOYED. 


711 


1033.  Tools  for  Grading. — PICKS  are  made  of  various  styles,  ac- 
cording to  the  class  of  material  in  which  they  are  to  be  used. 
Fig.  189  shows  the  form  usually  employed  in  street  work.  Fig.  190 
shows  the  form  generally  used  for  clay  or  gravel  excavation. 

The  eye  of  the  pick  is  generally  formed  of  wrought  iron,  pointed 
with  steel. 

The  weight  of  picks  ranges  from  4  to  9  Ibs.,  and  cost  per  dozen 
$8.50  to  $25. 


FIG.  189. — GRADING-PICK. 


FIG.  190.— CLAY-PICK. 


SHOVELS  are  made 'm  two  forms,  square-  and  round-pointed, 
usually  of  pressed  steel.  They  cost  from  $7  to  $13  per  dozen  for 
the  square-pointed  and  from  $7.25  to  $13.50  for  the  round-pointed. 


FIG.  191.— SHOVELS. 


PLOUGHS  are  extensively  employed  in  grading,  special  forms 
being  manufactured  for  the  purpose.  They  are  known  as  "  grading- 
ploughs,"  "road-ploughs,"  "breaking-ploughs,"  "township-ploughs,"1 
etc.  They  vary  in  form  according  to  the  kind  of  work  they  are 
intended  for,  viz.,  loosening  earth,  gravel,  hardpan,  and  some  of 
the  softer  rocks. 

These  ploughs  are  made  of  great  strength,  selected  white  oakr 
rock  elm,  wrought  steel  and  iron  being  generally  used  in  their  con- 
struction. 

The  cost  of  operating  ploughs  ranges  from  2  to  5  cents  per 
cubic  yard,  depending  upon  the  compactness  of  the  soil. 


712  HIGHWAY   CONSTRUCTION. 

The  quantity  of  material  loosened  will  vary  from  2  to  5  cubic 
yards  per  hour. 

Fig.  192  shows  the  form  usually  adopted  for  loosening  earth. 
This  plough  does  not  turn  the  soil,  but  cuts  a  furrow  about  10  inches 


FIG.  192. — GKADING-PLOUGH. 

wide  and  of  such  a  depth  as  it  may  be  regulated  for  up  to  11  inches. 

In  light  soils  the  ploughs  are  operated  by  two  or  four  horses;  in 
heavy  soils  as  many  as  eight  are  employed. 

Grading-ploughs  vary  in  weight  from  100  to  325  Ibs.,  in  price 
from  $22  to  $65. 

Fig.  193  illustrates  a  plough  specially  designed  for  tearing  up 
macadam,  gravel,  or  similar  material.  The  point  is  a  straight  bar 
of  cast  steel  drawn  down  to  a  point,  and  can  be  easily  repaired. 
Price  about  $40. 


FIG.  193.— HARDPAN-PLOUGH. 


TOOLS   AND   MACHINERY    EMPLOYED. 


13 


SCRAPERS  are  generally  used,  to  move  the  material  loosened  by 
ploughing;  they  are  made  of  either  iron  or  steel,  and  in  a  variety  of 
forms,  and  are  known  by  various  names,  as  "drag,"  "buck/* 
<( pole/'  and  "wheeled." 

The  drag-scrapers  are  usually  employed  on  short  hauls,  the 
wheeled  on  long  hauls. 

Figs.  194  and  195  illustrate  the  usual  form  of  drag-scrapers. 


FIG.  194.— DRAG-SCRAPER. 

Drag-scrapers  are  made  in  three  sizes.  The  smallest,  for  one 
horse,  has  a  capacity  of  3  cubic  feet;  the  others,  for  two  horses, 
have  a  capacity  of  5  to  7-J  cubic  feet.  The  smallest  weighs  about 
90  Ibs.,  and  the  larger  ones  from  94  to  102  Ibs. 


FIG.  195. — DRAG- SCRAPER  WITH  RUNNERS. 


u 


HIGHWAY    CONSTKUCTION". 


The  price  is  variable,  iron  being  the  cheapest  and  steel  the 
dearest;  the  range  appears  to  be  from  $10  to  $18. 

A  recent  improvement  in  drag-scrapers  is  the  furnishing  them 
with  runners  or  a  double  bottom.  These  devices  prolong  the  life 
of  the  scraper.  Fig.  195  shows  a  drag-scraper  furnished  with  steel 
runners. 

Buck-scrapers  are  made  in  two  sizes — two-horse,  carrying  7-J 
cubic  feet ;  four-horse,  12  cubic  feet. 

Pole-scraper  Fig.  196  is  designed  for  use  in  making  and  levell- 
ing earth  roads  and  for  cutting  and  cleaning  ditches;  it  is  alsa 
well  adapted  for  moving  earth  short  distances  at  a  minimum 
cost. 


FIG.  196— POLE-SCRAPER. 


SIZE  AND  PRICE. 

48  in.  wide,  weight  123  Ibs : $14 

86"      "  "       113" 13 

Wheeled  scrapers  consist  of  a  metal  box,  usually  steel,  mounted 
on  wheels,  and  furnished  with  levers  for  raising,  lowering,  and 
dumping.  They  are  operated  in  the  same  manner  as  drag  scrapers, 
except  that  all  the  movements  are  made  by  means  of  the  levers, 
and  without  stopping  the  team.  By  their  use  the  excessive  resist- 
ance to  traction  of  the  drag-scraper  is  avoided.  Various  sizes  are 
made,  ranging  in  capacity  from  10  to  17  cubic  feet.  In  weight  they 
range  from  350  to  700  Ibs. ;  in  price  from  $40  to  $75. 

Figs.  197  to  199  show  the  three  positions  of  the  scrapers  when 
in  use. 


TOOLS   AND    MACHINERY    EMPLOYED. 


715 


FIG.  197.— POSITION  WHEN  LOADING. 


FIG.  198.— POSITION  WHEN  CARRYING 


FIG.  199. — POSITION  WHEN  UNLOADED. 


716 


HIGHWAY    CONSTRUCTION. 


WHEELBARROWS. — The  wheelbarrow  Fig.  200  is  constructed  of 
wood  and  is  the  one  most  commonly  employed  for  earthwork.  Its 
capacity  ranges  from  2  to  2-J-  cubic  feet.  Weight  about  50  Ibs. 
Price  about  $20  per  dozen. 

The  barrow  Fig.  201  has  a  pressed-steel  tray,  oak  frame,  and  steel 
wheel,  and  will  be  found  more  durable  in  the  maintenance  depart- 
ment than  the  all-wood  barrow.  Capacity  from  3£  to  5  cubic  feet, 
depending  on  size  of  tray.  Price  from  $5.50  to  $7.50. 

The  barrow  Fig.  202  is  constructed  with  tubular  iron  frames  and 
steel  tray,  and  is  adaptable  to  the  heaviest  work,  such  as  moving 
heavy  broken  stone,  etc.,  or  it  may  be  employed  witli  advantage  in 
the  cleaning  department.  Capacity  from  3  to  4  cubic  feet.  Weight 
from  70  to  82  Ibs.  Price  from  $10.75  to  $13.50. 


FIG.  200. 


FIG.  201 


FIG.  202. 

The  maximum  distance  to  which  earth  can  be  wheeled  economi- 
cally in  barrows  is  about  200  feet. 

The  wheeling  should  be  performed  upon  planks,  whose  steepest 
inclination  should  not  exceed  1  in  12.  The  power  required  to  move 
a  barrow  on  a  plank  is  about  *fa  part  of  the  weight;  on  hard  dry 
earth,  about  T^  part  of  the  weight. 

The  time  occupied  in  loading  a  barrow  will  vary  with  the  char- 
acter of  the  material  and  the  proportion  of  wheelers  to  shovellers. 
Approximately,  a  shoveller  takes  about  as  long  to  fill  a  barrow  with 
earth  as  a  wheeler  takes  to  wheel  a  full  barrow  a  distance  of  about 


TOOLS   AND   MACHINERY    EMPLOYED. 


100  or  120  feet  on  a  horizontal  plank  and  return  with  the  empty 
barrow. 

CARTS. — The  cart  usually  employed  for  hauling  earth,  etc.,  is 
shown  in  Fig.  203.  The  average  capacity  is  22  cubic  feet,  and  the 
average  weight  is  800  Ibs.  Price  about  $75. 

These  carts  are  usually  furnished  with  broad  tires,  and  the  body 
is  so  balanced  that  the  load  is  evenly  divided  above  the  axle. 

The  time  required  to  load  a  cart  varies  with  the  material.  One 
shoveller  will  require  about  as  follows  :  clay,  seven  minutes  ;  loam, 
six  minutes  ;  sand,  five  minutes. 


FIG.  203.—  EARTH-CART. 

DUMP-CARS. — These  cars  are  made  to  dump  in  several  different 
ways,  viz.,  single  or  double  side,  single  or  double  end,  and  rotary 
or  universal  dumpers. 

Dump-cars  may  be  operated  singly  or  in  trains,  as  the  magni- 
tude of  the  work  may  demand.  They  may  be  moved  by  horses  or 
small  locomotives.  They  are  made  in  various  sizes,  depending  upon 
the  gauge  of  the  track  on  which  they  are  run.  A  common  gauge  is 
20  inches,  but  varies  from  that  up  to  the  standard  railroad  gauge 
of  56£  inches. 

The  principal  dimensions,  Capacity,  prices,  etc.,  of  single-side 
dumping-cars  are  given  in  the  following  table.  Those  made  by 
different  manufacturers  vary,  but  not  materially,  from  these  stated. 


18 


HIGHWAY    CONSTRUCTION. 


TOOLS   AND   MACHINERY   EMPLOYED. 


FIG.  205.— ROTARY  DUMPING-CAR. 


DIMENSIONS,   CAPACITY,   PRICES,   ETC.,    OF  DUMP-CARS. 


Dimensions. 

Gausre. 
Inches. 

b 

OJ 

5 

JS 

¥ 

U  aj 

0>  $ 

S" 

Length  of 
Body. 

Width. 

! 

^•d 

O  p^ 

® 

•s| 

r 

Diameter  of 
Wheels. 

Diameter  of 
Axles. 

i 

« 

£  ' 

I 

u  3 

3 

Price. 

ft.  in. 

ft.  in. 

ft.  in. 

ft.  in. 

in. 

ft.  in. 

in. 

in. 

Ibs. 

20 

7    5 

3    3 

5    0 

5    0 

16 

4    0 

16 

tf 

1300 

II 

$64 

30 

" 

•' 

" 

" 

;; 

" 

" 

1400 

67 

36 

•i 

H 

*  ^ 

k* 

*' 

1450 

'* 

70 

36  to  56* 

8    4 

3    5 

6    0 

6    0 

24  to  30 

" 

20 

" 

2000 

2frto3 

100  to  110 

TRACK  AND  TRACK  FASTENINGS. — The  rails  used  on  con- 
struction range  from  12  to  25  Ibs.  per  yard.  The  price  varies  con- 
siderably with  th6  condition  of  the  market. 


720 


HIGHWAY    CONSTRUCTION. 


The  number  of  tons  of  rails  required  per  mile  is  as  follows: 


Weightperyard. 

121bs  ____  .....................................  IStons  1920  Ibs. 

16  "  .........................................  25     "  320  " 

20"  .........................................  31     "  960" 

25  "  ........................................  39    "  640  " 

28"  .........................................  44     "  000" 

The  number  of  cross-ties  per  mile  is  as  follows  : 

Centre  to  Centre.  No.  of  Ties 

Hfeet...  ...............................................  3.520 

If    "  ..................................................  3.017 

2      "  ................................................  2.640 

.  2J.    "  ..............................................   ...  2.348 

2£    "  ..................................................  2.113 

The  number  of  splice-joints  per  mile  is  as  follows  (two  bars 
and  four  bolts  and  nuts  to  each  joint)  : 

Rails  20  feet  long  ......................  ...............  528  joints 

"    24    "      "    ......................................  440      " 

"    26    "       "    ......................................  406      " 

"    28    "       "    ......................................  378      " 

"    30    "      "    ......................................  352      " 


The  size  of  spikes  used  and  the  number  required  per  mile  is  as 
follows  (four  spikes  per  tie)  :  . 


Weight  of  Rail. 


24  to  35  Ibs. 
20  to  30  " 
16  to  25  " 
16  to  20  " 
16  to  20  " 
12  to  16  " 


Size,  measured 
under  head. 


4"  x  r 

4    XT7* 
4    XI 


Ties,  2  ft. 

C.  to  C., 

require  Kegs 


17* 
14f 
10* 


7* 


Average  Number 
per  Keg  of  200  Ibs. 


600 
720 
1000 
1190 
1240 
1342 


DUMP-WAGONS,  Figs.  206  and  207.— The  use  of  these  wagons 
for  moving  excavated  earth,  etc.,  and  for  transporting  materials 
euch  as  sand,  gravel,  etc.,  materially  shortens  the  time  required  for 


TOOLS   AtfD    MACHINERY    EMPLOYED. 


721 


unloading  the  ordinary  form  of  contractor's  wagon ;  having  no  reach 
•or  pole  connecting  the  rear  axle  with  the  centre  bearing  of  the  front 
axle,  they  may  be  cramped  short  and  the  load  deposited  just 


FIG.  206.— DUMP- WAGON. 


FIG.  207. — DUMP-WAGON  DUMPED. 


799 


HIGHWAY    CONSTRUCTION. 


where  required.     They  are  operated  by  the  driver,  and  the  capacity 
ranges  from  35  to  45  cubic  feet. 

MECHANICAL   GRADERS. — Within   the  last  few  years  several 
machines  have  been  devised  for  the  purpose  of  handling  earth  more 


FlG.    208. — ROAD- GRADER. 

expeditiously  and  economically  than  can  be  done  by  hand;  they 
are  called  by  various  names,  such  as  "  road  machines,"  e<  graders/' 
" road-hones,"  etc.  Their  general  form  is  shown  in  Figs.  208  to 
210. 


FlG.  209.— liO AD- GRADER. 


Briefly  described,  they  consist  of  a  large  blade  made  entirely  of 
steel  or  of  iron,  or  wood  shod  with  steel,  which  is  so  arranged  by 
mechanism  attached  to  the  frame  from  which  it  is  suspended  that 


TOOLS   AND   MACHINERY    EMPLOYED.  723 

it  can  be  adjusted  and  fixed  in  any  direction  by  the  operator.  In 
their  action  they  combine  the  work  of  excavating  and  transporting 
the  earth.  They  have  been  chiefly  employed  in  the  forming  and 
maintenance  of  earth  roads,  but  may  be  also  advantageously  used 
in  preparing  the  subgrade  surface  of  roads  for  the  reception  of 
broken  stone  or  other  improved  covering. 

A  large  variety  of  such  machines  are  on  the  market,  and  the 
price  ranges  from  $100  to  $300. 


FIG.  210.— ROAD-GRADER. 

Besides  the  above-described  machines,  there  is  another  known  as 
the  "New  Era"  grader,  shown  in  Fig.  211.  This  machine  ex- 
cavates the  material  from  side  ditches,  and  automatically  places  it 
in  the  embankment,  or  it  can  be  used  in  a  cutting,  in  which  situ- 
ation it  will  excavate  and  automatically  load  the  material  into  carts 
or  wagons.  Fig.  212  shows  the  machine  at  work. 

Briefly  described,  the  machine  consists  of  a  plough  which 
loosens  and  raises  the  earth,  depositing  it  upon  a  transverse  carry- 
ing-belt, which  conveys  it  from  excavation  to  embankment.  This 
carrier  is  built  in  four  sections,  bolting  together,  so  it  can  be  used 
to  deliver  earth  at  14,  17,  19,  or  22  feet  from  the  plough.  The 
carrier-belt  is  of  heavy  3-ply  rubber  3  feet  wide. 

The  plough  and  carrier  are  supported  by  a  strong  trussed  frame- 
work resting  on  heavy  steel  axles  and  broad  wheels.  The  large 
rear  wheels  are  ratcheted  upon  the  axle3  and  connected  with  strong 


724 


HIGHWAY   CONSTRUCTION". 


gearing  which    propels   the   carrying-belt   at   right   angles   to  the 
direction  in  which  the  machine  is  moving. 


FIG.  211.— NEW  ERA  GRADER. 


FIG.  212.— NEW  ERA  GRADER  AT  WORK. 

The  wheels  and  trusses  are  low  and  broad,  occupying  a  space  8 
feet  wide  and  14  feet  long,  exclusive  of  the  side  carrier.  This  en- 
ables it  to  work  on  hillsides  where  any  wheeled  implement  can  be 


TOOLS    AND    MACHINERY    EMPLOYED. 


used.  Notwithstanding  its  large  size  it  is  so  flexible  that  it  may  be 
turned  around  on  a  16-foot  embankment.  Pilot-wheels  and  levers 
enable  the  operator  to  raise  or  lower  the  plough  or  carrier  at 
pleasure. 

As  a  motive  power  12  horses — 8  driven  in  front,  4  abreast,  and 
4  in  the  rear  on  a  push-cart — are  usually  employed. 

When  the  teams  are  started,  the  operator  lowers  the  plough  and 
throws  the  belting  into  gear,  and  as  the  plough  raises  and  turns  the 
earth  to  the  side  the  belt  receives  and  delivers  it  at  the  distance 
for  which  the  carrier  is  adjusted,  forming  either  excavation  or 
embankment. 

When  it  becomes  necessary  to  deliver  the  excavated  earth  be- 
yond the  capacity  of  the  machine  (22  feet  or  7J-  feet  above  the 
plough),  the  earth  is  loaded  upon  wagons,  then  conveyed  to  any 
distance.  Arranging  the  carrier  at  19  feet,  wagons  are  driven 
under  the  carrier  and  loaded  with  1£  to  1^  yards  of  earth  in  from 
20  to  30  seconds.  When  one  wagon  turns  out  with  its  load,  an- 
other drives  under  the  carrier,  and  the  machine  thus  loads  600  to 
800  wagons  per  day. 

The  makers  claim  that  with  six  teams  and  three  men  it  is  capa- 
ble of  excavating  and  placing  in  embankment  from  1000  to  1500 
cubic  yards  of  earth  in  ten  hours,  or  of  loading  from  600  to  800 
wagons  in  the  same  time,  and  that  the  cost  of  this  handling  is 
from  1 J  to  2^  cents  per  cubic  yard. 

POINTS  TO  BE  CONSIDERED  IN  SELECTING  A  EOAD  MACHINE. 
— In  the  selection  of  a  road  machine  the  following  points  should  be 
carefully  considered: 

(1)  Thoroughness  and  simplicity  of  its  mechanical  construction. 

(2)  Material  and  workmanship  used  in  its  construction. 

(3)  Ease  of  operation. 

(4)  Lightness  of  draft. 

(5)  Adaptability  for  doing  general  road-work,  ditching,  etc. 

(6)  Safety  to  the  operator. 

CARE  OF  EOAD  MACHINES. — The  road  machine  when  not  in 
use  should  be  stored  in  a  dry  house  and  thoroughly  cleaned,  its 
blade  brushed  free  from  all  accumulations  of  mud,  wiped  thor- 
oughly dry,  and  well  covered  with  grease  or  crude  oil.  The  axles, 
journals,  and  wearing  parts  should  be  kept  well  oiled  when  in  use, 


726  HIGHWAY    CONSTRUCTION. 

and  the  blade  should  be  kept  sharp  and  in  good  condition  at  all 
times.  An  extra  blade  should  be  kept  on  hand  to  avoid  stopping 
the  machine  while  the  dulled  one  is  being  sharpened. 

SURFACE-GRADERS. — The  surface-grader,  Fig.  213,  is  used  for 
removing  earth  previously  loosened  by  a  plough.  It  is  operated  by 
one  horse.  The  load  may  be  retained  and  carried  a  considerable 


FIG.  213.— SURF  ACE- GRABEK. 


distance,  or  it  may  be  spread  gradually,  as  the  operator  desires.     It 
is  also  employed  to  level  off  and  trim  the  surface  after  scrapers. 

The  blade  is  of  steel,  J  inch  thick,  15  inches  wide,  and  30  inches 
long.  The  beam  and  other  parts  are  of  oak  and  iron.  Weight 
about  60  Ibs.  Price  about  $9. 


FIG.  214. — ROAD-LEVELLER. 

The  road-leveller,  Fig.  214,  is  used  for  trimming  and  smoothing 
the  surface  of  earth  roads.  It  is  largely  employed  in  the  spring 
when  the  frost  leaves  the  ground. 

The  blade  is  of  steel,  £  inch  thick  by  4  inches  by  72  inches,  and 
is  provided  with  a  seat  for  the  driver.  It  is  operated  by  a  team  of 
horses.  Weight  about  150  Ibs.  Price  about  $12. 


TOOLS   AND   MACHINERY   EMPLOYED. 


72^ 


1034.  Draining-tools. — The  tools  employed  for  digging  the 
ditches  and  shaping  the  bottom  to  fit  the  drain-tiles  are  shown  in 
Fig.  215.  They  are  convenient  to  use,  and  expedite  the  work  by 
avoiding  unnecessary  excavation.  For  cost  of  drains,  etc.,  see  Art. 

688,  et  seq. 


No.i. 


No.  T 


FIG.  215. — DKAINING-TOOLS. 


The  tools  are  used  as  follows :  Nos.  3,  4,  and  5  are  used  for 
digging  the  ditch;  Nos.  6  and  7  for  cleaning  and  rounding  the 
bottom  of  the  ditch  for  round  tile.  No.  2  is  used  for  shovelling 
out  loose  earth  and  levelling  the  bottom  of  the  ditch;  No.  1  is 
used  for  the  same  purpose  when  the  ditch  is  intended  for  "  sole  " 
tile. 


728  HIGHWAY    CONSTRUCTION. 

1035.  Tools  for  Rock  Excavation — HAND  DRILLING. — The  tools 
employed  for  hand  drilling  are  illustrated  in  Fig.  216,  in  which  Fig. 
A  represents  the  first  or  shortest  drill,  usually  eighteen  inches  in 
length,  with  cutting  head  about  one  and  three  quarter  inches  wide 
and  weight  about  four  pounds.  The  second  drill  is  shown  by  Fig.  B; 
it  is  about  twenty-seven  inches  long,  one  and  eleven  sixteenth 
inches  wide  on  the  cutting  edge,  and  weighs  about  six  pounds. 
The  third  or  longest  drill  is  shown  at  C ;  it  is  usually  forty  inches 
in  length,  cutting  edge  one  and  five  eighth  inches  wide,  and  weighs 
about  nine  pounds. 

The  scraper  is  shown  by  Fig.  D.  It  is  used  to  remove  the  sludge 
,  from  the  bottom  of  the  hole,  and  consists  of  an  iron  rod  one  half 
inch  in  diameter,  one  end  of  which  is  flattened  out  in  a  circular 
form  and  turned  up  at  right  angles  to  the  stem.  The  other  end  is. 
made  to  terminate  in  a  spiral  hook  or  drag-twist,  the  use  of  which 
is  to  withdraw  the  absorbent  material  used  to  dry  the  hole  before 
inserting  the  explosive. 

The  butt  or  daying-iron  is  shown  by  Fig.  E.  It  is  used  for  forc- 
ing clay  into  seamy  rock  and  thus  prevent  the  entrance  of  water 
into  the  blast-hole.  It  consists  of  a  round  bar  of  iron,  called  the 
stock  or  shaft,  a  little  smaller  in  diameter  than  the  bore-hole,  and 
a  thicker  portion,  called  the  head  or  poll,  terminating  in  a  striking- 
face.  While  this  tool  is  not  an  essential  part  of  a  drilling  outfit, 
yet  it  is  a  very  serviceable  one,  and  should  always  be  at  hand  in  wet 
ground  when  loose  gunpowder  is  employed. 

Fig.  F  represents  the  tamping-iron  or  rammer.  It  consists  of  a 
bar  of  copper  or  phosphor  bronze,  the  tamping  end  of  which  is 
grooved  to  receive  the  fuse  lying  against  the  side  of  the  bore-hole. 
The  use  of  rammers  made  of  iron  is  dangerous,  as  sparks  produced 
by  the  striking  of  the  iron  against  silicious  substances  may  cause 
ignition  of  the  charge. 

Fig.  G  represents  an  auxiliary  implement  called  the  heche.  It 
is  used  for  extracting  a  broken  drill.  It  consists  of  an  iron  rod 
having  a  diameter  slightly  less  than  that  of  the  bore-hole,  and  is 
made  hollow  at  one  end.  The  form  of  the  aperture  is  slightly  con- 
ical, so  that  it  may  pass  over  the  broken  stock  of  the  drill,  and  when 
hammered  down  may  grasp  the  stock  in  its  higher  portion  with 
sufficient  firmness  to  allow  of  the  two  being  drawn  out  together. 


TOOLS   AND    MACHINERY    EMPLOYED. 


o 

lib 


to 


|LJ 

to 


o       O 


FIG.  216. — HAND-DRILLING  TOOLS. 


to 


730  HIGHWAY   CONSTRUCTION-. 

Fig.  H  represents  the  sledge  or  striking-hammer;  its  form  and 
weight  are  variable,  the  latter  is  usually  about  five  pounds. 

Fig.  I  represents  the  hand  hammer;  its  weight  varies  from  two 
to  four  pounds.  The  distinction  between  a  hammer  and  a  sledge 
is  founded  on  dimensions  only;  the  hammer,  being  intended  for  use 
in  one  hand,  is  made  comparatively  light  and  is  furnished  with  a 
short  handle,  while  the  sledge,  being  intended  for  use  in  both  hands, 
is  furnished  with  a  much  longer  handle  and  is  made  heavier. 

Hand  drills  are  used  in  sets  of  different  lengths.  The  sets  may 
be  intended  for  use  by  one  man  or  by  two.  In  the  former  case 
the  sets  are  described  as  "  single-hand "  sets,  and  they  contain  a 
hammer  for  striking  the  drills;  in  the  latter  case  the  sets  are  called 
"  double-hand,"  and  they  contain  a  sledge  instead  of  a  hammer  for 
striking.  It  may  appear  at  first  sight  that  there  is  a  waste  of 
power  in  employing  two  men,  for  that  two  men  cannot  bore  as  fast 
as  one.  This  rate  of  speed  can,  however,  be  obtained,  and  is  due 
less  to  the  greater  effectiveness  of  the  stroke  than  to  the  fact  that 
two  men  can,  by  repeatedly  changing  places  with  each  other,  keep 
up  almost  without  intermission  a  succession  of  blows  for  an  indefi- 
nite length  of  time,  whereas  with  the  single  set  the  man  is  con- 
tinually obliged  to  cease  for  rest. 

The  making  and  resharpening  of  the  drills  is  an  extremely 
important  part  of  the  blacksmith's  labor  and  requires  judgment 
and  intelligence.  A  smith  will,  with  the  assistance  of  a  striker, 
sharpen  and  temper  about  thirty  single-hand  drills  of  medium  size 
in  an  hour,  or  twenty  double-hand  drills  of  medium  size  in  the 
same  time.  Of  course  much  will  depend  on  the  degree  of  blunt- 
ness  in  the  cutting  edge;  but  assuming  the  drills  to  be  sent  up  only 
moderately  blunted,  this  may  be  taken  as  a  fair  average  of  the 
work  of  two  men. 

PRICES  OF  HAND-DRILLING  TOOLS. 

Drill-steel per  pound  $0.25 

Striking-hammers,  3  to  5  pounds ..."         "          .36 

"  "         5  pounds  and  over "        "          .30 

Spoons each    2.00 

Wedges per  pound      .12$ 

Plug  and  feathers "        "          .30 

Crowbars "        "      !    .10 

Stone-sledges... "        "          .30 

Blacksmith  outfit from  $50  upwards 


TOOLS    AXI)    MACHINERY    EMPLOYED. 


STEAM  DRILLIXG. — A  steam-drilling  outfit  comprises  a  steam 
drill;  a  set  of  drill-steels;  a  sot  of  blacksmith's  tools  for  sharpening 
the  drills;  a  sand-pump;  a  band  for  centring  piston;  extra  drill 
parts;  a  portable  steam  boiler;  steam  hose.  etc. 


FIG.  217. — STEAM  DKILL. 


Steam  drills  vary  in  size,  price,  etc.,  as  shown  in  the  following 
table : 


•>-  p    .    .    .-•-»• 

CO 


00^ 

"5 


_) 
•J 

hH 

K 
P 

SH 

2 

<J 


w 


w 


oi 
2 
O 

•—  » 

h 
<3 
o 


O 

w 


v  t1  X1       ^  x+     X?  X'                      o  o  o  o    • 

>-\  -  \        O  -T,        «-\  ~\                              O    O    —    i-^     - 

O    O      •       G 

^2 

X 

TT  t^-O   ••"'    M    O    >-    >-"    r->          10             LO  -f  LO  Tt-     . 
ro0          i^ 

X 

810    .       LO 
'O            O 

5 

N 

~f. 

0 

— 

•5- 

c 

.« 

3 

•-fs. 

•-•x  \N                        xc«  %-f.                              O   "•*•  O    M-  i-o 

y,   x   x 

o  o  o     o 
o  o  o     o 

B 

0^ 

ro  l^  O    O    w    O    >-    -i    M          M              ro  ro  "-)  f  l    -f 
ro  ri          r^,                           w                                - 

CO    -    -4- 

000       0 

LOO  O       - 

< 

X 

LO  in  ro 

ta 

^.j 

^ 

> 

ro  O    "t 

"So 

j$ 

X-4-x  -t                  '    -f            '""'            \N                                    O     LOVO     i-     C\ 

•-^•^              w^         •—         i-l\                         c\  (^  ro  O    « 
roo    ^-iOi-OO««          o              n«    rocc    ro 
N    «-i          t^    ^                     ••* 

XXX 
XXX 

000 
l-o  O    O      LO 

^ 

*  i 

CC    LO  -<t 

r-i                   r<~. 

* 

•w 

>o 

M    O    -t 

i-     i-     Cl 

XXX 

52  3 

888    8 

1 

4? 

r-l    0          i^ 

CO    "1  TJ- 
-  CC    rf 

»o  LO  >o     o 

S 

s  ^ 

O                                                       -i- 

XXX 

O    O    O       O 

o  o  o     o 

^T 

s  " 

N  O  00   2  *•"*    S?'*^  WN  M           '"               Sn"CN\o''ro 

^0         ° 

XXX 
i-o  o   ^1- 

rf  rf  ro 

O    0    0       0 
O   LO  LO     LO 

M                         f) 

[M 

M 

X-f'  --h                !'r       "  -h'  H-                               O    O    O    O    «•> 

-  0    rj- 

i-         ri 

x  y<  x 

8888-8 

" 

«J.-T                       f.   -'T                            10  i^  «   rooo 

y 

XXX 

10  O    O   LO  LO 

3 

r-i  O   -t 

j-                      C-l     fl 

g 

|| 

N^C  \§o        ^,M            •  •  ^     _,.    -j.                            vo  O  OO    ro     • 
iX'^s       -            .  .^"7-7                        C\  i-.  O   r^    • 
H,    ro  0    -    -      .                              ro                          «    M      . 

O  O    -t 

XXX 
«     "    ro 

06          o 

O    O      .       O 

LO   LO       *            O 

fl 

2- 

•</* 

IM 

«  ;  -«Sis  '  -JglB-       -^1^* 

x 

•/'. 
•s.     •   Z 

"S         ti 

1 

1  S    '  fl"  5  8  S  f  o  1       1  1  ?|  S 

T3 

'r 

Isi 

Sff  '.IP  ' 

c:  £        3 

Name  and  number  .  -i 

-'u^^^^li'^-^-Qvi              o'?O'S)P 

"i  i's  II-  5  «-  ?l-s    ^i  1s. 

l4-rf^I-flall:l;l     f&f-  § 

^S^^^^^i^^^        §'£|§§ 

'•      °^^Q.S=0°S'0^               2«  —  -c'R 
v.     V-Q     SoT^'Ci-i-ajXi^           C3^aju 

g^^^-S^-a^S-S^^         S^a^M 
.2    «  l^-g  "3  6  1  1-  2  ^  S     ''       *  '^  £  -s 

lijj||fil|.2^  ilf.^li 

Shipping  measurements  (ou 

C     "O     <-fc-l 

•"^.  C    O 

C    £  -C 

15  -o  c 

III 

XXX 

Prices  : 
Of  drill  complete,  unmou 
Adj'ble  tripod  and  w'ts,  co 
(  )f  column  6  feet  high 
Of  drill  with  tripod  and  w 
or  column,  complete 

*  Plain  tripod. 

TOOLS   AND    MACHINERY    EMPLOYED. 


733 


PRICES   OF  STEAM-DRILLING  TOOLS. 

Steam  drill $185.00  to  $480.00 

Steam  boiler $230.00  to    

Steam  hose .  54  to  97  cents  per  foot 

Drill-steels,  per  set $25.00  to  $115.00 

Blacksmith's  swages  for  dressing  drills.'. $15.00 

Forge  and  hand  tools ..$50.00  upward 

Sand-pumps,  each $3.00 

Giant  blasting-powder,  per  pound . . :   15  to  60  cents 

Leading-wires,  per  foot ,1  cent  upward 

Magneto-electro  blasting  apparatus,  each .$25.00  to  $50.00 

Derricks,  each , $100.00  upward 

PORTABLE  BOILERS  for  operating  steam  drills. — Fig.  218  shows 
a  convenient  arrangement  of  a  steam  boiler  for  operating  rock- 


FIG.  218. — PORTABLE  BOILEB. 


drills.     A  water-tank  occupies  one  end  of  the  frame  and  fuel  can 
be  carried  on  the  other  end.     Price  from  $400  upwards. 


734 


HIGHWAY    CONSTRUCTION. 


1036.  Tools  Employed  in  the  Construction  of  Broken-stone  Roads 
— STONE-HAMMERS. — The  hammers  generally  used  for  breaking 
stone  are  three,  viz. : 

Sledges,  5  pounds  and  over. . . . , . , , .  30  cents  per  pound 

Hand  hammers,  3  to  5  pounds. 36     "       "         " 

l£to  2     ""     45     " 

THE  RING-GAUGE,  for  testing  the  size  of  the  stone  and  through 
which  the  largest  stone  should  in  all  positions  freely  pass.  The 
diameter  is  usually  2£  inches,  can  be  made  by  any  blacksmith  at  a 
cost  of  25  cents. 

THE  STRAIGHT-EDGE,  Fig.  219,  is  used  for  obtaining  the  proper 
transverse  form  of  roads.  It  consists  of  a  horizontal  bar  having  in 
the  centre  of  its  length  a  plummet  for  ascertaining  when  the  straight- 
edge is  level.  Gauges  formed  of  upright  pieces  of  wood  marked  off 
in  inches  are  placed  at  every  four  feet;  these  upright  pieces  have  a 
slot  cut  in  them  so  as  to  allow  of  their  being  moved  either  up  or 
down  and  adjusted  to  the  desired  depths  below  the  horizontal  line. 
These  upright  pieces  are  secured  to  the  straight-edge,  as  shown  in 
the  section,  by  a  small  bolt  passing  through  the  slot  in  the  upright 
and  the  straight-edge,  the  bolt  being  furnished  with  a  thumbscrew, 
by  tightening  which  the  gauges  are  fixed  in  place  when  adjusted  to 
the  required  depths. 


FIG.  219. — STRAIGHT-EDGE. 

LINES. — Linen,  in  rolls  100  feet  long;  price  per  dozen  rolls  $9. 

REEL  AND  STAKE. — Price  per  dozen  16  to  $9.50. 

STONE-FORKS. — The  broken  stone  can  be  more  easily  and 
quickly  taken  up  and  thrown  upon  the  roadway  by  the  use  of  forks 
than  by  shovels.  The  price  of  forks  ranges  from  $18  to  $25  per 
dozen. 


TOOLS   AND    MACHINERY    EMPLOYED. 


735 


FIG.  220. — ROADBED-ROLLER, 

KOADBED-ROLLER,  Fig.  220. — This  is  a  very  efficient  form  of 
roller  for  compacting  embankments  and  the  subgrade  surface  of 
highways.  The  roller  is  5  feet  long  with  nineteen  sections,  ten 


FIG.  221.— SPRINKLING-CART. 


736  HIGHWAY    CONSTRUCTION". 

of  35  inches  in  diameter  and  nine  of  32  inches  in  diameter,  set 
alternately.  The  sections  act  dependency  on  the  axle.  Weight 
about  24-  tons.  Price  $265. 

SPRINKLING-CARTS. — Fig.  221  shows  a  convenient  form  of 
sprinkling-cart  for  use  either  on  construction  or  sprinkling  subur- 
ban streets  and  country  roads.  Capacity  about  150  gallons.  Price 
about  $100. 

BAKES  used  for  spreading  the  stone  should  be  about  twelve 
inches  long  and  have  prongs  from  two  to  three  inches  in  length, 
spaced  three  quarters  of  an  inch  apart,  and  have  handles  about 
six  feet  long.  The  price  of  such  rakes  is  from  $12  to  $15  per 
dozen. 

STONE-CRUSHERS. — The  leading  styles  of  stone-crushers  are 
illustrated  in  Figs.  222  to  232.  The  dimensions,  capacity,  weights, 
etc.,  are  given  in  the  tables  on  pages  631,  G32,  and  633. 

The  amount  of  the  product  in  a  given  time  will  vary  according 
to  the  character  of  the  rock  to  be  broken  as  well  as  to  the  size  to 
which  it  is  broken;  the  smaller  the  size  the  less  the  amount  broken 
and  the  greater  the  power  required. 

In  getting  an  engine  to  drive  a  stone-crusher  it  is  advisable  to 
provide  one  of  greater  power  than  is  stated  in  the  tables,  for  no  close 
estimate  can  be  made  to  cover  all  varieties  of  rock,  and  it  is  more 
economical  to  use  10  H.  P.  from  a  12  or  15  H.  P.  engine  than  from 
a  10  H.  P.  engine. 

For  cost  of  crushing  stone  and  cost  of  operating  crushing- 
plants  see  Art.  365  et  seq.,  and  Table  XXXIX. 

PORTABLE  CRUSHERS. — Any  one  of  the  crushers  described  can  be 
had  in  portable  form.  Some  are  made  portable  by  mounting  on  low- 
wheeled  trucks,  others  by  attaching  travelling-wheels  directly  to  the 
frame  of  the  machine,  and  others  by  attaching  a  pair  of  wheels  to  one 
end  to  act  as  a  front  truck,  using  the  fly-  or  balance-wheels  of  the 
machine  as  rear  travelling-wheels.  When  the  balance-wheels  are  used 
for  this  purpose,  it  is  necessary  to  have  independent  belt-wheels.  If 
the  balance-wheels  are  used  for  belt- wheels,  it  will  be  necessary  to 
have  either  a  metal  or  wood  covering  which  can  be  easily  placed 
and  removed,  for  the  face  of  the  balance-wheels  will  become  too 
roughened  to  be  used  directly  for  belting.  Fig.  233  shows  one  of 
the  many  forms  of  portable  crushers. 


TOOLS   AND   MACHINERY    EMPLOYED. 


BRENNAN  CRUSHER. 


Size  or  Re- 
ceiving 
Capacity 

Approximate 
Product  per 
Hour  in  Tons 
to  Macadam  Size. 

Approximate 
Weight. 

Proper 
Speed. 

Horse-power 
Required. 

Prices. 

5x20 

8  to    10 

7,000 

300 

8 

7x20 

12          15 

10,000 

300 

12  to  15 

8x12 

8          10 

8,000 

280 

8 

8x25 

15          20 

13,000 

280 

15  to  20 

10x25 

20          30 

16,000 

280 

20    "  30 

12x37 

30          40 

32000 

260 

30    "  40 

20x48 

60        100 

72,000 

240 

80 

GATES   CRUSHER. 


2x   4 

4x10 
5x12 
6x14 
7x15 
8x18 
10x20 
11x24 
14x30 
18x42 


500 

3,300 

5,600 

7,800 

13,800 

21,500 

27,000 

40,500 

65,800 

89,000 


2  to      4 


4 
6 

10 
15 
25 
30 
50 
100 


8 

20 

30 

40 

60 

125 

150 


s?        Space  Occupied 
'>       '      by  Breaker. 
g  Inches. 


700 
500 
475 
450 
425 
400 
375 
350 
350 
350 


24 
50 
55 
61 
75 
91 
101 
114 
144 
156 


*1°1 
Sgttl 


13 

28 

46J 
54i 
79| 
88 
103 
120 
132 


1  to 

4 

8 
IS 
80 
85 
80 
40 
75 
100 


g 

10 

15 
25 
30 
40 
60 

125 

150 


$  125 

400 

600 

800 

1200 

1900 

2500 

3500 

6000 

7000 


FORSTER  CRUSHER. 


No. 

Open- 
ing in 
Jaws. 

Speed. 

Horse- 
power. 

Total 
Weight. 

Capacity  per 
Hour  Varies  ac- 
cording to 
Matter  Crushed. 

Floor- 
space 
Required 

Price. 

Cost  Extra 
Sets  Dies, 
per  Set. 

1 

4x   9 

350 

1 

l,8001bs. 

1  to   2  tons 

4ix3f 

$  190 

$10 

2 

5x15 

300 

3 

4,500     " 

4  «<    7    " 

6  x4^ 

390 

25 

3 

7x18 

300 

5 

7,400    »• 

5  "    8    " 

7  x5J 

570 

85 

5 

12  x  24 

250 

8 

17,000    " 

10  "  14    " 

11   x7| 

1000 

90 

738 


HIGH  WAY    CONST  II  U.CT10N. 


FARREL  CRUSHER. 


1 

Size  or  Receiving 
Capacity. 

Approximate  Capacity  in 
Tons,  per  day  of  10  Hours, 
to  Sizes  Stated. 

Extreme 
Dimensions. 

Revolutions  of 
Pulley. 

Horse-power 
Required.  \ 

Total  Weight. 

• 

gj 

"So 
a 

3 

JB 

1 

QQ 

fi 

.££ 
'53 

w 

6* 
8 

*9 
*10 
*11 
*12 
*13 

15  X  9 
16  X  10 
20X10 
24  X  15 
30  X  13 
30  X  15 
36X20 
36X24 

tons.      in. 
100  to  2* 

120        2£ 
175        3 
250        3 
300        3 
400        4* 
800  •'    8 
1000  "  10 

tons.   in. 
80  to  2 
100       2 
150       2j- 
200       2* 
•<275       2£ 
350       3* 
600       6 
800       8 

tons.  in. 
55  to  1J 
75  »  H 
125  "  2 
175  "  2 
225  "  2 

500  to  5" 

ft.  in. 
7      0 
7      2 
7      8 
7    10 
8      6 
8      6 
9    10 
9    10 

ft.  in. 
5      3 

5      6 
5    10 

7      2 
8      2 

8      2 

8      8 
8      8 

ft.  in. 
5      3 
5      3 
5      1 
5      9 
6      4 
6      4 
6    10 
6    10 

275 
275 
275 
275 
275 
275 
275 
275 

12 

15 
20 
25 
30 
30 
40 
40 

Ibs. 
15,000 
16,200 
18,300 
26.000 
37,600 
37«00 
50,000 
50,000 

$  750 
375 
1050 
1575 
2250 
2250 
2875 
2875 

*  These  sizes  have  two  driving-pulleys. 


CHAMPION  CRUSHER. 


No. 

Size  or  Receiv- 
ing Capacity 
of  Jaws. 

Product  per 
Hour  in  Tons 
when  Machine 
is  Closed  to 
2  Inches. 

Weight, 
Approxi- 
mated. 

Speed, 
Revo- 
lutions. 

Driving- 
pulleys, 
Diameter 
and  Face. 

Horse- 
power 
Required. 

Price. 

inches. 

tons. 

Ibs. 

inches. 

3 

7  X  13 

7  to  13 

5,000 

180 

44  X     8 

12 

$  600 

4 

9  X  15 

12  "  18 

8,000 

160 

50  X    8 

15 

800 

5 

11  X  26 

24  "  36 

16,000- 

150 

60  X  10 

25 

1500 

CLIMAX  CRUSHER. 


No.  1. 

No.  2. 

No.  3. 

No.  4. 

Size  of  top  opening  of  jaws  in  inches  
Product  per  hour  in  tons  when  machine 
closes  to  2  inches  

7X  13 
7  to  12 

9X16 
10  to  15 

10*X22 
15  to  30 

12  X  28 
25  to  40 

Weight,  approximate  .  . 

5  000 

8  500 

15  000 

20,000 

Weight,  with  two-wheeled  trucks  and  ele- 
vator          .  . 

6  000 

10  000 

Weight,  mounted  on  4  wheels,  with  10-feet 
elevator  

7  200 

11  000 

Speed,  revolutions  

325 

300 

290 

275 

Driving  pulleys,  diameter  and  face,  inches 
Horse-  power  required  ....                 

28X8 
10 

32  X  9 
12 

38  X  10 
25 

42  X  12 
35 

Floor-space  required  length 

5ft 

6ft. 

7ft. 

8  ft.  1  in. 

Floor-space  required,  width  

4  ft  4  in. 

5  ft.    1  in. 

5  ft.  6  in. 

6ft, 

Extreme  height  of  machine 

2ft  7  in. 

3  ft.  10  in. 

4  ft.  7  in. 

4  ft.  10  in. 

No.  1 

No.  2 

No.  3 

No.  3 

Diameter  of  screen  best  suited,  in  inches  .  . 

30 

30 

36 

36 

TOOLS   AND    MACHINERY    EMPLOYED. 


WESTERN  CRUSHER. 


No. 

Size  or  Receiv- 
ing Capacity 
of  Jaws. 

Product 
per  Hour. 

Weight, 
Approxi- 
mated. 

Speed. 
Revo- 
lutions. 

Diameter  and 
Face  of  Driv- 
ing-pulleys. 

Horse-power 
Required. 

inches. 

tons. 

Ibs. 

inches. 

5 

7  X  13 

10  to  12 

5,000 

200 

40  X    6£ 

8  to  10 

10 

9X  151 

12  "  20 

8,000 

200 

44  X     8 

10  "  12 

15 

10  X  22 

18  "  25 

14,000 

200 

44  X  10* 

15  "  20 

AUSTIN  CRUSHER. 


1 

Jaw-opening 
in  Inches. 

Size  Engine 
Required. 

Speed.  Revols. 

Weight  of 
Crusher. 

y 

>> 

Floor-opace 
Required. 

Price.  Not 
Mounted. 

Price.  Mounted 
on  Four-wheel 
Trucks. 

Price  of  Extra 
Dies.  Per  Pair. 

3 

8X  15 

10  H.  P. 

300 

6000  Ibs. 

10  to  14 

2*  X  7  ft. 

$600.00 

$  725.00 

$40.  00 

4 

10  X  18 

15      " 

300 

8000    " 

15  "  20 

3X8" 

900.00 

1050.00 

50.00 

Elevator,  14  ft.  long,  $175;  for  each  additional  foot  add  $5.  Revolving  screen,  2-section, 
$200;  3- section,  $250.  Each  section  is  2±  ft.  long  by  2  ft.  in  diameter,  made  of  steel,  and 
turns  on  anti-friction  rollers. 


BLAKE   CRUSHER. 


Size  or  Receiv- 
ing Capacity. 

Product  per  Hour 
in  Cubic  Yards. 

Weight  of 
Heaviest 
Piece. 

Total  Weight. 

Extreme  Dimensions. 

1§ 

Horse-power 
Required. 

Price,  f.o.b. 
Pittsburg, 

! 
1 

*j 

« 

1 

Proper  Sp 
Revolut 

inches. 
10  X  4 
10  X  7 
15  X  9 
20  X  12 
20  X  15 
24  X  18 

3 
5 
'  7 
10-12 
j     Coarse  or  Pre-     ) 
1  liminary  Breaker,  f 

Ibs. 
1,695 
4,339 
6,500 
10,000 
8,450 
9,425 

Ibs. 
4,000 
8,000 
15,000 
21,000 
32,600 
37,500 

ft.    in. 
3      11 
5        8* 
6        5 
7       0 
8       6 
9      10 

ft.  in. 
3    3 
3    8 
5    0 
5    6 
5    0 
5    1 

ft.  in. 
3  9 
4  5 
5  11 
6  3 
6  7 
6  10 

250 
250 
250 
250 
150 
125 

4 
6 
9 
15 
12 
12 

$275 
450 
750 
1000 

740 


HIGHWAY    CONSTRUCTION. 


FIG.  222. — THE  BEEN  NAN  CRUSHER.    EXTERIOR  VIEW. 


FIG.  223.—THE  BRENNAN  CRUSHER     SECTIONAL  VIEW. 


TOOLS  1ND  MACHINERY  EMPLOYED. 


741 


FIG.  224. — THE  GATES  CRUSHER.    EXTERIOR  VIEW. 


FIG.  225.— THE  GATES  CRUSHER.    SECTIONAL  VIEW, 


HIGHWAY   CONSTRUCTION. 


FIG.  226.— THE  FARREL  CRUSHER.    SECTIONAL  VIEW 


FIG.  227. — THE  CHAMPION  CRUSHER.    SECTIONAL  VIEW. 


TOOLS   AND   MACHINERY   EMPLOYED. 


743 


FIG.  228. —  CLIMAX  CRUSHES.    SECTIONAL  VIEW. 


FIG.  229. — THE  WESTERN  CIIUSHEII.     SECTIONAL  VIEW. 


744 


HIGHWAY   CONSTKUCTION. 


tor 


FIG.  230.  — THE  AUSTIN  CRUSHER.     SECTIONAL  VIEW. 


FIG.  231 —THE  BLAKE  CRUSHER.     SECTIONAL  YIEW. 

SCKEEXS. — Nearly  all  specifications  for  broken  stone  call  for  it  to- 
be  screened,  either  to  separate  it  into  different  sizes  or  to  remove 
the  tailings;  for  either  purpose  revolving  screens  made  of  steel 
plate  perforated  with  holes  of  the  required  size  are  employed.  They 
can  be  run  in  several  ways,  as  shown  in  Figs.  237  to  241. 


TOOLS   AND   MACHINERY    EMPLOYED. 


745 


FIG.  232.— THE  FORSTER  CRUSHER.    SECTIONAL  VIEW. 


FIG.  233.— GATES  PORTABLE  CRUSHER. 


746 


HIGHWAY    CONSTKUCTTOiSr. 


Fig.  234  shows  a  three-section  screen;  the  first  section  has  holes 
one  inch  in  diameter,  the  second  section  holes  one  and  one  half 
inches  in  diameter,  and  the  third  section  holes  two  and  one  half 
inches  in  diameter.  Holes  of  any  other  dimensions  may  be  used, 
depending  upon  the  sizes  desired.  Dust-jackets  are  also  used  in 
connection  with  the  screens,  thus  separating  the  dust  from  the 
crushed  stone.  The  following  table  contains  the  usual  dimensions, 
weight,  price,  etc.,  of  steel-plate  screens: 


No. 

Diam- 
eter. 

Length, 
with  three 
sections. 

Revolu- 
tions of 
Pulley. 

Size  Pulley, 
Diameter 
Face. 

Weight, 
Lbs. 

Price  for 
three  sections 
complete. 

Price  for 
two  sections 
complete. 

inches. 

ft.      in. 

inches. 

1 

24 

10     6 

90 

30  X  6* 

2200 

$275 

$225 

2 

30 

12     6 

90 

36X  8 

3550 

385 

325 

3 

36 

12    6 

80 

36X  8 

3900 

450 

375 

4 

43 

12     6 

70 

36  X  8J 

4500 

550 

450 

5 

.    48 

15     6 

60 

42x  9 

5500 

700 

575 

6 

54 

15     6 

60 

48x10 

950 

800 

FIG.  234.— REVOLVING  STONE- 


TOOLS   AND    MACHINERY    EMPLOYED. 


'47 


FIG.  235. — SEMI-PORTABLE  ENGINE  AND  BOILER. 


AND  BOILERS  FOR  DRIVING  ROCK-CRUSHERS  are 
usually  of  the  portable  or  semi-portable  type.  Fig.  235  shows  a 
compact  combination  of  the  semi-portable  form,  and  Fig.  236  shows 
the  portable  type. 


'48 


HIGHWAY    CONSTRUCTION. 


FIG.  236.— PORTABLE  BOILER  AND  ENGINE. 

SPECIFICATIONS   OF  PORTABLE  BOILERS   AND  ENGINES   ON 
WHEELS.     FIG.  236. 


1 

No.  of  size  .  

0 

1 

2 

3 

4 

5 

6 

b 

g 

Horse-power  

6 

8 

10 

1-2 

15 

20 

25 

30 

35 

Diam.  of  cylinder,  in 

5 

5 

6 

7 

8 

8 

9 

10 

10 

Length  of  stroke,  in. 

8 

8 

9 

10 

10 

12 

12 

12 

15 

Usual  no.  revolutions 

185 

240 

190 

160 

160 

170 

170 

170 

150 

Diam.  of  pulleys,  in. 

14&32 

14&32 

1G&36 

20&44 

20&44 

30&48 

3-J&54 

3C&54 

36&60 

Face  of  pulleys,  in... 
Diam.  of  boiler,  in.  .  . 

8t|81 

8»*6, 

8*&9^ 
30 

10i&10i 
32 

10J&10J 
32 

8J&12J 
34 

10£&12£ 
36 

10£&12i 
36 

10i&14.i 
40 

Length  of  furnace,  in 
Height  of  furnace,  in 

84 

30 

36 
32 

38 
31 

38 
38 

44 
38 

52 

33 

52 
40 

52 

40 

52 
44 

Width  of  furnace,  in. 

21 

22 

£4 

26 

26 

28 

30 

30 

34 

No.  of  3-inch  tubes... 

17 

20 

22 

26 

26 

80 

34 

34 

40 

Length  of  tubes,  in.. 

54 

66 

72 

72 

78 

90 

96 

102 

102 

Shipping  wt.complete 
Price 

4800 
$700 

5000 

$724 

5700 

$788 

6000 

$880 

7100 
$931 

8100 
$1045 

9500 

$1085 

10,500 
Si,  277 

11.300' 

$1,551 

STONE-CRUSHING  PLANTS. — Complete  crushing-plants  include 
a  stone-crusher,  engine,  boiler,  shafting,  pulleys,  and  belting.  These 
plants  maybe  divided  into  two  classes,  viz.,  stationary  and  portable. 
In  arranging  either  class  of  plant  care  must  be  taken  to  save  un- 
necessary handling  of  the  stone;  to  this  end  the  crusher  must  be 


TOOLS   A2STD   MACHINERY    EMPLOYED. 


749 


placed  (1)  so  as  to  receive  the  stone  directly  from  the  carts  or  other 
conveyance  used  to  transport  it  from  the  quarry,  and  (2)  so  as  to 
deliver  the  broken  stone  into  the  vehicles  which  are  to  haul  it  away 
without  handling. 


FIG.  387.— CRUSHING-PLANT  FOR,  HILLSIDE  LOCATION. 


FIG.  238. — CRUSHING-PLANT  FOR  LEVEL  GROUND. 

In  Figs.  237  to  240  a  few  illustrations  are  presented  showing 
simple  methods  of  arranging  plants.  Fig.  237  shows  a  fixed  plant 
for  hillside  location,  with  road  graded  for  delivery  of  stone  to  the 
crusher,  and  chute  for  delivery  of  broken  stone  to  the  carts. 

Fig.  238  shows  a  fixed  plant  for  location  on  level  ground,  with 
road  graded  for  delivery  of  stone  to  crusher,  and  elevator  for  rais- 
ing crushed  stone  to  chute  for  delivery  into  carts. 


•50 


HIGHWAY    CONSTRUCTION. 


Fig.  239  shows  a  plant  for  temporary  use,  with  platform  for  re- 
ceiving the  stone  to  be  crushed,  three-section  screen,  and  platform 


FIG.  239. — TEMPORARY  CRUSHING-PLANT. 


FIG.  340. — PORTABLE  CRDSHLNG-PLANT. 

for  receiving  the  crushed  and  screened  stone,  from  which  it  can  be 
shovelled  into  the  carts  or  an  elevator  can  be  attached. 

ig.  240  shows  a  portable  plant  with  elevator  and  screen. 


TOOLS   AND    MACHINERY    EMPLOYED. 


Fig.  241  shows  a  portable  plant  with  crusher  elevated  sufficiently 
to  allow  of  a  screen  being  used  without  the  employment  of  an  ele- 
vator. 


SIW- 

FIG.  241. — CRUSHER  MOUNTED  ON  WHEELS. 

STONE-DISTRIBUTING  CARTS.— The  cart  shown  in  Fig.  242  is 
specially  designed  for  distributing  broken  stone  for  building  or  re- 
pairing roads.  The  cart  is  mounted  on  four  wheels,  so  arranged 
that  it  can  be  turned  in  a  short  space.  The  bottom  of  the  carfc 
slopes  downward  to  the  back,  and  the  tail-board  is  hinged  at  its 
upper  edge  and  is  furnished  with  two  adjusting  chains  by  which 
the  opening  or  swing  of  the  lower  edge  is  regulated.  Steel  wings  are 
attached  to  the  sides  of  the  cart  at  the  tail-board  for  the  purpose  of 
spreading  the  stone  the  full  width  between  the  wheels.  The  cart 
is  tilted  by  a  rack  and  pinion  operated  by  the  driver,  and  may  be 
fixed  at  any  desired  angle.  As  the  stone  flows  from  the  rear  of  the 
cart  it  is  levelled  by  a  scraper  attached  to  the  bottom  of  the  tail- 
board; this  scraper  is  pivoted  at  the  centre  and  can  be  adjusted  so 
as  to  spread  the  stone  to  any  required  thickness  and  over  any  de- 
sired width  equal  to  or  less  than  the  gauge  of  the  cart,  and  thicker 
on  one  side  than  on  the  other. 

The  carts  are  built  in  two  sizes,  to  be  hauled  by  two  or  three 
horses,  respectively,  the  horses  oeing  harnessed  abreast.     The  two- 


752 


HIGHWAY   CONSTRUCTION. 


horse  size  is  five  feet  wide  and  has  a  capacity  of  one  and  one  half 
cubic  yards,  and  weighs  empty  2250  pounds.  The  three-horse  size 
js  seven  feet  six  inches  wide  and  has  a  capacity  of  two  and  one  half 
cubic  yards,  and  weighs  empty  2750  pounds. 

The  price  of  the  two-horse  cart  is  $175,  and  of  the  three-horse 
size  $200. 


FIG.  242. — STONE-DISTRIBUTING  CART. 

HOUSE  EOLLERS. — The  following  figures  show  a  few  selections' 
from  the  large  variety  of  horse  rollers  in  the  market.  The  principal 
dimensions,  weights,  and  prices  are  given  on  pages  647  and  648. 


FIG.  243.— ENTERPRISE  ROLLER. 


For  the  advantages  of  rolling,  form  of  rollers,  amount  of  rolling, 
etc.,  see  Articles  396,  397,  and  400. 


TOOLS    AND    MACHINERY    EMPLOYED. 


753- 


THE  ENTERPRISE  EOLLER,  Fig.  243. — This  roller  is  made  in  two 
forms,  "  reversible  "  and  "  non-reversible."  Both  styles  are  made 
in  sizes  of  3,  4,  5,  and  6  tons,  the  diameter  of  the  rolling  cylinders; 
being  respectively  54,  56,  58,  and  60  inches,  and  a  width  of  54 
inches,  which  is  common  to  all  weights.  The  non-reversible  roller 
is  equipped  with  a  ballast-box  which  will  hold  a  weight  of  2  tons, 
so  that  a  4-ton  roller  can  be  increased  to  6,  and  a  6-ton  to  8  tons. 
Price  about  $100  per  ton.. 

Pope's  reversible  roller,  Fig.  244,  is  made  in  sizes  ranging  from 
5  to  10  tons.  The  diameter  of  the  5-ton  roller  is  5  feet,  and  width 


FIG.  244. — POPE'S  REVERSIBLE  ROLLER. 


5  feet.     The  diameter  of  the  10-ton  roller  is  7£  feet,  and  width 
5  feet.     Price  $100  per  ton. 

The  Champion  reversible  roller,  Fig  245,  is  constructed  in  two 
sections  which  revolve  independently  on  the  axle.  The  diameter 
of  the  rolls  and  width  of  the  rolling  face  are  the  same,  viz.,  5 
feet.  This  roller  is  made  in  four  weights,  viz.,  2£,  3£,  4J,  and  5£ 
tons,  and  each  is  supplied  with  two  steel  boxes,  each  of  which  will 
hold  about  a  ton  of  pig  iron,  thus  converting  each  roller  from  a 
light-  to  a  medium-  or  heavy-weight  roller,  as  desired.  Price  £J 
tons  $350;  for  each  additional  ton  add  $50. 


754  HIGHWAY   CONSTRUCTION". 

The  Austin  roller,  Fig  246,  is  made  in  weights  of  3  J,  4,  and  4J 
tons.     The  rolls  are  4£  feet  in  diameter,  and  width  5  feet. 


FIG.  245.— CHAMPION  REVERSIBLE  ROLLER. 


FIG.  246. — AUSTIN  REVERSIBLE  ROLLER. 

STEAM  ROLLERS. — There  is  a  large  variety  of  steam  rollers  in 
the  market  from  which  to  select.  The  leading  types  are  shown  in 
Figs.  247  to  151,  and  the  principal  dimensions,  etc.,  are  given  in 
the  following  tables. 

For  the  advantages  of  rolling,  cost  of  maintaining  steam  rollers, 
and  amount  of  rolling  required,  etc.,  see  Articles  396,  398,  403,  and 
404. 


TOOLS   AND   MACHINERY   EMPLOYED. 


755 


THE  SPRINGFIELD  ROLLER.      FIG.  247. 


25,000  Ibs. 

30,000  Ibs. 

35,000  Ibs. 

48  inches 

48  inches 

48  inches 

40  inches 

44  inches 

48  inches 

Beveled  driving-wheels,  diameter  .  .  . 

76  inches 
20  inches 

76  inches 
22  inches 

76  inches 
24  inches 

Extreme  width,  of  machine          •    • 

70  inches 

78  inches 

86  inches 

{Jompression  per  souai'6  inch  

550  pounds 

6(JO  pounds 

650  pounds 

'Ooal  capacity        ••  

450  pounds 

500  pounds 

550  pounds 

280  gallons 

315  gallons 

350  gallons 

Maximum  grade  ascended  with  120 
pounds  steam  on  loose  metalling.  .  . 

22  per  cent. 

22  per  cent. 

22  per  cent. 

THE  PITTS  ROLLER.      FIG.  248. 


10-ton. 

12^-ton. 

15-ton. 

Front  roll,  diameter  
Front  roll    width 

44  inches 
47  inches 

46  inches 
51  inches 

48  inches 
52^  inches 

Driving-wheels,  diameter.  . 
Driving-wheels,  width  
Extreme  width  of  machine 
\Vheels  base        •  •  •  •  

69  inches 
18  inches 
78  inches 
117  inches 

69  inches 
20  inches 
89  inches 
128  inches 

72  inches 
22  inches 
94  inches 
133  inches 

400  pounds 

500  pounds 

500  pounds 

^Vater  capacity 

225  gallons 

275  gallons 

320  gallons 

Coal  consumption   per  dny 
varies  according  to  work 
and  grades  from 

400  to  900  Ibs. 

600  to  1000  Ibs. 

800  to  1200  Ibs. 

Travelling  speed  per   hour 
with  fast  gear  

2.92  miles  per  hour 

2|  to  2f  miles 

2|  miles 

Travelling  speed  per   hour 
with  slow  gear              .  .  . 

2.21  miles  per  hour 

2  miles 

1.85  miles 

THE  HARRISBURG  ROLLER.    FIG.  249. 


10-ton. 

12-  ton. 

15-ton. 

Driving-wheels  width  

18  inches 

20  inches 

22  inches 

Pressure  per  inch  of  width  

466  pounds 
400  pounds 

500  pounds 
500  pounds 

566  pounds 
600  pounds 

Water  capacity  

130  gallons 

155  gallons 

180  gallons 

Maximum  grade  ascended  with 

20  per  ct. 

20  per  ct. 

20  per  ct. 

HIGHWAY    CONSTRUCTION. 


THE  AVELING  &  PORTER  ROLLER.     FIG.  250. 

10-ton. 

15-ton. 

20-ton. 

45  inches 
66  inches 
78  inches 
450  pounds 
approx. 
400  pounds 
150  gallons 

17  per  ct. 

48  inches 
72  inches 
87  inches 
550  pounds 
approx. 
450  pounds 
200  gallons 

17  per  ct. 

54  inches 
78  inches 
96  inches 
650  pounds 
approx. 
500  pounds 
250  gallons. 

17  per  ct. 

Driviuff-wheels   diameter        . 

Extreme  width  of  machine  
Pressure  per  inch  of  width  

Coal  capacity            

^Vater  capacity  

Maximum  grade  ascended  with 
100  pounds  of  steam  on  bin  ol 

THE  COLUMBIAN  ROLLER.   FIG.  251. 

27,000  Ibs. 

32,500  Ibs. 

38,000  Ibs. 

Front  roll    diameter  

48  inches 
70  inches 
20  inches 
81  inches 

sufficient 

507  pounds 
14  to  20 

48  inches 
72  inches 
22  inches 
87  inches 

for  5 

575  pounds 
feet  per 

52  inches 
74  inches 
24  inches 
95  inches 

hours 

6d5  pounds 
100 

Drivincr  wheels   diameter  .  .    . 

Driving-wheels   width       

Extreme  width  of  machine  
Coal  capacity    \ 

Water  capacity  f  '  ' 
Compression     of    drivers     per 

THE  RUSSELL  ROLLER.    FIG.  247a. 


10-  ton. 

12i-ton. 

15-ton. 

Front  rolls,  diameter  

50  inches 

52  inches 

54  inches 

Front  rolls,  width  

46  inches 

48  inches 

50  inches 

Driving-wheels,  diameter  
Driving-wheels  width 

70  inches 
20  inches 

72  inches 
22  inches 

74  inches 
24  inches 

Extreme  width  of  machine..  .  . 
Coal  capacity  

73  inches 
450  pounds 

79  inches 
500  pounds 

87  inches 
600  pounds 

285  gallons 

365  gallons 

415  gallons 

TOOLS   AND    MACHINERY   EMPLOYED.  757 


FIG,  247. — THE  SPRINGFIELD. 


FIG.  247 a.—  THE  RUSSELL  ROLLER. 


758  HIGHWAY    CONSTRUCTION. 

SCARIFIERS. — This  is  the  name  given  to  the  tools  or  mechanical 
devices  used  for  picking  or  breaking  up  of  broken-stone  roads  pre- 
paratory to  the  applying  of  new  metal.  In  England  these  tools- 
are  extensively  employed.  There  are,  broadly  speaking,  two  types, 
the  one  fashioned  on  the  form  of  ploughs  and  harrows,  and  the 
other  based  on  the  principle  of  the  rock-drill  and  ore-stamping 
mill.  Each  type  is  arranged  to  be  operated  by  attaching  to  the 
steam-roller  or  by  a  traction  engine,  and  is  provided  with  regu- 
lating devices  which  adjust  the  depth  of  penetration.  It  is  con- 
sidered that  a  suitably  constructed  scarifier  will  perform  the  work 
more  expeditiously  and  thoroughly  than  it  can  be  performed  by 
hand,  and  at  one-half  the  cost. 

Steam-rollers  are  usually  furnished  with  spikes  to  fit  in  sockets 
on  the  hind  rollers,  which  are  intended  to  be  used  for  breaking  up 
roads,  but  they  do  not  usually  perform  this  operation  in  a  satis- 
factory manner. 

The  scarifiers  employed  in  the  United  States  are  generally  of 
the  plough  type,  and  are  drawn  by  four  to  eight  horses.  The  shoe 
is  usually  reversible  and  adjustable,  and  provided  with  a  sharp  and 
a  blunt  point.  It  is  found  that  in  some  work  the  sharp  point  is  the 
better;  in  other  work  the  blunt  one  is  more  suitable. 

When  using  scarifiers  it  is  essential  to  have  the  road  thoroughly 
soaked  with  water. 


TOOLS   AXD    MACIIIXERY    EMPLOYED. 


759 


FIG.  248— THE  PITTS. 


249.— THE  HARRISBUBG. 


760 


HIGHWAY   CONSTRUCTION. 


.  250.— THE  AVJLLING  &  POKTBR. 


FIG.  251.— THE  COLUMBIAN. 


TOOLS   AND   MACHINERY    EMPLOYED. 


761 


1037.  The  Tools  employed  for  the  Maintenance  of  Broken-stone 
JEloads  are : 

Shovels. , per  dozen  $  7.00  to  $13.50 

Picks "     ,"  10.75  "  "22.50 

Spades "       "  13.25  "     14.50 

Hoes •'      "  13.50 

Rakes...,. "       «  14.00  to    16.00 

Hand  rammers each  1.15"     12.00 

Wheelbarrows per  dozen  20.00  "     52.50 

Brush-hooks.... "       "  17.00 

Axes "       "  12.00  to     15.50 

Scrapers '. each  8.00"     12.00 

Brooms — per  dozen  8.50"       9.00 

Stone-sledges per  pound  .30 

Stone-hammers "         "  .45  to       .30 

Grass-shears each  1.63"       2.63 

Ttirfiug-axes "  1.75 

Sod-lifters "  2.75 

Straight-edges "  12.00 

Drain-cleaners per  dozen  9.00  to    11.00 

Levels "       "  48.00 

Lines "       "  9.00 

1038.  Tools  Employed  in  the  Construction  of  Block  Pavements— 
HAND  HAMMERS. — Cobblestone-hammer,  Fig.  252,  price  $2.50  each. 

Square-block  hammer,  Fig.  253,  price  each  $2.50. 
Brick-hammer,  Fig.  254,  price  each  $1.50. 


FIG.  252. 


FIG.  253. 


FIG.  254. 


Pavers'  crowbars,  per  pound  12  cents. 

Sand-screens,  from  $6  to  $12  each. 

Brooms,  rattan  and  wire,  $4  to  $8  per  dozen. 

HAND  RAMMERS. — Hand  rammers  are  of  different  forms,  as 
ehown  in  Figs.  255  to  259. 

Fig.  255,  used  for  cobblestones,  is  of  wood,  generally  locust, 
banded  with  iron,  weighs  about  40  Ibs.;  price  $4  to  $7.50. 


762 


HIGHWAY    CONSTRUCTION". 


Tig.  256,  used  for  Belgian  blocks,  is  of  wood  and  steel,  weighs 
about  45  Ibs. ;  price  $9. 

Fig.  257,  used  for  granite  blocks,  is  made  of  iron,  with  cast- 
steel  face,  locust  plug,  and  hickory  handles,  weighs  from  45  to  55 
Ibs. ;  price  $9  to  $12. 


FIG.  255. 


FIG.  256. 


FIG.  257. 


FIG.  258.        FIG.  259. 


Fig.  258,  used  for  brick,  is  made  of  wood,  shod  with  cast  iron  or 
steel,  weighs  about  27  Ibs.;  price  $3. 

Fig.  259  is  used  for  miscellaneous  work,  as  tamping  in  trenches- 
and  next  to  curbs,  weighs  about  20  Ibs.;  price  $1.15. to  $3. 

1039.  Tools  Employed  for  Asphalt  Pavements. — The  tools  used 
in  laying  asphalt  pavements  comprise  iron  rakes,  hand  rammers  and 


FIG.  260.— ASPHALT-HAMMERS. 


FIG.  261.— SMOOTHING-IRON. 


TOOLS   AND    MACHINERY    EMPLOYED. 


'63 


smoothing-irons,  hand  rollers,  either  with  or  without  a  fire-pot,  and 
steam  rollers,  either  with  or  without  provision  for  heating  the  front 
roll. 

The  tainping-  and  smoothing-irons  are  shown  in  Figs.  260  and 
261.  They  are  of  cast  iron,  with  wood  handles.  They  are  used 
hot,  being  heated  in  the  portable  fire-box  shown  in  Fig.  263.  They 
cost  about  $20  per  dozen. 


FIG.  262. — FIRE-POT  ROLLER. 


FIG.  263.— PORTABLE  FIRE-BOX. 

Fig.  262  shows  a  hand  roller,  with  fire-pot;  it  is  of  cast  iron,  with 
a  smooth-turned  face,  usually  3  feet  in  diameter  and  3  feet  wide. 
The  weight  varies  from  400  to  1000  Ibs.,  and  the  price  is  about  10 
cents  per  pound. 

The  steam  rollers  used  for  compressing  and  smoothing  asphalt 
and  plastic  pavements  are  different  in  construction,  appearance 


HIGHWAY    CONSTRUCTION. 


and  weight   from  those   employed   for  compacting  broken  stone. 
The  difference  is  due  to  the  different  character  of  the  work  re- 


FJG.  264. — ASPHALT-HOLLER. 


265.  —  ASPHALT-ROLLER. 


quired:  In  compacting  broken  stone  the  solidification  is  mechan- 
ical and  is  effected  by  the  weight  or  pressure  of  the  machine  >  in 


TOOLS   AND    MACHINERY    EMPLOYED. 


765 


the  case  of  ''asphalt  and  plastic  pavements  the  solidification  is 
effected  by  chemical  action,  the  roller  being  only  required  to  bring 
the  constituents  into  more  intimate  contact  and  to  produce  a 
smooth  surface. 

Figs.  264  and  265  illustrate  the  form  of  roller  used  for 
asphalt  and  plastic  pavements;  the  weight  is  usually  five  tons,  but 
they  are  made  in  sizes  ranging  from  three  to  fifteen  tons;  the  rear 
drum  or  roller  is  usually  made  with  solid  heads,  so  that  it  can  be 
filled  with  water  or  sand  and  thus  increase  its  weight. 

There  are  several  of  these  rollers  on  the  market  to  select  from; 
they  all  agree  in  the  principle  of  construction,  differing  only  in 
minor  details  and  dimensions. 


FIG.  266. — ASPHALT-MIXING  MACHINE. 

The  principal  dimensions  of  a  five-ton  roller  are  as  follows  : 

Front  roll  or  steering-wheel 30  to  32  inches  diameter 

Rear  roll  or  driving-wheel 48 

Width  of  front  roll 40       " 

<•      "  rear      ••  40      " 

Extreme  length 14  feet 

height  ....: 7  to  8  feet 

Water  capacity 80  to  100  gallons 

Coal          "       200pounds 

The  price  for  a  five-ton  roller  and  heavier  is  about  $400  per  ton. 


766  HIGHWAY    CONSTRUCTION. 

ASPHALT-MIXERS. — The  general  form  of  the  machines  employed 
for  mixing  the  materials  for  asphaltic  cement  pavements  is  shown 
in  Fig.  266.  The  cut  shows  an  engine  attached  to  the  machine, 
but  this  can  be  omitted  and  the  power  applied  by  belting,  using 
either  spur  or  bevel  gearing  to  suit  location. 

The  machines  are  made  in  various  lengths  and  diameters  and 
with  and  without  steam-jackets. 

A  steam-jacketed  mixer  30  inches  diameter  and  8  feet  long, 
with  a  capacity  of  about  5  cubic  yards  per  hour,  costs  about  $325. 

SURFACE-HEATER  FOR  KEPAIRING  ASPHALT  PAVEMENTS. — 
Fig.  267  shows  the  Perkins  surface-heater  for  repairing  asphalt 
and  mastic  pavements.  It  consists  of  a  metal  tank  mounted  on 
wheels,  and  at  the  rear  of  this  a  series  of  burners  surrounded  by  a 
wire  netting  packed  with  asbestos  cement.  The  tank,  which  has  a 
capacity  of  about  half  a  barrel,  contains  gasoline.  An  air-pump  at 


m 


FIG.  267.— SURFACE-HEATER. 


the  head  of  the  tank  is  used  to  force  the  gasoline  to  the  burners. 
The  purpose  of  the  asbestos  packing  is  to  conserve  and  diffuse  the 
heat.  Each  burner  can  be  turned  on  and  off  at  will,  and  when  all 
are  in  use  the  tank  will  keep  them  running  "for  about  five  hours. 
The  machine  complete  weighs  about  700  pounds. 

The  method  of  operation  is  to  place  the  heater  over  the  space 
to  be  repaired  and  turn  on  the  heat.     In  a  very  short   time  the 


TOOLS   AND    MACHINERY    EMPLOYED. 


entire  surface  of  the  pavement  under  the  hood  is  softened,  so  that 
the  top  can  be  removed  with  a  hoe.  Only  sufficient  of  the  old 
material  is  taken  off  to  secure  a  clean,  fresh  surface,  which,  being 
hot,  the  new  material  welds  perfectly  with  it. 

CONCRETE-MIXING  MACHINES. — Where  large  quantities  of  con- 
crete are  required,  as  in  the  foundations  of  improved  pavements,  con- 
crete can  be  prepared  more  expeditiously  and  economically  by  the  use 
of  mechanical  mixers  and  the  ingredients  will  be  more  thoroughly 
mixed  than  by  hand.  Thorough  incorporation  of  the  ingredients 
is  an  essential  element  in  the  quality  of  a  concrete;  when  mixed  by 
hand,  the  incorporation  is  rarely  complete,  because  it  depends  upon 
the  proper  manipulation  of  the  hoe  and  shovel.  The  manipulation, 
although  extremely  simple,  is  rarely  properly  performed  by  the  or- 
dinary laborer  unless  constantly  watched  by  the  overseer.  Several 
varieties  of  concrete-mixing  machines  are  in  the  market.  A  con- 


FIG.  268.— CONCRETE-MIXING  MACHINE. 


Tenient   portable   type  is  illustrated  in  Figs.  268  and  269.     The 
capacity  of  the  mixers  ranges  from  five  to  twenty  cubic  yards  per 


70S 


HIGHWAY    CONSTRUCTION. 


hour,  depending  upon  size,  regularity  with  which  the  materials  are 
supplied,  speed,  etc.  In  price  they  range  for  machines  without 
engines  from  $425  to  $600  ;  with  engines,  from  $950  to  $1250. 

For  the  advantages  of  concrete,  cost,  etc.,  see  Articles  457  et 
seq. 


FIG.  269. — CONCRETE-MIXING  MACHINE. 


SAND-DRYERS. — Revolving  cylinders  connected  to  a  furnace 
are  employed  for  drying  the  sand  used,  for  the  cushion  coat  of 
block  pavements,  for  mixing  with  asphaltic  cement,  and  for  heat- 
ing the  gravel  used  to  fill  the  joints  in  block  pavements.  They  are 
made  in  various  forms  and  sizes;  the  one  shown  in  Fig.  270  is  15 
feet  long  and  3  feet  in  diameter  and  has  a  capacity  of  5  cubic 
yards  per  hour.  Price  $600. 

Revolving  cylinders  mounted  on  wheels,  9  feet  long  and  2  feet 
in  diameter,  cost  about  $250. 

Rectangular  dryers  mounted  on  wheels,  9  feet  long,  4  feet  wide, 
and  4  feet  deep,  cost  about  $150. 

Pans  6  feet  long,  5  feet  wide,  and  6  inches  deep  cost  about  $20, 


TOOLS   AND   MACHINERY    EMPLOYED. 


'69 


.  370.— SAITD-DRYER. 


FIG.  271. — PORTABLE  HEATER  FOR  ASPHALT  OR  PAVING-CEMENT. 


HIGHWAY    CONSTRUCTION". 


HEATING-KETTLES  are  employed  for  heating  the  paving-cement 
used  for  filling  the  joints  in  block  pavements,  and  for  heating  the 
asphalt  paving  mixture  for  asphalt  pavements  when  it  has  to  be 
conveyed  long  distances  from  the  factory.  They  are  made  in 
various  forms  and  sizes.  Circular  ones  are  usually  about  3  feet  6 
inches  in  diameter  and  3  feet  6  inches  high,  with  the  melting- 
chamber  20  to  24  inches  deep,  and  cost  about  $60.  The  rectangular 
ones  range  from  4  to  8  feet  in  length  and  from  3  to  4  feet  in 
width  and  from  2  to  4  feet  deep  at  centre  of  heating-chamber;  they 
range  in  price  from  $75  to  $500.  The  most  approved  form  is 
shown  in  Fig.  271.  It  is  constructed  with  double  bottom,  similar 


FIG.  272. — SWEEPING  MACHINE. 

to  a  double  boiler,  so  that  the  heating-surface  extends  the  full 
length  and  well  up  on  the  sides.  The  melting-chamber  is  made  of 
soft  steel.  Capacity  about  600  gallons;  weight  with  tongue,  double- 
tree, and  neck-yoke  3320  Ibs. 

1040.  Tools  for  Cleansing — HAND  TOOLS. — Brooms  for  street 
sweeping  are  made  of  steel  wire  or  rattan;  their  size  is  generally  16 
inches  long  by  4  inches  wide;  wire  lasts  longer  than  rattan,  but  is 
only  suitable  for  block  pavements. 

Price,  steel per  dozen  $12.00  to  $18.00 

«      rattan  "       "          8.50"       9.00 

SQUILGEES,  or  rubber  scrapers,  are  used  for  cleaning  asphalt 
pavements.  Price  per  dozen  $7.50  to  $9. 


TOOLS    AND    MACHINERY    EMPLOYED. 


71 


MECHANICAL  SWEEPERS. — A  variety  of  these  machines  are  in 
the  market,  and  in  various  sizes,  to  be  used  with  one  or  four  horses. 
Figs.  272  to  276  show  a  few  of  the  many  forms. 

The  sweeper  shown  in  Fig.  272  is  known  as  the  "Pride  of  New 
York."  The  broom  is  8  feet  6  inches  long,  and  sweeps  a  track  7 


FIG.  278.— SWETCPTNG  MACHINE. 


FIG.  274. — SWEEPING  MACHINE. 

feet  10  inches ;  it  weighs  complete  1900  Ibs.,  and  is  operated  by- 
two  horses,  and  costs  about  $400.  Smaller  machines  of  the  type 
are  also  manufactured,  to  be  operated  by  one  horse;  the  one- 
horse  machine  sweeps  a  track  5  feet  6  inches  wide,  weighs  1400 
Ibs.,  and  costs  about  $300. 


HIGHWAY   CONSTRUCTION. 


Fig.  273  shows  the  "Austin  Sweeper/'  It  is  made  of  steel 
throughout.  The  broom  is  8  feet  in  length  and  is  made  of  tem- 
pered flat  steel  wires  or  rattan,  and  sweeps  6  feet  wide.  It  is 
operated  by  two  horses. 

The  sweeper  shown  in  Fig.  274  is  known  as  the  "Barnard 
Castle."  It  is  made  in  England,  and  is  extensively  employed  both 


FIG.  275.— COMBINED  SWEEPER  AND  SPRINKLER, 


FIG.  27G. — COMBINED  SWEEPER  AND  SPRINKLER. 

in  that  country  and  in  America.  -  It  is  manufactured  in  two  sizes, 
yiz.,  to  sweep  six  feet  and  seven  feet  six  inches,  respectively.  The 
smaller  machine  is  made  either  with  shafts  for  one  horse  or  with  a 
pole  for  two  horses.  The  larger  machine  is  made  only  with  a  pole 
for  two  horses. 


TOOLS   AND   MACHINERY   EMPLOYED. 


COMBINED  SWEEPER  AND  SPRINKLER,  Figs.  275  and  276,  is 
designed  for  cleansing  either  stone,  wood,  or  asphalt  pavements. 
The  machine  consists  of  a  circular  water-tank  with  a  revolving 
brush  beneath  it.  A  water-pipe  or  spreader  travels  in  advance 
of  the  brush  and  facilitates  its  operation. 


FIG.  277. — SCRAPIJSG  MACHINE. 

SCRAPING  MACHINES. — For  the  removal  of  stiff  mud  and  snow 
from  pavements  scraping  machines  are  extensively  employed. 
They  generally  consist  of  a  number  of  steel  or  iron  teeth,  three  to 
five  inches  wide,  attached  to  a  frame  in  such  manner  that  they 
will  rise  and  pass  over  any  fixed  obstacle  without  suffering  injury. 

Fig.  277  illustrates  the  Barnard  Castle  street-scraper.  It  is 
drawn  by  either  one  or  two  horses,  and  delivers  the  mud  or  snow 
one  side  in  ridges,  similar  to  the  sweeping  machine.  The  extent  of 
surface  scraped  per  hour  by  one  of  these  machines  is  about  8000 
square  yards. 

Figs.  278  to  280  illustrate  two  forms  of  the  hand-cart  used  in 
cleaning  streets  by  the  "patrol,"  or  block  system.  Price  $25. 


774 


HIGHWAY    CONSTRUCTION. 


FIG.  278.— PATROL-CART. 


FIG.  279.  —PATROL-CART. 


TOOLS   AND   MACHINERY    EMPLOYED. 


775 


FIG.  280. — PATROL-CART. 


Fig.  281  shows  the  hand  scoop  used  by  the  street  patrol  in 
several  cities. 


FIG.  281.— HAND  SCOOP. 


HIGHWAY   CONSTRUCTION-. 


Fig.   .282  represents  a  hand  sweeping  machine  which  can  be 
operated  by  one  man.     Price  $65. 


FIG.  282.— HAND  SWEEPER. 


DUMP-CARTS. — The  cart  used  to  remove  street-sweepings  is 
shown  in  Fig.  283.  The  body  is  iron,  and  the  usual  dimensions  are 
seven  feet  long,  three  feet  eleven  inches  wide,  and  two  feet  six 
inches  deep,  and  capacity  one  and  one  half  tons. 


FIG.  283.— DUMP-CART. 


TOOLS   AND   MACHINERY   EMPLOYED. 


COMBINED  SWEEPING  AND  COLLECTING  MACHINE. — In  conse- 
quence of  the  increasing  use  of  improved  pavements,  and  with  the 
view  of  reducing  the  amount  of  manual  labor  required  with  the 
usual  form  of  side-sweeping  machines,  inventors  have  sought  to 
devise  machines  which  will,  instead  of  merely  sweeping  the  dirt 
into  windrows,  collect  and  pick  it  up.  Three  types  of  "pick-up" 
machines  are  now  on  the  market,  viz.,  the  "International,"  the 
"Universal,"  and  the  "Pneumatic." 

The  International  machine  (Figs.  284  and  285)  consists  of  an 
iron  collecting-box  and  a  revolving  broom.  The  box  has  hinged 
sides  and  bottom,  and  is  open  at  the  back  to  receive  the  dirt 
brushed  up  by  the  broom.  The  broom  is  entirely  enclosed,  and  the 


FIG.  284. — SWEEPING  AND  COLLECTING  MACHINE. 

back  part  of  the  casing  forms  a  receptacle  for  dirt  carried  over  bj 
the  broom,  and  which  would  otherwise  be  deposited  upon  the  sur- 
face already  swept.  The  operation  resembles  that  of  an  ordinary 
carpet-sweeper. 

The  machine  is  made  of  iron  and  steel,  is  mounted  on  four 
wheels,  and  is  drawn  by  two  horses.  The  broom  is  5  feet  long, 
and  revolves  on  a  stationary  spindle  running  through  a  tube  in  the 


HIGHWAY    CONSTEUCTIOK. 


centre  of  the  broom.  Medium-coarse  bass  is  used  for  the  broom, 
and  its  life  is  from  18  to  25  days.  The  collecting-box  has  a  ca- 
pacity of  one  cubic  yard,  but  it  cannot  be  filled  to  its  capacity,  as 
the  dirt  would  fall  back  upon  the  broom,  and,  in  fact,  the  dirt  has 
a  tendency  to  form  a  ridge  near  the  open  end  of  the  box,  which 
prevents  the  entrance  of  fresh  dirt  carried  up  by  the  broom,  so 
that  the  box  has  to  be  dumped  frequently  in  order  to  prevent  the 
dirt  from  dropping  back  on  the  street. 


FIG.  285.— SWEEPING  AND  COLLECTING  MACHINE. 

The  machine  weighs  about  2500  pounds,  sweeps  within  one 
foot  of  the  curb,  and  the  driver  can  regulate  the  pressure  of  the 
broom  on  the  pavement  or  throw  it  out  of  gear. 

This  machine  has  been  successfully  used  for  collecting  and  pil- 
ing the  dirt  swept  to  the  side  of  the  street  by  an  ordinary  side- 
sweeping  machine.  When  used  in  this  way,  it  is  said  it  saves 
the  cost  of  three  gutter-men,  and  half  the  teams  for  hauling  off 
the  sweepings,  as  the  wagons  can  be  loaded  much  more  quickly  on 
account  of  the  piling  of  the  dirt. 

The  Universal  machine  (Fig.  286)  consists  of  an  iron  frame 
carrying  a  diagonal  revolving  broom,  26  inches  in  diameter,  which 
sweeps  the  dirt  into  a  windrow.  Directly  in  line  with  this  wind- 
row, and  behind  the  delivering-end  of  the  long  broom,  is  a  short 
broom,  31  inches  in  diameter  and  2  feet  wide,  which  revolves  at 
two  and  a  half  times  the  speed  of  the  main  broom.,  and  drives  the 


TOOLS   AND   MACHINERY   EMPLOYED.  779 

material  of  the  windrow  into  a  chamber  at  the  base  of  an  endless- 
belt  elevator,  the  buckets  of  which  carry  up  the  dirt  and  dump  it 
into  a  chute,  through  which  it  falls  into  a  covered  bin  mounted  on 
the  frame  of  the  machine.  This  bin  is  carried  by  trunnion  bear- 
ings at  each  end,  and  when  full  a  dump  cart  is  driven  alongside  the 
machine,  and  the  bin  is  tilted  by  means  of  a  crank-handle  and 
gearing  to  discharge  its  load  into  the  cart. 


FIG.  286.— SWEEPING  AND  COLLECTING  MACHINE. 

The  machine  weighs  about  4000  pounds,  and  is  drawn  by  three 
horses;  the  capacity  of  the  bin  is  about  one  cubic  yard.  If  worked 
steadily  without  delays,  the  machine  can  sweep  about  a  mile  of 
street  an  hour. 

This  machine  has  been  successfully  tried  in  New  York  and 
Boston,  and  Mr.  H.  H.  Carter,  M.  Am.  Soc.  C.  E.,  Superintendent 
of  Streets,  Boston,  states  that  it  has  demonstrated  its  ability  to  do 
the  work  at  about  45  per  cent  of  the  cost  under  the  former  method, 
by  which  the  dirt  was  swept  into  windrows  by  ordinary  side-sweep- 
ing machines,  then  swept  by  hand  into  piles  and  shovelled  into 
dump-carts. 

The  Pneumatic  machine  works  by  an  air-blast.  It  consists  of 
an  iron  box  6£  feet  wide,  16  feet  long,  and  7-J  feet  from  the  ground 
to  the  top,  mounted  on  four  wheels,  and  equipped  with  an  exhaust 
fan  operated  by  a  5-horse-power  engine,  and  rectangular  brushes  or 
scratchers.  It  is  operated  by  two  men  and  three  horses,  and  in 
working  order  weighs  about  6000  pounds. 

In  operation  the  scratchers  drag  on  the  street  and  loosen  the 


HIGHWAY   CONSTRUCTION". 


dirt,  which  is  carried  by  the  air-blast  into  the  dirt-box.  The  ex- 
haust steam  is  used  to  dampen  the  dirt,  and  any  dust  that  may  be 
picked  up  is  carried  to  the  furnace  of  the  boiler.  The  dirt-box  has 
a  capacity  of  about  half  a  cubic  yard,  and  when  full  is  dumped, 
leaving  the  material  in  convenient  piles  for  shovelling  into  the 
dump-carts. 

SPRINKLING-CARTS  are  made  in  various  sizes,  and  of  wood,  iron, 
and  steel,  and  with  various  devices  for  controlling  and  spreading 
the  water. 

The  sprinkler  shown  in  Fig.  287  is  made  in  the  following  sizes: 

Price. 

1000  gallons $550.00 

750       "      475.00 

550      " 425.00 

350  .    " 400.00 


FIG.  287. — STREET-SPRINKLER. 

Fig.  288  shows  a  sprinkler  made  entirely  of  steel.     Throe  sizes 
are  on  the  market,  viz.,  600,  750,  and  1000  gallons. 

.  The  sprinkler  shown  in  Fig.  288a  is  styled  the  "  Contractor's 
Sprinkler."  The  gear  used  is  called  "Contractor's  Gear,"  and  dif- 
fers from  an  ordinary  farm  gear  in  that  the  reach  is  dovetailed 


TOOLS  AND  MACHINERY  EMPLOYED. 


18! 


FIG.  288.  —  STKKET-SPUIN K LER. 


FIG.  288a.— CONTRACTOR'S  SPRINKLER. 


782 


HIGHWAY    CONSTRUCTION. 


into  and  firmly  bolted  and  braced  to  botli  the  front  and  hind  bol- 
sters, coupling  the  two  gears  together  rigidly.  The  bolsters  being 
thus  kept  in  line  and  immovable  as  compared  to  each  other,  the 
tank  rests  firmly  on  them  and  the  bolster-spring  cases  are  not  subject 
to  any  lateral  strain.  The  front  gear  is  so  constructed  that  the  front 
wheels  cut  under  until  they  strike  the  reach,  making  it  possible  to 
turn  very  short.  The  tongue  is  stiff  and  is  held  up  firmly  by  sway 
bars  pressing  against  the  under  side  of  the  reach  and  is  heavily 
ironed  its  entire  length  with  continuous  iron.  The  axles  are  of 


FIG.  288&.— STREET  SPRINKLER. 

solid  steel,  firmly  clipped  to  the  wood  stocks.  The  tank  is  made 
of  wood  and  rests  on  double  coil-bolster  springs  in  cast-iron  cases; 
it  can  be  lifted  off  the  gear  and  set  to  one  side,  thus  allowing  the 
use  of  the  gear  in  other  hauling  work.  This  combination  is  much 
in  favor  with  contractors.  The  sizes  and  prices  are  as  follows : 

No.  46.  750  gallons  capacity,  2£"  front  and  2f"  bind  axles $310.00 

No.  47.  600  gallons  capacity,  2fc"  front  and  2±"  hind  axles. . . .  $255.00 

Fig.  288Z>  shows  the  standard  platform  spring-gear  sprinkling 


TOOLS   AND    MACHINERY    EMPLOYED. 


783 


wagon  which  has  been  adopted  by  the  Street  Sprinkling  Association 
of  New  York  City.     It  is  made  in  various  sizes  as  follows: 

No.  28$.  450  gallons  capacity $315.00 

No.  27.     600  gallons  capacity 325.00 

No.  26.     750  gallons  capacity 365.00 

SNOW-PLOUGHS. — The  ploughs  employed  for  the  removal  of 
enow  on  country  highways  are  usually  made  of  wood.  The  general 
form  is  shown  in  Figs.  289  and  290.  They  are  loaded  with  stone. 
In  light  falls,  say  of  6  inches,  one  horse  is  sufficient,  but  in  deeper 
falls  two  or  more  are  necessary. 

Side  View.  Side  View. 


Plan. 
FIG.  289. 


SNOW-PLOUGHS. 


Plan. 
FIG.  290. 


Snow-shovels per  dozen  $4.50 

Sidewalk-chisels , "         $7.00  to  $17.00 

MACHINES  FOR  MELTING  SNOW  have  been  experimented  with 
in  various  cities — the  results  have  not  been  entirely  satisfactory — 
the  capacity  being  low  and  the  cost  of  operating  high.  A  machine 
using  naphtha  as  fuel  was  tried  in  New  York  City  in  1897  for 
which  is  claimed  a  melting-capacity  of  60  cubic  yards  per  hour  at 
a  cost  of  $8.  .'••.- 


784 


HIGHWAY    CONSTRUCTION. 


1041.  Tools  Employed  for  Artificial  Stone  Pavements. — 
TAMPERS  (Fig.  291). — Cast  iron,  with  hickory  handle;  range  from 
6X8  inches  to  8  X  10  inches.  Price  from  $2  to  12.50  each. 


FIG.  291. 


FIG.  292. 


FIG.  295. 


FIG.  294. 


FIG.  296. 


FIG.  297. 


TOOLS   AND    MACHINERY    EMPLOYED. 


QUARTER-BOUND,  Fig.  292,  is  used  for  rounding  corners  and 
sedge.  Made  of  any  desired  radius.  Price  from  $1.75  to  $3  each. 

JOINTER,  Fig.  293,  is  used  for  trimming  and  finishing  the  joints. 
Price  from  $2  to  $3  each. 

CUTTER,  Fig.  294,  is  used  to  cut  the  concrete  into  blocks. 
Price  $3  each. 


FIG.  298. — CAST-IRON  CATCH-BASIN, 

GUTTER-TOOL,  Fig.  295,  is  used  for  forming  and  finishing  gutters. 
Price  $2.50  each. 

IMPRINT-ROLLERS. — Figs.  296  and  297  show  two  designs  of 
rollers  for  imprinting  the  surface  of  artificial  stone  pavements  with 
grooves,  etc.  Price  ranges  from  $8  to  $15  each. 


786 


HIGHWAY   CONSTRUCTION". 


1042.  Catch-basins,  Sewer  Inlets,  and  Gutter-crossings,— Fig. 
298  illustrates  a  catch-basin  made  of  cast  iron,  which  is  introduced 
as  a  substitute  for  the  brick  chambers  now  generally  used.  It  is 
easily  put  together  without  skilled  labor,  and  each  piece  or  section 
is  light  enough  to  be  handled  readily.  The  front  opening  is  1  foot 
high  and  4-J-  feet  wide,  protected  by  a  wrought-iron  grating,  so 
formed  that  floating  refuse  will  not  lodge  and  close  the  opening. 
Price,  corner  inlet  $125;  side  inlet  $115. 

Fig.  299  shows  a  catch-basin  cover  and  grating  for  use  as  a  side 


FIG.  299.— SIDE  INLET. 

inlet.     The  grate-opening  is  12  X  24  inches, 
removing  sediment  is  24  inches  in  diameter. 


The  lid  or  cover  for 
Price  $16. 


FIG.  300.—  GUTTER-GRATING. 


Fig.  300  shows  a  cast-iron  gutter-box  designed  to  fit  into  the 
hub  of  a  10-inch  sewer-pipe,  and  is  suitable  for  use  on  highways,. 


TOOLS  AND  MACHINERY  EMPLOYED. 


»v  orv 
I  Of 


park  walks  and  streets.  Dimensions  on  top,  9  inches  long,  6  inches 
wide,  and  3  inches  deep;  total  height,  4£  inches;  weight  about  20 
pounds.  Price  $2.50. 

Among  the  appliances  invented  for  the  purpose  of  closing  the 
street  inlets  to  sewers  against  the  escape  of  gases,  etc.,  may  be 
mentioned  the  Hitchcock  patent  sewer  inlet-trap  (Fig.  301).  The 


FIG.  301. — THE  HITCHCOCK  SEWER  INLET- TRAP. 


FIG.  302. 


FIG.  303. 


device  explains  itself;  the  purpose  is  to  prevent  the  escape  of 
gases  from  the  sewer  during  the  cooler  seasons,  when  the  air  in  the 
sewer  is  usually  warmer  than  the  air  in  the  streets.  The  lid  A 
opens  and  permits  the  discharge  of  water  entering  the  inlet;  but  at 


788 


HIGHWAY    CONSTRUCTION". 


other  times  it  remains  tightly  closed  by  its  own  weight  against  the 
fixed  spout  D.  The  trap  is  made  of  cast  iron,  and  has  been  suc- 
cessfully used  in  Springfield,  Mass.,  for  about  fifteen  years.  The 
price  is  about  $4.50;  including  the  grate  and  rim,  which  is  18 
inches  in  diameter  and  weighs  about  175  pounds,  the  price  is  $9. 

Figs.  302  and  303  show  a  cast-iron  inlet  and  manner  of  setting 
designed  for  conducting  storm-water  from  the  side  ditches  of  im- 
proved suburban  or  country  roads  into  the  under-drains. 


FIG.  304.— GUTTER-CROSSING. 


FIG.  305.— GUTTER-CROSSING  PLATE. 

The  inlet-head  is  of  cast  iron,  with  a  removable  grate  of  wrought 
iron,  which  is  placed  at  an  angle  of  60  degrees,  to  correspond  with 
the  slope  of  the  bank.  It  is  provided  with  flanges  to  rest  upon  a 
brick  or  stone  foundation,  is  circular  in  form  and  18  inches  in 
diameter,  and  can  be  reduced  to  fit  any  desired  size  of  pipe.  Price, 
without  reducer,  $6;  with  reducer,  $7. 

Figs.  304  and  305  show  two  forms  of  gutter-crossings.     Fig.  302 


TOOLS   AND    MACHINERY    EMPLOYED.  789 

is  made  in  widths  from  4  to  26  inches,  and  from  4  to  10  inches  in 
depth,  and  in  lengths  from  3  to  6  feet.  Price  per  foot  ranges  from 
$1.30  for  the  smaller  sizes  to  $7. GO  for  the  larger.  Fig.  303  is 
made  in  sections  30  inches  wide  and  5  feet  long.  Price  $12  each. 


."*••'.         FlG.  306.—  GOTTEll-BOXES   AND    GRATINGS. 

Fig.  306  shows  cast-iron  gutter-boxes  and  gratings  for  use  with 
catch-basins.  They  are  made  in  sizes  from  4  feet  long,  1  foot  wide, 
and  9  inches  deep  to  15  inches  long,  9  inches  wide,  and  9  inches 
deep.  Prices  range  from  $25  for  the  largest  size  to  $3.75  for  the 
smallest. 

1042a.  Street  Name-plates. — The  custom  of  using  tablets  of 
pottery  and  stone  built  into  buildings  was  resorted  to  by  the 
Romans,  both  tb  name  streets  in  large  towns,  and  to  direct  way- 
iarers  from  one  place  to  another.  Until  the  early  part  of  the  pres- 
ent century  the  names  of  streets  and  roads  were  usually  painted  or 
carved  on  boards,  and  sometimes  the  names  were  inscribed  en 
stone,  and  in  one  instance  on  slate.  Regarding  the  durability  of 
the  latter,  Mr.  Francis  Smythe,  C.E.,  states  that  he  saw  in  Wales  a 
direction  notice  written  in  slate  which  was  stated  to  have  been  in 


790  HIGHWAY   CONSTRUCTION. 

existence  for  over  a  century,  and  it  showed  but  little  ill  effect  from 
the  action  of  the  weather. 

It  was  not  until  about  the  third  or  fourth  decade  of  the  present 
century  that  cast  iron  was  known  to  be  used  for  this  purpose, 
having  been  previously  introduced  as  mile-posts.  At  the  present 
time  in  Europe  probably  more  name-plates  of  this  metal  are  used 
than  any  other  kind,  although  many  devices  have  been  introduced. 
Among  these  may  be  mentioned  enamelled  iron  plates;  plates  made 
of  an  alloy  containing  a  large  proportion  of  zinc;  embossed  or  raised 
letters  on  sheet-iron  and  zinc  plates,  or  letters  cut  out  of  the  same 
metals;  china  or  glass  letters  fastened  on  to  wood  or  metal  plates; 
plates  made  entirely  of  glass,  glazed  terra-cotta,  or  china;  metal 
plates  let  into  the  surface  of  foot-paths;  glass  slips  fastened  into  the 
lanterns  of  public  lamps;  and  metal  plates  fastened  to  the  lamp- 
columns  or  to  independent  columns. 

Cast-iron  name-plates  have  hitherto  been  most  in  use  on 
account  of  their  cheapness  and  durability,  the  objections  to  them 
being  their  brittleness  and  consequent  liability  to  fracture,  scaling 
of  the  paint,  and  corrosion. 

Enamelled- iron  name-plates  are  extensively  used.  They  are 
neat  in  appearance,  and  can  be  read  from  quite  a  distance.  The 
colors  generally  employed  are  white  for  the  letters  and  dark  blue 
for  the  background.  The  letters  are  usually  2|  inches  in  height. 
Enamelled  signs  deteriorate  when  subjected  to  frequent  changes  of 
temperature.  The  difference  in  expansion  between  the  enamel  and 
the  backing  causes  the  former  to  crack  and  scale,  and  when  the 
backing  commences  to  oxidize  the  lettering  is  quickly  obliterated. 
Many  manufacturers  claim  that  their  plates  are  proof  against  this 
defect,  but  experience  shows  that  all  are  liable  to  this  fault. 

Wood  is  extensively  used  for  name-plates.  Oak  is  preferred.  It 
should  be  well  braced  across  the  grain  to  prevent  warping.  With 
gilt  letters  on  a  sanded  black  surface,  wood  makes  a  sign  satisfac- 
tory in  appearance  and  durability,  and  not  very  expensive. 

As  a  rule  street  name-plates  are  made  too  small  and  not  suffi- 
ciently prominent.  An  extra-sized  letter  (24  to  4  inches)  does  not 
add  a  very  large  proportion  to  the  cost,  as  the  time  of  fixing,  which 
is  a  considerable  portion  of  the  expense,  would  not  take  any 


TOOLS   AND    MACHINERY    EMPLOYED.  791 

longer.  A  bold  moulding  round  the  plate  increases  its  promi- 
nence. 

Various  methods  have  been  suggested  for  placing  the  names  in 
the  sidewalk.  Among  those  tried  may  be  mentioned  the  cutting 
of  the  name  in  the  top  of  the  curbstone  and  coloring  the  letters 
black.  Where  concrete  is  used  for  the  sidewalk,  wooden  pattern 
letters  1  inch  deep  are  bedded  in  the  concrete,  which,  when  the 
concrete  is  sufficiently  set,  are  removed  and  the  space  filled  with 
colored  cement  mortar  or  letters  made  of  brass  or  composition 
metal. 

The  streets  of  St.  Louis  are  posted  with  enamelled  signs  having 
clear  white  letters  on  a  dark  blue  ground.  The  plates  for  these 
signs  are  4£  inches  wide,  from  16  to  26  inches  long,  and  are  made 
of  No.  18  wrought  iron,  United  States  standard  gauge.  At  the 
middle  of  the  sides  and  ends  and  three-eighths  of  an  inch 
from  the  edge  of  the  plate  are  the  four  screw-holes,  No.  9  brass 
screws  being  used.  Where  posts  are  used  they  are  of  cypress  or 
cedar,  4x4  inches  in  section  and  12  feet  long.  The  signs  are 
screwed  on  seven-eighths-inch  clear  pine  kiln-dried  lumber,  painted 
with  one  coat  of  asphaltic  paint.  The  letters  on  the  signs  are  half 
block  and  three  inches  high.  Numbered  streets  from  First  Street 
to  Ninth  Street,  inclusive,  are  spelled  out  in  full,  but  from  10th 
Street  up  figures  are  used,  followed  by  "  nd,"  "rd,"  or  "th,"  as  may 
be  called  for.  The  word  "  Street "  is  spelled  out  in  full  on  the 
numbered  streets.  On  named  streets  the  abbreviation  "  St."  is 
used  after  the  name.  Avenue  is  abbreviated  to  "Av.";  Boulevard 
to"Bl.";  Place  to  "PL";  and  "Road"  to  "  Rd."  No  periods  are 
used  except  after  abbreviations.  The  enamel  of  the  ground  color 
on  the  plates  is  a  dark,  glossy  blue,  free  from  lumps  and  blisters, 
and  guaranteed  not  to  exude  white  powder  when  exposed  to  the 
atmosphere.  The  lettering  is  a  clear  white,  free  from  dark  spots. 
The  back  of  the  plate  is  thoroughly  coated  with  enamel,  and  before 
acceptance  the  plates  are  subjected  to  an  impact  and  bending  test, 
any  sign  of  flaking  or  scaling  being  rejected.  The  cost  was  36£ 
cents  each,  delivered. 

1042b.  Direction  Indicators  should  be  placed  at  junctions  and 
crossing  of  roads  for  the  convenience  of  travellers.  They  should  be 
substantially  made  of  an  imperishable  material,  bold  and  neat  in 


792  HIGHWAY    CONSTRUCTION. 

design,  with  strong  self-bracing  bases.  The  lettering  should  be 
bold  and  legible,  the  direction  arms  easily  fixed  at  any  angle  with- 
out the  necessity  for  special  castings  or  complicated  fastenings. 

1042c.  The  Viagraph  (Fig.  307),  invented  by  Mr.  I.  Brown,  is  an 
instrument  for  ascertaining  and  registering  the  inequalities  in  road, 
surfaces,  so  that  any  given  road  may  be  compared  with  another,  or 
with  itself  at  different  times.  In  principle  the  viagraph  is  a  straight- 
edge applied  continuously  to  the  road-surface  along  which  it  may 
be  drawn,  and  conveying  an  apparatus  for,  first,  recording  on  paper 
a  profile  of  the  road-surface;  and,  secondly,  indicating  a  numerical 
index  of  the  unevenness  of  the  surface. 

Fig.  307  gives  a  view  of  the  instrument  with  the  cover  removed. 
The  frame  is  in  form  like  a  sled,  with  straight  runners  on  which  are 


FIG.  307. 

mounted  the  working  parts.  The  lever  T,  pivoted  to  the  main 
frame  at  If,  carries  on  its  free  end  a  toothed  wheel,  the  upper  part 
of  which  is  seen  at  V.  While  the  main  frame  in  being  drawn 
along  the  road  preserves  a  sufficiently  even  line,  the  road-wheel  V 
rises  and  falls  over  all  the  unevennesses  of  the  surface,  carrying 
with  it  the  lever  T,  and  thereby  transmitting  its  movements  by 
means  of  the  link  and  lever  S  to  the  pencil  P  (raised  abnormally  in 
the  figure)  and  recording  them  on  the  roll  of  paper  drawn  from  the 
stock  roll  C  and  wound  upon  the  receiving-drum  B.  The  profile 
thus  made  is  of  full  size,  vertically,  and  £  inch  in  to  1  foot  horizon- 
tally. The  second  pencil  seen  below  P  draws  a  datum  line  with 
which  that  drawn  by  pencil  P  would  concide  if  the  road  were  per- 
fectly even.  The  sum  of  the  vertical  registration  of  the  pencil  P 
is  called  "  the  numerical  index  of  unevenness,"  and  is  recorded 
automatically  by  the  decimal  counter  W  operated  by  a  cord  attached 
to  the  free  end  of  the  lever  T  and  passing  once  around  a  double- 
grooved  pulley  X. 


CHAPTER  XXIV. 


MISCELLANEOUS  NOTES. 

1043.  Comparison  of  European  and  American  Methods  and 
Prices. — Comparison  is  frequently  made  between  the  methods  and 
cost  of  constructing  and  maintaining  roads  and  pavements  in  the 
United  States  and  Europe.  In  making  such  comparisons  it  must 
be  remembered  (1)  that  comparisons  are  of  little  value  unless  based 
upon  similar  conditions;  (2)  that  the  cost  of  materials  and  labor  in 
Europe  is  generally  much  less  than  in  America;  (3)  that  the 
methods  and  cost  will  vary  very  much  in  different  parts  of  the 
same  country  ;  (4)  that  the  cost  of  constructing  and  maintaining 
roads  and  pavements  depends  upon  many  diverse  elements,  due  to 
local  conditions,  customs,  and  habits,  as  well  as  upon  the  quality  of 
the  materials,  distance  of  transport,  skill  of  the  workmen,  charac- 
ter of  the  traffic,  climatic  conditions,  etc. 

Although  it  is  evident  that  comparisons  based  upon  such  vari- 
able elements  as  are  enumerated  above  must  be  imperfect,  never- 
theless intelligent  observation  and  comparison  of  the  methods  and 
cost  of  construction  and  maintenance,  both  at  home  and  abroad, 
will  materially  aid  in  avoiding  unnecessary  expenditure  in  experi- 
ments, and  will  promote  economy  and  efficiency. 

Table  No.  LXXXVIII  shows  the  wages  paid  in  several  European 
localities. 

TABLE  LXXXVIII. 


Kind  of  Labor. 

London. 

Berlin. 

Paris. 

England. 

Bel- 
gium. 

France. 

$0.58 
$20.00t 

$1.55 

Unskilled  

$0.60 
$1.00  to  $2.00 
$1.75 
$0.80 
$1.50 
$2.00  to  $2.50 
$1.75 

$0.48  to  $0.70 
$0.83 
$1.50 
$0.71 

$1.60  to  $1.80 
$1.50 

$0.80 
$0.90  to  $1.20 
$1.20 
$080 
$0.90  to  $1.10 

$1.60 

$1.56  to  $1.75 
$1.00 

$0.80  to  $0.90 
$0.80  to  $1.44 
$1.75  to  $2.50 
$1.25 

$0.06  to 
$0.07* 

Foreman    
Pavers  

Sweepers  
Steam-roller  drivers. 
Horse  and  cart  
Masons  

*  Per  hour. 


t  Per  month. 


793 


794  HIGHWAY   CONSTRUCTION. 

Iii  European  cities  10  hours  constitute  a  day's  labor. 

Wages  in  the  United  States  range  between  the  following  limits, 
and  a  day's  work  varies  from  8  to  10  hours : 

Foremen,  $3  to  $5. 

Sub-foremen,  $1.75  to  $2.50. 

Unskilled,  $1.25  to  $1.75. 

Pavers,  $2.50  to  $4.50. 

Masons,  $3  to  $4.50. 

Steam-roller  drivers,  $3  to  $4.50. 

Single  horse,  cart,  and  driver,  $2.50  to  $3.50.    , 

Double  horse,  wagon,  and  driver,  $3  to  $6. 

Drillers,  $2  to  $3. 

Sweepers,  $1.25  to  $2. 

1043a.  Statistics  of  Roads  in  the  United  States.— The  following 
statistics  concerning  the  weight  of  load  for  horses,  cost  of  haulage, 
and  length  of  haul  from  farms  to  markets  are  deduced  from  the 
investigation  conducted  by  the  office  of  Road  Inquiry  of  the  De- 
partment of  Agriculture. 

AVERAGE  WEIGHT  OF  LOAD  FOR  TWO  HORSES. 

Eastern  states , 2216  pounds 

Northern  states 2136 

Middle  Southern  states 1869 

Cotton  states 1397 

Prairie  states 2409 

Pacific  coast  states 2197 

Average  for  the  United  States 2002 

AVERAGE  COST  OF  HAULAGE  PER  TON  PER  MILE 

Eastern  states 32  cents 

Northern  states 27  " 

Middle  Southern  states     31  " 

Cotton  states 25  " 

Prairie  states 22  " 

Pacific  coast  states 22  " 

Average  for  the  United  States 25  " 


MISCELLANEOUS    NOTES.  795 


AVERAGE  LENGTH  OF  HAUL  IN  MILES  FROM  FARMS  TO 
MARKET  OR  SHIPPING  POINTS. 

Eastern  states 5.9  miles 

Northern  states 6.9  " 

Middle  states 8.8  " 

Cotton  states 12.6  " 

Prairie  states 8.8  " 

Pacific  coast  states 23.3  " 

Average  for  United  States . .  .12.1  " 

AVERAGE  TOTAL  COST  PER  TON  FOR  THE  WHOLE  LENGTH  OP 

HAUL. 

Eastern  states $1.89 

Northern  states 1.86 

Middle  Southern  states 2.72 

Cotton  states 3.05 

Prairie  states '. 1.94 

Pacific  coast  states 5  12 

Average  for  the  United  States 3.02 

In  conquence  of  the  great  attention  which  highway  improve- 
ment is  now  receiving  and  the  agitation  for  the  construction  of 
light  railways  connecting  the  markets  and  shipping  points  with 
the  farms,  accurate  and  reliable  information  as  to  the  cost  of  haul- 
age over  country  roads  is  in  demand,  and  the  above  figures,  if  trust- 
worthy, will  be  received  with  much  satisfaction. 

The  accurancy  of  the  figures  cannot,  however,  be  tested  with- 
out a  knowledge  of  the  condition  of  the  roads  at  the  time  the 
observations  were  made.  If  they  were  earth  in  a  dry  and  hard  con- 
dition, the  cost  seems  high ;  but  if  they  were  earth  covered  with 
mud  and  ruts  or  dry  sand  they  are  riot  excessive.  See  also  Table 
I,  page  3. 

1043b.  Sprinkling  Oil  on  Roads. — Crude  petroleum  has  recently 
been  used  on  country  and  park  roads  for  the  purpose  of  (1)  reduc- 
ing or  abating  the  dust,  (2)  securing  a  non-absorbent  surface,  which 
will  turn  off  rain-water,  and  (3)  a  dark-colored  road-surface,  which 
will  be  more  pleasing  to  the  eye  than  the  ordinary  light  color. 

The  Department  of  Parks  of  the  city  of  Boston  has  experimented 
with  sprinkling  the  driveways  with  crude  oil  to  lay  the  dust.  The 
amount  of  oil  used  was  0.6  gallon  per  lineal  foot  of  roadway  40  feet 
wide.  The  roadway  was  hard  and  smooth,  and  the  effect  of  the 
oil  seemed  to  De  a  slight  disintegration  of  the  surface  or  loosening 


HIGHWAY    CONSTRUCTION. 


of  the  bond  of  the  macadam.  The  small  stones  thus  loosened  were 
soon  crushed  into  powder,  and  formed  a  layer  on  the  surface  at  least 
^  inch  thick,  sufficiently  permeated  with  oil  to  prevent  it  from 
being  blown  by  any  but  strong  winds. 

During  a  period  of  two  months  on  that  part  of  the  roadway 
subjected  to  dust  the  treatment  resulted  in  the  abatement  of  the 
dust.  One  disadvantage  of  the  use  of  oil  for  park  work  is  its  dis- 
agreeable odor.  The  experiment  was  not  considered  so  fruitful  of 
good  results  as  to  induce  the  department  to  continue  it.  There  is  no 
question,  however,  but  that  it  will  effectually  lay  the  dust.  Super- 
intendent Pettigrew  suggests  that  on  a  hard  macadam  road  it  would 
be  a  good  plan  to  spread  a  layer  of  loamy  sand  to  receive  the  oil  in 
order  to  prevent  the  disintegration  of  the  surface  of  the  macadam. 

The  experiment  of  sprinkling  with  oil  the  roads  in  Los  Angeles 
Co.,  Gal.,  and  in  Jacksonville  Fla.,  is  considered  a  success. 

In  applying  the  oil  it  must  be  thoroughly  mixed  with  the  dust. 
If  it  is  merely  sprinkled  on  the  surface,  only  the  top  layer  of  dust 
will  be  impregnated;  the  wheels  of  vehicles  will  break  up  the  cake 
thus  formed,  exposing  the  dust  below,  and  the  road  will  be  more 
disagreeable  than  before.  Oil  applied  to  a  hard  road  to  prevent  the 
formation  of  dust  will  remain  on  the  surface  and  be  very  disagreeable. 

A  process  for  applying  the  oil  has  been  patented  by  F.  W.  Mat- 
tern  of  Los  Angeles,  Cal.,  in  which  there  is  mixed  a  high-test,  heavy 
oil  with  maltha.  This  compound  is  spread  upon  the  road  in  parallel 
lines  about  six  inches  apart,  in  sufficient  quantity  to  saturate  the 
dry  dust,  and  is  then  thoroughly  incorporated  by  the  use  of  rakes. 
Seven  and  a  half  gallons  are  applied  to  a  square  rod  if  the  dust  is 
half  an  inch  thick.  Water  is  then  sprinkled  upon  the  surface  and 
the  road  rolled;  it  is  then  ready  for  travel. 

The  machine  for  distributing  the  oil  consists  of  a  tank  six  feet 
long,  mounted  on  two  wheels,  and  in  use  is  attached  to  the  rear  of  an 
oil-tank  wagon.  The  oil  is  discharged  through  tubes,  six  inches 
apart,  controlled  by  valves  which  are  operated  by  a  lever.  The 
machine  is  furnished  with  hoes,  one  set  of  which  form  the  furrows 
in  which  the  oil  flows,  and  the  other  set  cover  it  with  the  dust.  A 
set  of  teeth  are  also  attached  which  incorporate  the  earth  and  oil. 

NOTE. — For  other  experiments  see  Report  Massachusetts  Highway  Com 
mission,  1898,  and  Sixth  Annual  Report  of  the  Commissioner  of  Public  Roads 
of  New  Jersey. 


MISCELLANEOUS    NOTES. 


1044.  Pavements  and  Horseshoes. — A  horse's  hoof  shod  with  a 
heavy  iron  shoe  strikes  a  blow  resembling  that  struck  by  a  hammer  in 
the  hand  of  man,  but  with  considerably  more  energy.  When  the  shoes 
are  furnished  with  sharp  toe-pieces  and  heel-calks,  as  in  the  pre- 
vailing form,  the  combined  effect  of  a  cutting  chisel  and  hammer  is 
produced.     This  form  of  shoe  is  rendered  necessary  to  obtain  foot- 
hold on  the  rough  and  ill-conditioned  pavements  generally  found 
in  use,  but   on  smooth   improved   pavements   it  is  not  required. 
Indeed,  its  use  produces  exceedingly  destructive  effects.     Broken- 
cstone  pavements  suffer  the  most ;  the  surface  is  excavated  and  the 
stones  displaced.     Block  pavements  also  suffer  considerably;   the 
blocks  are  chipped  and  rounded  until  they  assume  the  form  of 
boulders.     Wood  and  asphalt  probably  suffer  the  least,  unless  the 
blows  fall  successively  in  the  same  place. 

The  European  pavements  are  not  subjected  to  the  destroying 
effect  of  this  form  of  shoe.  There  smooth,  flat  shoes  of  light  weight 
are  used,  and  in  many  localities  the  form  of  the  shoe  is  regulated  by 
law. 

Fiat  shoes  and  wide  tires  have  a  large  effect  in  the  conservation 
of  pavements,  and  where  improved  pavements  have  been  intro- 
duced the  imposition  of  a  tax  would  be  warranted  to  hasten  their 
use. 

1045.  Annual  Cost  of  Structures. — The  annual  cost  of  any  struc- 
ture, or  the  annual  payments  required  to  maintain  the  structure 
in  perpetuity,  is  composed  of  three  elements: 

(1)  Interest  on  First  Cost. — If  the  structure  is  built  with  bor- 
rowed money,  interest  must  be  paid  as  a  matter  of  course  and  charged 
against  the  structure.  If  it  be  not  borrowed,  but  furnished  by  the 
owner,  the  case  is  not  essentially  different.  He  takes  it  from  some 
other  investment  which  would  pay  interest,  and  is  a  loser  if  the  new 
structure  does  not  make  him  the  same  return.  Any  structure 
which  cannot  bear  this  charge  of  interest,  is  a  bad  investment.  But 
if  the  structure  be  neither  built  nor  bought,  but  inherited  by  its 
present  owner,  its  first  cost  to  him  is  what  he  could  sell  it  for;  if  it 
have  no  market  value,  its  cost  to  him  is  nothing,  and  he  may  omit 
the  interest  charge  entirely. 

The  general  principle  is  that  the  cost  of  any  structure  is  the 
amount  of  capital  which  its  owner  voluntarily  keeps  in  it,  and  that 
on  this  amount  the  interest  must  be  charged  against  the  structure. 


798  HIGHWAY    CONSTRUCTION. 

(2)  Annual  Repairs. — Under  this  head  is  included  every  expense 
of  preserving  the  property,  such  as  ordinary  repairs,  watchmen,  in- 
surance, etc.     If  by  these  means  the  property  is  maintained  in  its 
original  condition,  "  as  good  as  new,"  these  two  elements  embrace 
the  whole  annual  cost.     But  there  are  many  cases  in  which  this  is 
not  true.     In  spite  of  the  annual  repairs,  the  structure  after  a,  time 
wears  out  and  must  be  replaced  either  in  whole  or  in  part  by  a  new 
one.     If  it  be  a  bridge,  it  has  to  be  rebuilt;  if  it  be  a  pavement  or  a 
set  of  rails,  they  have  to  be  taken  up  and  replaced  by  new  ones. 
This  makes  a  further  payment  necessary,  viz. : 

(3)  Annual  Payments  to  the  Renewal  Fund. — By  this  is  meant 
the  proportion  of  the  sum  finally  needed  to  renew  the  structure 
chargeable  to  each  year.     If  this  fund  be  raised  all  at  once  when  it 
is  actually  needed,  the  amount  chargeable  to  each  year  is  the  total 
sum  divided  by  the  number  of  years  in  the  life  of  the  structure. 
But  the  amount  of  each  contribution  will  be  made  very  much 
smaller  if  it  is  actually  paid  each  year  and  each  payment  improved 
at  compound  interest  after  the  manner  of  an  ordinary  sinking  fund 
for  the  extinction  of  bonds.     This  method  distributes  the  burden 
equally  over  the  whole  term  and  makes  it  much  lighter  than  is  pos- 
sible in  any  other  way.     Taking  it  for  granted  that  this  is  the  plan, 
adopted,  the  formula  to  ascertain  the  value  of  these  elements  will 
be  as  follows : 

Let  x  =  total  'annual  cost,  or  the  annual  payments  needed  ta 
maintain  the  structure  in  perpetuity; 

a  —  first  cost : 

#  =  value  of  old  materials  when  no  longer  fit  for  use  in  the 
structure,  and  also  the  value  of  so  much  of  the  struc- 
ture as  needs  no  renewal; 

c  =  cost  of  annual  repairs; 

n  =  number  of  years  the  structure  lasts  before  renewal; 

r  =  rate  of  interest  on  money; 
m  =  amount  or  final  value  of  an  annuity  of  $1.00  com- 

(1  -f  r)n  -  1 
pounded  each  year  for  n  years,  =  -  — ; 

The  final  cost  of  renewal  =  a  —  b.    If  the  renewals  should  exceed 
first  cost,  b  will  equal  the  excess,  and  the  total  cost  of  renewal  will 

=  a  -j-  b. 


MISCELLANEOUS   NOTES.  799 


To  find  the  annual  payment  to  the  renewal  fund,  call  it^?. 
Then  will  1  :  m  :  :  p  :  a  —  b. 


Whence  p  =  -      -  =  (a  —  b). 


The  annual  interest  charge  will  be  =  ar. 

The  total  annual  cost  of  the  structure  will  therefore  be 


The  factor  (1  -J-  r)n  is  the  amount  of  one  dollar  at  compound 
aterest  for  n  years  and  is  given  in  Table  LXXXIX. 

The  value  of  the  whole  expression  •.          \»  —  1  *s  giyen  *n  Table 
[C. 

As  an  example  of  the  application  of  the  formula,  let  the  problem 
>e  to  determine  the  relative  economy  of  a  wooden  and  an  iron  bridge 
or  a  given  place.     Let  the  length  of  the  bridge  be  500  feet,  or  4 
pans  of  125  feet  each,  and  let  the  other  data  be  as  follows : 
For  the  wooden  bridge 
a  =  first  cost  =  $25  per  foot.=  $12,500; 
b  =  value  of  iron  when  the  bridge  is  worn  out;  =  say  $2  per 

foot.  =  $1.000; 

c  =  cost  of  annual  repairs  =  $1200; 
n  =  life  of  the  bridge  =  10  years; 
r  —   6  per  cent  =  Tf Tr. 

:hen  will  x  =  $750  +  $1200  +  ($12,500 X. 0759)  =  $2822.85. 
For  the  iron  bridge 

a  =  first  cost  =  $50  per  foot.  =  $25.000.; 
b  =  value  of  old  materials  =  say  $10  per  foot.  =  $5000; 
c  =  annual  repairs  =  say  $500; 
n  =  life  of  bridge  =  say  60  years; 
r  =  6  per  cent  =  T  J^. 

'hen  will  x  e   $1500  +  $500  +  ($20,000  X  .0019)  =  $2038. 
Showing  a  saving  of  $784  per  annum  by  using  the  iron  bridge. 


800 


HIGHWAY   CONSTRUCTION. 


TABLE  LXXXIX. 

VALUE  OP  (1  +  r)w»  OR  THE  AMOUNT  OF  $1  AT   COMPOUND  INTEREST  FOB 
A  TERM  OF  YEARS. 

Interest  2  per  cent. 


Years. 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

$1.020 

21 

$1.516 

41 

$2.252 

2 

1.040 

22 

1.546 

42 

2.297 

3 

1.061 

23 

1.577 

43 

2.343 

4 

1.082 

24 

1.608 

44 

2.390 

5 

1.104 

25 

1.641 

45 

2.438 

6 

1.126 

26 

1.673 

46 

2.487 

7 

1.149 

27 

1.707 

47 

2.536 

8 

1.172 

28 

1.741 

48 

2.587 

9 

1.195 

29 

1.776 

49 

2.639 

10 

1.219 

30 

1.811 

50 

2692 

11 

1.243 

31 

1.848 

55 

2.972 

12 

1.268 

32 

1.885 

60 

3.281 

13 

1.294 

33 

1.922 

65 

3.623 

14 

1.319 

34 

1.961 

70 

4.000 

15 

1.346 

35 

2.000 

75 

4.416 

16 

1.373 

36 

2.040 

80 

4.875 

17 

1.400 

37 

2.081 

85 

5.383 

18 

1.428 

38 

2.122 

90 

5.943 

19 

1.457 

39 

2.165 

95 

6.562 

20 

1.486 

40 

2.208 

100 

7.245 

Interest  3  per  cent. 


1 

$1.030 

21 

$1.860 

41 

$3.360 

2 

.061 

22 

1.916 

42 

3.461 

3 

.093 

23 

1.974 

43 

3.565 

4 

.126 

24 

2.033 

44 

3.671 

5 

.159 

25 

2.094 

45 

3782 

6 

.194 

26 

2.157 

46 

•   3.895 

7 

.230 

27 

2.221 

47 

4.012 

8 

.267 

28 

2.288 

48 

4.132 

9 

.305 

29 

2.357 

49 

4.256 

10 

.344 

30 

2.427 

50 

4384 

11 

.384 

31 

2.500 

55 

5/082 

12 

1.426 

32 

2.575 

60 

5.892 

13 

1.469 

33 

2.652 

65 

6.830 

14 

1.513 

34 

2.732 

70 

7.918 

15 

1.558 

35 

2.814 

75 

9.179 

16 

1.605 

36 

2.898 

80 

10.641 

17 

1.653 

37 

2.985 

85 

12.336 

18 

1.702 

38 

3.075 

90 

14.300 

19 

1.754 

39 

3.167 

95 

16.578 

20 

1.806 

40 

3.262 

100 

19.219 

MISCELLANEOUS    NOTES. 


801 


VALUE  OF  (1  -f-  r)n.    (Continued.) 
Interest  3£  per  cent. 


Years. 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

11.035 

21 

$2.059 

41 

$4.098 

2 

1.071 

22 

2.132 

42 

4.241 

3 

1,109 

23 

2.206 

43 

4.390 

4 

1.148 

24 

2.283 

44 

4.543 

5 

1.188 

25 

2.363 

45 

4.702 

6 

1.229 

26 

2.446 

46 

4.867 

7 

1.272 

27 

2.532 

47 

5.037 

8 

1.317 

28 

2.620 

48 

5.214 

9 

1.363 

29 

2.712 

49 

5.396 

10 

1.411 

30 

2.807 

50 

5.585 

11 

1.460 

31 

2.905 

55 

6.633 

12 

1.511 

32 

3.007 

60 

7.878 

13 

1.564 

33 

3.112 

65 

9.357 

14 

1.619 

34 

3.221 

70 

11.113 

15 

1.675 

35 

3.334 

•75 

13.199 

16 

1.734 

36 

3.450 

80 

15.676 

17 

1.795 

37 

3.571 

85 

18.618 

18 

1.857 

38 

3.696 

90 

22.112 

19 

1.923 

39 

3.825 

95 

26.262 

20 

1.990 

40 

3.959 

100 

31.191 

Interest  4  per  cent. 


1 

$1.040 

21 

$2.279 

41 

$4.993 

2 

1.082 

22 

2.370 

42 

5.193 

3 

1.125 

23 

2.465 

43 

5.400 

4 

1.170 

24 

2.563 

44 

5.617 

5 

1.217 

25 

2.666 

45 

5.841 

6 

.265 

26 

2.772 

46 

6.075 

7 

.316 

27 

2.883 

47 

6.318 

8 

.369 

28 

2.999 

48 

6.571 

9 

.423 

29 

3.119 

49 

6.833 

10 

.480 

30 

3.243 

50 

7.107 

11 

.539 

31 

3.373 

55 

8.646 

12 

.601 

32 

3.508 

60 

10.520 

13 

.665 

33 

3.648 

65 

12.799 

14 

.732 

34 

3.794 

70 

15.572 

15 

.801 

35 

3.946 

75 

18.945 

16 

.873 

36 

4.104 

80 

23.050 

17 

.948 

37 

4.268 

85 

28.044 

18 

2.026 

38 

4.439 

90 

34.119 

19 

2.107 

39 

4.616 

95 

41.511 

20 

2.191 

40 

4.801 

100 

50.505 

802 


HIGHWAY    CONSTRUCTION. 


VALUE  OF  (!+»•)».    (Continued.) 
Interest  4£  per  cent. 


Years. 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

$1.045 

21 

$2.520 

41 

$6.078 

2 

1.092 

22 

2.634 

42 

6.352 

3 

1.141 

23 

2.752 

43 

6.637 

4 

1.193 

24 

2.876 

44 

6.936 

5 

1.246 

25 

3.005 

45 

7.248 

6 

1.302 

26 

3.141 

46 

7.574 

7 

1.361 

27 

3.282 

47 

7.915 

8 

1.422 

28 

3.430 

48 

8.271 

9 

1.486 

29 

3.584 

49 

8.644 

10 

1.553 

30 

3.745 

50 

9.033 

11 

1.623 

31 

3.914 

55 

11.256 

12 

1.696 

32 

4.090 

60 

14.027 

13 

1.772 

33 

4.274 

65 

17.481 

14 

1.852 

34 

4.466 

70 

21.784 

15 

1.935 

35 

4.667 

75 

27.147 

16 

2.022 

36 

4.877 

80 

33.830 

17 

2.113 

37 

5.097. 

85 

42.158 

18 

2.208 

38 

5.326 

90 

52.537 

19 

2.308 

39 

5.566 

95 

65.471 

20 

2.412 

40 

5.816 

100 

81.589 

Interest  5  per  cent. 


1 

$1.050 

21 

$2.786 

41 

$7.392 

2 

1.103 

22 

2.925 

42 

7.762 

3 

1.158 

23 

3.072 

43 

8.150 

4 

1.216 

24 

3.225 

44 

8.557 

5 

1.276 

25 

3.386 

45 

8.985 

6 

1.340 

26 

3.556 

46 

9434 

7 

1.407 

27 

3.733 

47 

9.906 

8 

1.477 

28 

3.920 

48 

10.401 

9 

1.551 

29 

4.116 

49 

10.921 

10 

1.629   . 

30 

4.322 

50 

11.467 

11 

1.710 

31 

4.538 

55 

14.636 

12 

1.796 

32 

4.765 

60 

18.679 

13 

1.886 

33 

5.003 

65 

23.84C 

14 

1.980 

34 

5.253 

70 

30.42C 

15 

2.079 

35 

5.516 

75 

38.83P- 

16 

2.183 

36 

5.792 

80 

49.56. 

17 

2.292 

37 

6.081 

85 

63.254 

18 

2.407 

38 

6.385 

90 

80.730 

19 

2527 

39 

6.705 

95 

103.035 

20 

2.653 

40 

7.040 

100 

131.501 

MISCELLANEOUS   NOTES. 


803 


VALUE  OP  (1  -f  /-)w.     (Continued.) 
Interest  6  per  cent. 


Years. 

Value. 

Years. 

1 

11.060 

21 

2 

1.124 

22 

3 

1.191 

23 

4 

1.262 

24 

5 

1.888 

25 

6 

1.419 

26 

7 

1.504 

27 

8 

1.594 

28 

9 

1.689 

29 

10 

1.791 

30 

11 

1.898 

31 

12 

2.012 

32 

13 

2.133 

33 

14 

2.261 

34 

15 

2.397 

35 

16 

2.540 

36 

17 

2.693 

37 

18 

2.854 

38 

19 

3.026 

39 

20 

3.207 

40 

Value. 

Years. 

Value. 

$3.400 

41 

$10.903 

3.604 

42 

11.557 

8.820 

43 

12.250 

4.0-19 

44 

12.985 

4.292                45 

13.7H5 

4.549                4»> 

14  590 

4  ^22                47 

15.466 

5.112                48 

16.894 

5-118                 49 

17.378 

5.743                50 

18.420 

6  088 

55 

24.650 

6453                60 

32.988 

6841 

65 

44.145- 

7.251 

70 

59.07ft 

7.686 

75 

79  057 

8.147 

80 

105.796- 

8.636 

85 

141.579- 

9  154 

90 

189465- 

9.704 

95 

253.546 

10.286 

100 

339.802. 

VALUE  OF  - — 


TABLE   XC. 

— ,  OK  THE  SINKING  FUND  THAT  WITH  COMPOUND  INTER- 


EST  WILL  AMOUNT  TO  ONE  DoLLAK  AT  THE  END  OF  A  TERM  OF  YEAHS. 

Interest  3  per  cent. 


Years. 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

$1.0000 

21 

$0.0849 

41 

$0.0127 

2 

.4926 

22 

.0827 

42 

.012-3 

8 

.8285 

28 

.0308 

43 

.0117 

4 

.2890 

24        .0290 

44 

.0112 

5 

.1884 

25        .0274 

45 

.0108 

6 

.1546 

26 

.0259 

46 

.0104 

7 

.1305 

27 

.0246 

47 

.0100 

8 

.1125 

28 

.0233 

48 

.009»i 

9 

.0984 

29        .0221 

49 

.0092 

10        .0872 

80        .02  0 

50 

.0089 

11 

.0781 

31        .0200 

55 

.0073 

12 

.0705 

32        .0190 

60 

.0061 

13 

.0640 

33 

.0182 

65 

.0051 

14 

.0585 

34 

.0178 

70 

.0048 

15 

.0538 

35 

.0165 

75        .0037 

16 

.0496 

36 

.0158 

80        .0081 

17 

.0460 

37 

.0151 

85        .0026 

18 

.0427 

38 

.0145 

90        .0028 

19 

.0398 

39 

.0138 

95        .0019 

20 

.0372 

40 

.0133 

100 

.0016 

804 


HIGHWAY   CONSTRUCTION. 


VALUE  OF 


:.     (Continued.) 


Interest  3£  per  cent. 


Years.  • 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

$1.0000 

21 

$0.0330 

41 

$0.0113 

2 

.4914 

22 

.0309 

42 

.0108 

3 

.3219 

23 

.0290 

43 

.0103 

4 

.2373 

24 

.0273 

44 

.0099 

5 

.1865 

25 

.0257 

45 

.0095 

6 

.1527 

26 

.0242 

46 

.0091 

7 

.1285 

27 

.0229 

47 

.0087 

8 

.1105 

28 

.0216 

48 

.0083 

9 

.0964 

29 

.0204 

49 

.0080 

10 

.0852 

30 

.0194 

50 

.0076 

11 

.0761 

31 

.0184 

55 

.0062 

12 

.0685 

32 

.0174 

60 

.0051 

13 

.0621 

33 

.0166 

65 

.0042 

14 

.0566 

34 

.0158 

70 

.0035 

15 

.0518 

35 

.0150 

75 

.0029 

16 

.0477 

36 

.0143 

80 

.0024 

17 

.0440 

37 

.0136 

85 

.0020 

18 

.0408 

38 

.0130 

90 

.0017 

19 

.0379 

39 

.0124 

95 

.0014 

20 

.0354 

40 

.0118 

100 

.0012 

Interest  4  per  cent. 


1 

$1.0000 

21 

$0.0313 

41 

$0.0100 

2 

.4902 

22 

.0292 

42 

.0095 

3 

.3204 

23 

.0273 

43 

.0091 

4 

.2255 

24 

.0256 

44 

.0087 

5 

.1846 

25 

.0240 

45 

.0083 

6 

.1508 

26 

.0226 

46 

.0079 

7 

.1266 

27 

.0212 

47 

.0075 

8 

.1085 

28 

.0200 

48 

.0072 

9 

.0945 

29 

.0189 

49 

.0069 

10 

.0833 

30 

.0178 

50 

0066 

11  . 

.0742 

31 

.0169 

55 

.0052 

12 

.0666 

32 

.0160 

60 

.0042 

13 

.0604 

33 

.0151 

65 

.0034 

14 

.0547 

34 

.0148 

70 

.0027 

15 

.0499 

35 

.0136 

75 

.0022 

16 

.0458 

36 

.0129 

80 

.0018 

17 

.0422 

37 

.0122 

85 

.0015 

18 

.0390 

38 

.0116 

90 

.0012 

19 

.0361 

39 

.0111 

95 

.0010 

20 

.0336 

40 

.0105 

100 

.0008 

MISCELLANEOUS  NOTES. 


805 


VALUE  OF  _    .    (Continued.) 

Interest  5  per  cent. 


Years. 

Value. 

Years. 

Value. 

Years. 

Value. 

1 

$1.0000 

21 

$0.0280 

41     $0.0078 

2 

.4878 

22 

.0260 

42  1     .0074 

3 

.3172 

23 

.0241 

43 

.0070 

4 

.2320 

24 

.0225 

44 

.0066 

5 

.1810 

25 

.0210 

45 

.0063 

6 

.1470 

26 

.0196 

46 

.0059 

7 

.1228 

27 

.0183 

47 

.0056 

8 

.1047 

28 

.0171 

48 

.0053 

9 

.0907 

29 

.0160 

49 

.0050 

10 

.0795 

30 

.0151 

50 

.0048 

11 

.0704 

31 

.0141 

55 

.0037 

12 

.0628 

32 

.0133 

60 

.0028 

13 

.0565 

33 

.0125 

65 

.0022 

14 

.0510 

34 

.0118 

70 

.0017 

15 

.0463 

35 

.0111 

75 

.0013 

16 

.0423 

36 

.0104 

80 

.0010 

17 

.0387 

37 

.0098 

85 

.0008 

18 

.0355 

38 

.0093 

90 

.0006 

19 

.0327 

39 

.0088 

95 

.0005 

20 

.0302 

40 

.0083 

100 

.0004 

Interest  6  per  cent. 


1 

$1.0000 

21 

$0.0250 

41 

$0.0061 

2 

.4854 

22 

.0230 

42 

.0057 

3 

.3141 

23 

.0213 

43 

.0053 

4 

.2286 

24 

.0197 

44 

.0050 

5 

.1774 

25 

.0182 

45 

.0047 

6 

.1434 

26 

.0169 

46 

.0044 

7 

.1191 

27 

.0157 

47 

.0041 

8 

.1010 

28 

.0146 

48 

.0039 

9 

.0870 

29 

.0136 

49 

.0037 

10 

.0759 

30 

.0126 

50 

.0034 

11 

.0668 

31 

.0118 

55 

.0025 

12 

.0593 

32 

.0110 

60 

.0019 

13 

.0530 

33 

.0103 

65 

.0014 

14  , 

.0476 

34 

.0096 

70 

.0010 

15 

.0430 

35 

.0090 

75 

.0008 

16  , 

.0390 

36 

.0084 

80 

.0006 

17 

.0354 

37 

.0079 

85 

.0004 

18 

.0324 

38 

.0074 

90 

.0003 

19 

.0296 

39 

•    .0069 

95 

.0002 

20 

.0272 

40 

.0065 

100 

.0002 

806  HIGHWAY    CONSTRUCTION. 

1046.  Sinking  Funds. — Table  XC  may  also  be  used  for  ascer- 
taining the  annual  payment  required  to  be  made  to  a  sinking  fund 
which  invested  at  compound  interest  will  yield  at  the  end  of   a 
given  period  a  sum  of  money  sufficient  to  pay  off  a  bond  issue  or 
other  debt. 

1047.  Annual  Cost  of  Pavements. — The  annual   cost  of  pave- 
ments may  be  ascertained  by  the  same  formula  as  given  in  Art. 
1045,  viz., 


x  =  ar  -\-  c  -j-  (a  —  It]  . 

in  which  a  =  first  cost; 

?•  =  rate  of  annual  interest; 
c  =  cost  of  annual  repairs; 
b  =  value  of  old  material; 
n  =  estimated  life; 
x  =  total  annual  cost. 

The  value  of  the  expression  ,        .\n  — i  *s  giyen  in  Table  XO. 

A  s  an  example  of  the  application  of  the  formula  let 
a  =  $2.00; 

r  =  3^; 
c  =  $0.03; 
b  =  $0.50; 
?i •  =  15  years. 

Then  will  x  =  ($2.00  X  .03)  =  .0600  +   .03  -f  ($1.50   X  .0538) 

—  .0807  =  $0.1707  cents  per  annum. 

The  economic  limit  of  repairs  may  also  be  ascertained  by  the 
application  of  the  above  formula. 

1048.  Relative  Economy  of  Materials. — The  material  which  has 
cost  the  most  is  not  always  the  best,  nor  is  that  which  has  cost  the 
least  the  cheapest;  the  one  which  is  truly  the  cheapest  is  the  one 
which  makes  the  most  profitable  returns  in  proportion  to  the 
amount  which  has  been  expended  upon  it.  To  make  the  most 


MISCELLANEOUS    NOTES.  807 

economical  selection  from  several  samples  of  the  same  material 
the  relative  cheapness  and  quality  of  each  must  be  ascertained. 

The  relative  cheapness  is  found  by  dividing  the  lowest  price  by 
eacli  of  the  others  in  succession  and  subtracting  the  quotient  from 
100  per  cent  taken  as  the  standard. 

The  quality  must  first  be  determined  by  the  special  tests  adapted 
to  the  material  under  consideration.  The  relative  quality  of  each 
sample  is  then  ascertained  by  dividing  the  quality  of  each  by  the 
maximum  quality  so  found  and  subtracting  the  quotient  from  100 
per  cent  taken  as  the  standard;  then  the  relative  value  is  found  by 
multiplying  the  two  ratios,  price  and  quality,  and  the  highest  prod- 
uct will  indicate  the  most  economical.  For  example,  three  prices 
are  submitted  for  a  certain  material  which,  examined  in  the  manner 
described,  shows  the  following  results: 

Price.        Relative  Cheapness  100.00.      Relative  Quality  100.00.      Relative  Economy  = 
Ratio.  Ratio.  quality  X  cheapness. 

$2.00  100.00  65.41  65.41 

2.40  99.13  100.00  99.13 

2.80  99.29  86.25  85.60 


APPENDIX. 

I. 

NAMING  AND  NUMBERING  COUNTRY  ROADS  AND  HOUSES. 

1.  THE  naming  of  country  roads  and  the  numbering  of  country 
houses  has  not  generally  received  that  recognition  which  its  impor- 
tance demands  ;  consequently  commercial  and  social  intercourse  in 
rural  sections  is  rendered  extremely  inconvenient.     The  indiffer- 
ence of  rural  communities  on  this  subject  has  been  due  to  several 
causes,  but  mainly  to  the  want  of  a  system  which  was  applicable  to. 
all  localities,  and  which  should,  without  serious  complication,  be 
sufficiently  elastic  to  cover  the  changes  wrought  by  improvement. 
Such  a  system  is  now  available.     It  is  known  as  the  "  Ten-block 
Method,"  devised  by  Mr.  A.  L.  Bancroft,  and  now  in  successful  use. 
in  Contra  Costa  County,  Cal. 

2.  The  Ten-block  System. — In  this  system  the  roads  are  first 
named  in  as  long  lengths  as  possible  (names  of  towns  or  living 
residents  are  not  used, — some  landscape  feature  or  historical  asso- 
ciation suggesting  the  name)  and  then  carefully  measured.     The 
point  from  which  the  measurements  of  all  roads  within  the  county 
are  commenced  is  the  centre  of  the  roadway  directly  in  front  of  the 
main  entrance  to  the  county  court-house ;  each  mile  is  divided  into 
10  blocks  of  528  feet,  and  each  block  is  numbered,  the  even  num- 
bers being  placed  on  the  right-hand  side  and  the  odd  ones  on  the 
left-hand  side  going  from  the  court-house;  the  block  numbers  are 
conspicuously  marked  on  the  fences  or  on  posts  specially  placed  for 
the  purpose;  a  line  indicating  the  division  of  the  block  is  placed 
between  the  numbers  thus,  52  |  50;  the  end  of  each  mile  is  indi- 
cated by  an  X  painted  inside  a  circle,  the  half-mile  is  marked  by  a 
V  in  a  semicircle;  the  houses  in  each  block  have  the  same  numbers 
as  the  block  on  which  they  stand,  but  are  distinguished  by  a  letter 
of  the  alphabet  affixed  thereto,  as  3A,  3B,  to  3Z ;  thus  when  new 

808 


APPENDIX.  809 


houses  are  built  in  the  block  they  can  have  numbers  assigned  to 
them  without  interfering  with  those  already  numbered ;  the  num- 
ber of  roads  entering  or  intersecting  a  given  road  makes  no  differ- 
ence with  the  length  or  number  of  the  block;  in  passing  through 
villages  or  towns  the  names  and  numbers  already  in  use  are  left 
unchanged,  but  outside  the  town  limits  the  ten-block  system  is 
resumed,  the  first  house  having  a  number  depending  upon  its  dis- 
tance from  the  court-house.  In  this  way,  although  a  road  passes 
through  a  dozen  towns,  the  numbers  on  each  side  of  the  town 
indicate  the  true  position  of  the  house  and  its  distance  from  the 
commencement  of  the  road.  The  distance  from  the  court-house  or 
between  any  two  given  houses  is  quickly  ascertained  by  dividing 
half  the  even  numbers  by  10 ;  for  instances,  if  a  house  is  numbered 

506,  its  distance  from  the  county  court-house  is =  — -  =  25T%- 

/o  1U 

miles,  or  the  distance  of  the  same  house  beyond  another  house 

506       315       253-157  .. 

numbered  315  is  equal  to  — —  = — =  9T67   miles, 

a  &  1U 

and  on  the  opposite  side  of  the  road. 

3.  The  data  necessary  to  put  this  system  in  operation  are  con- 
tained in  the  following  ordinance  of  the  Board  of  Supervisors  of  the 
county  of  Contra  Costa,  Cal. : 

An  ordinance  of  the  Board  of  Supervisors  of  the  county  of  Contra 
Costa,  State  of  California,  naming  the  several  public  highways 
of  the  county  and  authorizing  the  use  of  certain  other  names 
and  designations  for  private  or  local  roads  in  use  in  said 
county;  also  providing  for  the  erection  and  due  preservation 
of  suitable  guide-hoards  at  all  road  crossings  and  intersec- 
tions, and  at  other  necessary  or  suitable  points  upon  sucli 
roads  as  have  been  properly  measured  or  divided  into  blocks, 
according  to  the  "  Ten-Nock  System"  also  providing  for  the 
affixing  and  maintaining  by  residents  of  house  or  farm-entrance 
numbers,  based  thereon,  for  all  country  residences  upon  such 
measured  roads;  also  providing  for  an  official  road  map  of  the 
county,  and  other  records. 

The  Board  of  Supervisors  of  the  County  of  Contra  Costa  do 
ordain  as  follows  : 

SECTION  1.  All  public  highways  which  have  been  duly  accepted 


810  APPENDIX. 


by  the  county  shall  hereafter  be  known  and  designated  by  the 
names  prescribed  in  this  ordinance,  according  to  the  designation 
and  descriptions  laid  down  in  Section  29. 

SEC.  2.  All  private  or  local  roads  designated  in  Sec.  29  of  this 
ordinance  shall  in  all  official  reference  thereto  be  hereafter  known 
by  the  names  herein  prescribed,  and  the  public  use  and  recognition 
of  such  designation  is  hereby  recommended. 

SEC.  3.  Whenever  the  owner  or  owners  of  any  strip  or  strips  of 
land  within  the  county  shall  represent  to  the  Board  of  Supervisors 
their  purpose  and  wish  to  devote  the  same  to  use  as  a  public  or 
private  road,  or  as  a  right  of  way  for  access  to  any  dwelling,  and 
shall  offer  or  accept  a  name  for  the  same,  approved  by  the  road 
committee,  to  be  appointed  or  confirmed  .by  the  Board  of  Super- 
visors, and  shall  comply  with  the  provisions  of  the  law  respecting 
roads,  such  road  name  shall,  when  approved  by  the  Board  of 
Supervisors,  be  thereafter  used  in  all  official  reference  to  the  same, 
and  its  public  use  shall  be  recommended.  Such  road  shall  then  be 
listed  in  the  road  list  and  given  a  designating  number  and  letter 
immediately  following  the  number  of  the  road  to  which  it  is  adja- 
cent or  tributary,  until  such  time  as  the  Board  of  Supervisors  shall 
revise  the  list  and  renumber  the  roads.  And  such  road  shall 
thereafter  come  under  the  provisions  of  this  ordinance  the  same  as 
the  r.oads  enumerated. 

SEC.  4.  The  streets  of  all  unincorporated  towns  or  villages  in 
the  county  may  come  within  the  provisions  of  this  ordinance  and 
be  named.  When  numbered,  the  numbers  to  be  according  to  the 
town  method  of  100  numbers  to  the  actual  block  or  square. 

SEC.  5.  The  authorities  of  the  village,  town,  or.  city  incorpora- 
tions in  the  county  are  recommended  and  urged  to  name  the 
streets  within  their  corporate  limits,  and  to  cause  the  houses 
thereon  to  be  numbered  ;  also,  to  make  use  of  one  of  the  following 
designations  only  for  the  roadways  within  such  incorporation,  viz. : 
Alley,  Avenue,  Boulevard,  Court,  Park,  Place,  Plaza,  Promenade, 
Row,  Square,  Street,  Terrace. 

SEC.  6.  Road  measuring  and  numbering,  as  contemplated  by  this 
ordinance,  are  hereby  defined  and  described  as  follows  :  All  roads 
shall  be  measured  along  the  surface  line  of  the  same,  as  near  to 
the  middle  of  the  roadway  as  practicable,  and. laid  off  in  imaginary 
blocks  one  tenth  of  a  mile,  or  528  feet  frontage  each,  according  to 


APPENDIX.  811 


the  "  Ten-block  System  of  Numbering  Country  Houses."  A  line 
to  indicate  the  division  between  these  blocks,  with  the  block  num- 
ber on  either  side  of  the  same,  shall  be  marked  or  painted  upon  the 
fence  where  practicable,  and  where  it  exists  in  a  fair  state  of  pres- 
ervation, or  upon  any  other  permanent  object  on  one  or  both  sides 
of  the  road.  The  odd  numbers  shall  be  applied  to  the  blocks  on 
the  left-hand  side  of  the  road,  and  the  even  numbers  to  the  right- 
hand  side.  The  block  numbers  shall  be  in  figures  not  less  than 
two  inches  nor  more  than  two  and  one  half  inches  in  height  where 
the  fence  board  or  other  object  will  admit  of  this  size,  and  so 
plainly  painted  as  to  be  easily  read  from  the  centre  of  the  road. 
The  mile  distances  shall  be  distinguished  in  some  suitable  manner, 
as  by  a  full  circle,  and  the  half-mile  by  a  half  circle  or  other  suit- 
able device. 

SEC.  7.  The  initial  point  of  measuring  for  roads  leading  from  the 
county  seat  shall  be  the  centre  of  the  street  immediately  in  front 
of  the  main  entrance  to  the  court-house  at  Martinez.  Other  roads 
shall  be  measured  at  the  end  nearest  the  county  seat,  and  branch 
roads  the  same,  or  from  the  main  road  to  which  they  are  tributary. 

SEC.  8.  Note  shall  also  be  taken  and  a  record  kept  of  the  block 
within  which  is  located,  and  the  number  of  feet  in  or  within  the 
block  (i.  e.,  the  distance  from  the  commencement  of  the  block),  of 
all  bridges,  large  culverts,  important  permanent  springs,  drinking 
troughs,  public  monuments,  summits,  road  crossings  and  intersec- 
tions and  objects  of  special  prominence,  and  the  correct  block  num- 
ber be  marked  thereon,  or  near  thereto,  where  practicable. 

SEC.  9.  Note  shall  also  be  made  and  a  record  be  kept  of  the 
number  of  the  block  within  which  is  located,  and  the  number  of  feet 
in  or  within  the  block,  of  each  and  every  house  entrance  or  gate- 
way, lane,  or  road  leading  from  the  highway  to  any  residence  upon 
the  roads,  or  to  which  access  is  had  by  way  of  the  road,  with  the 
name  or  names  of  the  owner  or  occupant,  when  practicable  to  pro- 
cure them ;  also,  to  the  entrance  to  all  school-houses,  churches,  and 
public  buildings. 

SEC.  10.  The  measurement  of  all  roads  which  pass  through  or 
enter  the  corporate  limits  of  cities  or  towns  shall  be  continuous, 
regardless  of  such  boundaries  ;  but  the  block  and  country-house 
numbers  may  be  omitted  within  such  corporations. 

SEC.  11.  In  the   measurement  of  the   roads  of  the  county  re- 


812  APPENDIX. 


quired  by  this  ordinance  a  record  shall  be  made  and  preserved 
of  the  general  course  of  bearings  by  the  compass  of  all  roads  at 
road  crossings  or  intersections;  also,  the  general  course  of  all  private 
or  local  roads  at  their  point  of  departure  from  the  main  road ;  and 
it  shall  be  the  duty  of  the  county  surveyor  to  prepare  and  place  on 
file,  in  the  office  of  the  clerk  of  the  county,  a  complete  road  map 
of  the  county,  with  the  names  of  all  roads,  and,  whenever  the  same 
are  measured,  the  block  numbers  at  their  commencement  at  all 
roads,  crossings,  and  at  all  crossings  and  connections  of  all  roads, 
and  at  their  endings,  together  with  the  boundaries  of  the  several 
road  districts  in  the  county. 

SEC.  12.  The  measurement  of  the  roads  of  the  county  may  in- 
clude the  record  of  the  accurate  reading  by  barometer  of  the  alti- 
tudes or  elevations  above  the  sea-level  of  the  commencement  and 
ending  of  all  roads,  all  plains,  valleys,  the  foot  and  summit  of  hills 
and  the  slopes  of  mountains,  at  suitable  distances.  The  records  of 
such  altitudes,  if  taken,  to  be  placed  over  the  block  number  nearest 
the  point  of  observation,  or  otherwise  suitably  posted,  to  show  the 
range  of  important  elevations  traversed. 

SEC.  13.  Whenever  one  or  more  residents  or  owners,  upon  any 
road  enumerated  in  section  29,  or  hereafter  designated  and 
described,  as  required  by  this  ordinance,  or  other  person,  shall 
furnish  the  Board  of  Supervisors  satisfactory  evidence  that  the 
provisions  of  this  ordinance,  respecting  road  measuring  and  number- 
ing, have  been  faithfully  complied  with  upon  any  road  touching  the 
county  seat,  or  upon  any  road  connecting  with  any  other  road 
which  has  been  previously  measured  and  blocked  off;  and  when- 
ever such  residents  shall  file  with  the  county  clerk  the  record 
required  in  sections  8,  9,  and  11 ;  and  whenever  such  resident,  resi- 
dents, or  other  persons  shall  have  affixed  block  numbers  at  the  be- 
ginning and  ending  of  such  roads,  and  at  each  mile  and  half-mile 
division  thereof,  where  practicable  or  oftener, — then,  and  in  that 
case,  it  shall  be  the  duty  of  the  Board  of  Supervisors  to  erect  upon 
such  road,  or  roads,  guide-boards,  as  hereinafter  prescribed. 

SEC.  14.  Whenever  any  such  road  is  so  measured  and  block  num- 
bers designated  thereon,  thenceforth  and  thereafter  the  several 
requirements  of  this  ordinance  as  to  the  maintenance  of  house 
numbers,  the  protection  and  preservation  of  guide-boards,  etc., 


APPENDIX. 


813 


shall  become  applicable  and  in  force  along  and  upon  such,  road,  or 
roads,  and  the  penalties  herein  prescribed  shall  be  duly  enforced. 

SEC.  15.  The  guide-boards,  when  ordered  upon  any  road,  shall 
be  erected  and  permanently  maintained  at  the  following-named 
points,  and  at  such  places  as  the  Board  of  Supervisors  may  here- 
after prescribe:  At  or  near  the  commencement  of  all  roads  or 
branch  roads,  at  all  road  crossings  or  intersections,  at  all  ferry 
landings,  at  all  railroad  stations,  and  at  all  crossings  of  the  county 
boundary.  They  shall  be  so  placed  on  the  principal  roads  as  to 
face  the  traveller  when  moving  from  the  county  seat. 

SEC.  16.  Such  guide-boards  shall  be  of  iron,  not  less  than  No.  16 
in  thickness,  galvanized  and  painted.  They  shall  be  at  right  angles 
to  fit  the  post,  and  with  two  arms  or  boards  for  the  lettering.  The 
outer  edges  shall  be  bent  back  from  the  face  one  half  inch  in 
width,  the  lower  portion  being  cut  away  the  width  of  the  post,  and 
the  upper  lip  to  rest  on  top  of  the  post,  to  which  the  board  must 
be  securely  atttached  by  a  sufficient  number  of  screws.  The  posts 


G-RANVILLE    WAY 
From  2IIC.C.H/GWAYT086  YlSTA  /ONACIA  $£N& 

* —  CONCORD  10.5  M 

CLAYTON  16.2  M 

— >  LAFAYETTE:  s.e  M 

OAKLAND  12.9  M 

ELEV.  96ft 


op 


od  GI/IDE.  BO/\RDj> 


shall  be  of  sound  redwood,  6x6  inches,  and  twelve  feet  long,  to  be 
set  three  feet  in  the  ground,  with  cross-pieces  nailed  to  the  post,  in 
light  soils.  The  top  and  the  portion  below  the  ground  to  be  in  or 
painted  with  coal-tar,  or  some  other  wood  preservative,  the  por- 
tion above  the  ground  to  be  painted  with  two  coats  of  good  metal- 
lic or  other  suitable  paint.  The  exposed  surface  of  the  boards 


S14  APPENDIX. 


shall  be  15  x  24  inches  in  size,  each,  except  at  the  entrance  to  local 
roads,  which  may  have  but  a  single  projecting  arm  6x15  inches  in 
size  and  affixed  to  a  4  X  4  inch  post ;  in  all  other  particulars  to  be 
of  similar  construction  to  the  larger  size;  the  wording  and  lettering 
to  conform  to  the  general  plan  indicated  by  the  design  accompanying 
this  ordinance,  and  made  a  part  thereof.  All  of  the  lettering  upon 
the  guide-boards,  except  the  second  line,  which  is  in  letters  smaller 
than  the  others,  and  a  section  of  eighteen  inches  of  the  two  faces 
of  the  guide-post  directly  under  the  guide-board,  shall  be  painted 
with  luminous  paint. 

SEC.  17.  Upon  all  guide-posts  the  following  notice  shall  be  con- 
spicuously painted  or  stencilled: 

A  PENALTY  FOK  DEFACING  OR  POSTING. 

SEC.  18.  Whenever  the  provisions  of  section  13  have  been  com- 
plied with  as  to  road  or  roads,  and  guide-boards  have  been  erected, 
the  supervisors  shall  also  cause  a  printed  notice  to  be  served  upon 
the  occupants  of  every  residence  upon  such  road  or  roads  outside 
the  limits  of  incorporated  towns,  left  at  such  residence,  or,  where 
the  residence  is  distant  a  mile  or  more  from  the  public  or  named 
roads,  mailed  to  their  address,  accompanied  by  a  copy  of  tins 
ordinance  or  abstract  thereof.  Such  notice  shall  also  be  delivered 
or  mailed  to  one  of  the  officers  of  each  school  district  and  church  of 
which  the  building  is  located  upon  said  measured  road.  These 
notices  shall  have  a  blank  form,  to  be  properly  filled  with  the  exact 
location  and  correct  number  of  the  entrance  to  the  house,  with 
instructions  as  to  the  house  number  to  be  posted  and  maintained. 

SEC.  19.  Every  householder  upon  such  measured  road,  residing 
outside  the  limits  of  incorporated  towns,  shall,  within  thirty  days 
after  the  service  of  the  notice  required  in  section  18,  post,  and 
thereafter  permanently  maintain  in  legible  condition,  upon  the 
road  or  at  the  entrance  or  right  of  way  from  the  road,  the  correct 
house  number  of  his  residence  as  given  in  said  notice.  It  shall  be 
placed  in  such  a  conspicuous  position  as  to  be  easily  seen  and  read 
from  the  centre  or  opposite  side  of  the  road.  The  figures  shall  be 
well  proportioned,  and  of  a  size  not  less  than  three  inches  in  height, 
nor  more  than  four  inches,  except  in  town  or  village  settlements, 
where  the  numbers  may  be  one  inch  less  in  height,  and  may  be 
maintained  upon  the  doorway  or  at  the  gate.  The  numbers  must 


APPENDIX.  815 


be  neatly  made,  and  in  the  style  and  manner  that  a  professional 
sign-writer  would  use. 

SEC.  20.  Any  owner  or  occupant  of  any  dwelling  in  the  county 
which  is  reached  by  a  private  road  or  right  of  way  is  hereby  per- 
mitted to  post  and  maintain  his  house  number  upon  the  public 
highway  at  the  entrance  to  such  private  road  or  right  of  way,  or 
upon  such  private  road  or  right  of  way,  and  he  or  she  may  place 
therewith  his  or  her  own  name  and  business,  provided  such  sign  i^ 
made  in  a  neat  and  tasteful  manner,  and  conforms  to  the  provisions 
of  this  ordinance. 

SEC.  21.  Whenever  the  occupant  of  any  dwelling  upon  a 
measured  and  numbered  road  shall  fail  for  the  term  of  thirty 
days  to  maintain  the  proper  house  number  at  the  entrance  thereto, 
and  having  been  notified  by  the  road  officer  to  comply  with  the 
law  shall  fail  to  do  so,  he  shall  be  deemed  guilty  of  a  misdemeanor. 

SEC.  22.  Whenever  any  house  upon  a  measured  and  numbered 
road  now  vacant  shall  be  occupied,  or  any  new  dwelling-house  shall 
be  erected  upon  such  road,  it  shall  be  the  duty  of  the  occupant 
within  thirty  days  to  properly  post  and  thereafter  permanently 
maintain,  at  the  entrance  thereto,  the  correct  house  number  of  the 
3ame  as  provided  in  this  ordinance,  and  such  residence  shall  there- 
after come  under  the  provisions  of  this  ordinance  the  same  as 
dwelling  now  occupied. 

SEC.  23.  There  shall  be  prepared  for  county  use  a  book  of 
records  for  the  roads  of  the  county,  in  which  shall  appear,  arranged 
in  proper  order,  under  the  name  of  each  road,  an  index  of  all 
ordinances  or  other  official  action  relating  to  that  road,  making 
such  road  record  an  official  history  of  all  the  roads  of  the  county. 

SEC.  24.  A  copy  of  all  the  field  notes  of  the  survey  measure- 
ments, elevations,  and  other  records,  with  the  block  and  house 
numbers  as  provided  for,  shall  be  carefully  preserved  in  the  office 
of  the  county  clerk,  and  open  to  the  inspection  of  citizens  as  are 
other  county  records. 

SEC.  25.  The  execution  of  the  work  required  by  this  ordinance 
shall  be  subject  to  the  inspection  and  be  made  to  conform  to  the 
requirements  of  a  road  committee  to  serve  without  pay,  and  to  con- 
sist of  three  members,  one  to  be  appointed  by  the  Board  of  Super- 
visors, one  to  be  named  by  the  road-naming  committee  who  have 
prepared  this  plan,  and  the  third  to  be  chosen  by  the  two  thus 


816 


APPENDIX. 


appointed,  and  all  to  be  confirmed  by  the  Board  of  Supervisors; 
and  any  work  of  measurement.,  erecting  guide-boards,  or  affixing 
numbers,  shall  not  be  held  to  be  complete  until  approved  by  a 
majority  of  this  committee. 

SEC.  26.  It  shall  be  the  duty  of  the  road  officials  to  thoroughly 
inspect  the  roads  within  their  respective  districts  and  to  make  reports 
to  the  Board  of  Supervisors  at  least  as  often  as  at  the  close  of  each 
six  months  of  their  terms  of  office,  as  to  the  condition  of  such 
roads,  and  any  failure  to  comply  with  the  provision  of  this  ordi- 
nance. They  shall  also  see  that  guide-boards  are  preserved  in  a 
legible  condition  and  house  numbers  properly  maintained,  notifying 
residents  of  any  neglect  in  this  respect.  It  shall  be  their  duty  to 
report  any  person  charged  with  violating  the  provisions  of  this  ordi- 


CONTRA   COSTA    HIGHWAY 


-£->ALAMO  S.ZM  DANVILLE     6.3M 

°      SANRAMONI0.7MDUBLIN        I5.4M 
LlVERMORE      I9.6M 

-PACHECO  5.7M  MARTINEZ  IO.GM 

ELEV,  96ft 


NO,  2.   GUIDE  BOARD   AT   RiOHT   AN<H_ES~TO  KO.l. 

nance,  and  to  enter  complaint  against  them  in  such  case ;  they  shall 
also  have  full  authority  to  arrest  any  person  or  persons  found 
defacing  or  removing  block  or  house  numbers,  or  mutilating  any 
guide-board,  or  posting  any  notice  upon  the  post  or  boards,  or  in 
any  way  violating  the  provisions  of  this  ordinance. 

SEC.  27.  If  any  person  or  persons  shall  mutilate,  deface,  destroy, 
or  remove  any  guide-board  or  guide-post,  any  block  or  house  num- 
ber, any  name,  sign,  or  advertisement  which  may  be  lawfully  posted 
at  or  upon  the  entrance  to  the  residence  or  dwelling  of  any  person 
to  whom  such  notice  belongs,  whether  such  entrance  be  public  or 
private  or  through  right  of  way,  or  shall  mar,  deface,  or  injure,  by 
shooting,  stoning,  or  otherwise,  any  guide  post  or  board,  or  shall 


APPENDIX.  817 


fasten,  or  paint,  or  stencil  any  notice  or  advertisement  to  such  posts 
or  boards,  save  such  as  are  required  by  this  ordinance,  the  person 
or  persons  so  offending  shall  be  deemed  guilty  of  misdemeanor, 
punishable,  upon  due  conviction,  by  a  fine  of  $50,  one  half  of 
which  shall  go  to  the  informer,  or  by  imprisonment,  or  both. 

SEC.  28.  The  roads  of  the  county,  as  enumerated  in  section  29, 
are  listed  according  to  the  following  rule  :  Commence  on  the 
east  side  of  a  line  extending  due  north  from  the  county  seat  and 
work  around  in  a  circle  to  the  east,  southwest,  and  back  again  to 
the  north,  always  facing  outward  and  working  from  the  county  seat 
outward,  and  always  from  the  left  to  the  right.  List  first  those 
roads  touching  the  county  seat ;  next  the  first  left-hand  branch 
roads,  and  any  left-hand  branches  of  these.  Continue  with  the 
right-hand  branches,  follow  with  the  remaining  trunk  roads  and 
their  branches,  left-hand  branches  first,  right-hand  branches 
next  ;  omitting  nothing  on  the  left  until  the  entire  circuit  has 
been  made  and  the  roads  of  the  county  are  all  listed.  Under  this 
rule  the  roads  leading  from  Martinez,  five  of  them  are  first  listed  ; 
then  the  first  of  the  five  which  have  branches,  No.  2,  and  then  con- 
tinued in  the  order  explained  above. 

SEC.  29.  The  following  are  the  names  of  several  public  high- 
ways and  private  or  local  roads  of  the  county,  respectively  hereby 
authorized  and  established.  [List  of  130  roads,  among  which  are  : 

Alpha  Way,  from  Martinez  to  BulFs  Head  ;  Contra  Costa 
Highway,  from  Martinez  to  County  line  via  Pacheco,  Walnut 
Creek,  and  San  Ramon  Valley  ;  Alhambra  Way,  from  Martinez  to 
Pinole  ;  Granville  Way,  from  Contra  Costa  Highway,  near  Wal- 
nut Creek,  to  Vista  Ignacio,  Franklin  Road  ;  Teal  Local  ;  Tule 
Road,  Pecheco  Exit,  Vine  Hill  Way  ;  Locust  Way,  Plover  Connex  ; 
Willow  Pass  Road  ;  Flunaveg  (River  Road),  Bla,ck  Diamond 
Way  ;  Empire  Road  ;  Paso  Corto  ;  Camino  Diablo,  Carbon  Way ; 
Arbor  Connex  ;  Lone  Tree  Road,  Almond  Way  ;  Summer  Road, 
Dry  Creek  Local  ;  Zigzag  Way,  Sunol  Local ;  Concord  Lateral ; 
Pomona  Road  ;  Ferndale  Local ;  Golden  Gate  Way ;  Vaca  Cres- 
cent; Verdel  Circuit  ;  Acorn  Local,  Highland  Drive  ;  and  Forest 
Road.] 

SEC.  30.  This  ordinance  shall  take  effect  and  be  in  force  on  the 
16th  day  after  its  passage. 

Passed  March  8,  1892. 


818  APPENDIX. 


II. 

METHODS   OF  ASSESSING  THE   COST  OF  STREET-PAVING. 

THE  following  summary  shows  the  different  methods  employed 
for  assessing  the  cost  of  street-paving: 

I.  THE  WHOLE  COST  BORNE  BY  THE  ABUTTING   PROPERTY;  e.g., 

Albany,  Brooklyn,  Buffalo,  New  York,  Rochester,  Syracuse,  Troy, 
N.  Y.;  Boston,  Mass.;  Newark,  Paterson,  N.  J.;  Philadelphia, 
Harrisburg,  Scran  ton,  Pa.;  Baltimore,  Md.;  Dayton,  Ohio;  In- 
dianapolis, Ind. ;  Peoria,  111.;  Milwaukee,  Wis.;  St.  Paul,  Minn.; 
San  Francisco,  Cal. ;  Kansas  City,  Mo. 

II.  THE     WHOLE    COST    BORNE     BY    THE   CITY    AT    LARGE;    e.g., 

Portland,  Me.;  Manchester,  N.  H.;  Springfield,  Mass.;  Wilming- 
ton, Del.;  Richmond,  Va. ;  Charleston,  S.  C. ;  Nashville,  Tenn. 

III.  THE    COST     DIVIDED    EQUALLY    BETWEEN    THE     ABUTTING 

PROPERTY  AND  THE  CITY;  e.g.,  Washington,  D.  C.;  Augusta,  Ga.; 
Montgomery,  Ala. 

IV.  THE  COST  DIVIDED  IN  PROPORTION  OF  TWO-THIRDS  ON  THE 

ABUTTING  PROPERTY  AND   ONE-THIRD  ON  THE   CITY;   e.g.,  OswegO, 

N.  Y. ;  Hartford,  Conn.;  Atlanta,  Ga. ;  Jacksonville,  Fla. 

V.  THE    ABUTTING    PROPERTY    PAYS    FOR    ITS    FRONTAGE,  AND 

THE  CITY  PAYS  FOR  INTERSECTIONS;  e.g.,  Allegheny,  Pa.;  Sioux 
Falls,  S.  Dak. 

VI.  THE     ABUTTING    PROPERTY   PAYS    FOR   THE    GRADING,  THE 

CITY  PAYS  FOR  THE  PAVING;  e.g.,  Lowell,  Worcester,  Mass.;  Provi- 
dence, R.  I. 

VII.  THE    CITY   PAYS   FOR  THE  GRADING    AND    ONE-THIRD    OF 
THE    PAVING,  THE  PROPERTY    PAYS    THE  REMAINING   TWO-THIRDS; 

e.g.,  Hartford,  New  Haven,  Conn.,;  Atlanta,  Ga. 

VIII.  THE    CITY    PAYS   ONE-HALF   COST   OF  GRADING  AND  ALL 
COST    OF     INTERSECTIONS,    THE  PROPERTY    PAYS   THE    REMAINDER; 

e.g.,  Salt  Lake  City,  Utah. 

IX.  THE  CITY  PAYS   FOR   ONE-HALF  THE   GRADING,  THE    ABUT- 


APPENDIX.  819 


TING  PROPERTY    THK    OTHER    HALF   AND    THE  WHOLE    COST    OF   THE 

PAVING;  e.g.,  Omaha,  Neb. 

X.  THE  CITY  PAYS  ONE-FOURTH  OF  THE  WHOLE  COST,  AND  THE 

PROPERTY  THREE-FOURTHS;  e.g.,  New  Orleans,  La. 

XI.  ClTY  PAYS  FOR  GRADING  AND  FOR  THE  PAVING  OF  STREET 

AND  ALLEY  INTERSECTIONS;  e.g.,  Detroit,  Mich. 

XII.  THE  COST  DIVIDED  BETWEEN  THE  CITY  AND  THE  PROP- 
ERTY IK  DIFFERENT  PROPORTION;  e.g.,  Cincinnati,  Ohio,  city  pays 
2$,  property  98$;   Cleveland,  0.,  city  pays  -^  and  intersections, 
property  $£. 

XIII.  THE  CITY  PAYS  FOR  GRADING;  COST  OF  PAVING  ASSESSED 

UPON   ABUTTING    PROPERTY    IN   PROPORTION   TO    BENEFIT,    DETER- 
MINED BY  APPRAISERS  SPECIALLY  APPOINTED;  e.g.,  Topeka,  Kan. 

XIV.  THE  WHOLE  COST  PAID  BY  THE  ABUTTING  PROPERTY  IN 
PROPORTION  TO  ITS  VALUE;  e.g.,  Little  Rock,  Ark. 

When  the  assessment  is  by  improvement  districts,  all  land, 
including  street  areas,  between  termini  of  the  improvements  and 
within  a  fixed  distance  (usually  one-half  the  depth  of  the  block) 
of  the  street  line  on  each  side  of  the  street  improved  constitutes 
an  improvement  district,  except  that  when  a  cross-street  has 
already  been  improved  its  area  is  excluded.  The  area  on  each 
side  of  the  street-lines  is  divided  into  zones  by  lines  drawn  parallel 
to  the  street-line.  The  number  of  the  zones  may  be  three,  four,  or 
more.  When  four  are  used  the  total  cost  is  levied  on  the  area 
within  the  zones  in  the  proportion  of  40  per  cent  on  the  one  im- 
mediately adjoining  the  street,  and  on  the  other  at  the  rate  of  25, 
20,  and  15  on  the  most  remote.  In  some  cases  the  centre  line  of 
the  street  to  be  improved  is  taken  as  the  base  for  the  zones;  in  this 
case  the  city  at  large  pays  the  assessment  charged  to  the  street 
area. 

In  all  cases  where  the  assessment  is  made  by  frontage,  the  loca- 
tion or  value  of  the  property  is  not  taken  into  account. 

In  cases  where  the  cost  is  borne  by  the  city  at  large  it  is  paid 
either  from  the  general  tax  or  by  the  emission  of  bonds  or  im- 
provement certificates. 

The  practice  of  assessing  corner  lots  varies.  In  Louisville, 
Ky.,  they  pay  25  per  cent  more  than  inside  lots.  In  Portland, 
Ore.,  the  corner  lot  is  assessed  f  and  the  one  adjoining  f . 


820  APPENDIX. 


Tlie  street-railway  companies  are  assessed  in  various  ways : 
J..  Directly  for  the  area  occupied  by  them. 

2.  Are  required  to  do  the  paving  and  maintain  the  space  be- 
tween their  rails  and  from  1-J  to  2  feet  outside  the  rails. 

3.  They  are  required  to  maintain  the  pavement  from  curb  to 
curb,  as  in  Philadelphia. 

4.  A  certain  proportion  of  the  cost  is  assessed  against  them,  as 
i  in  Brooklyn. 

Renewals  and  Repaving  are  paid  for  either  by  the  property  or 
the  city.  The  following  are  examples : 

City  pays:  Albany,  N.  Y.,  •£;  Brooklyn,  K  Y.,  -J  in  special 
cases;  New  York;  Paterson,  N.  J.;  Scranton,  Pa.,  |;  Dayton,  0,; 
Detroit,  Mich. 

Property  pays:  Albany,  N.  Y.,  -J-;  Syracuse,  N.  Y.;  Newark, 
N.  J.;  Scranton,  Pa.,  \. 


APPENDIX. 


821 


III. 

ORDINANCE  REGULATING  THE  WIDTH   OF  WAGON- TIRES. 

1.  The  owner,  driver,  or  person  for  the  time  being  employing 
or  having  the  care  or  control  of  any  wagon,  truck,  cart,  or  carriage 
drawn  by  animal  power  shall  not  cause  or  suffer  such  vehicle  to  be- 
used  on  any  road  or  highway  in  contravention  of  any  such  of  the- 
following  regulations  as  may  be  applicable  to  such  vehicle,  that  is 
to  say : 

2.  No  wagon,  truck,  cart,  or  carriage  shall  be  used  on  any  road 
of  which  the  felloes  or  tires  at  the  bottom  or  soles  of  the  wheels 
are  not  of  the  width  in  proportion  to  the  gross  weight  as  herein- 
after mentioned,  such  gross  weight  including  not  only  the  persons, 
load,  or  things  carried  by  such  vehicle,  but  also  the  weight  of  the 
vehicle  itself.     The  tires  must  be  neither  concave  nor  convex. 


Description  of  Vehicle. 


Gross  Weight,  Pounds. 

Two  Wheels. 

Four  Wheels. 

Without 
Springs. 

With 
Springs. 

Without 
Springs. 

With 
Springs. 

Width  of  Tire. 

Width  of  Tire. 

Inches. 

Inches. 

Inches. 

Inches. 

Less  than  2,000. 

2,000  and 

less  than   3,000. 

3,000     ' 

"      •       4,000. 

4,000     ' 

"      •       6,000. 

6,000     • 

41      '       8,000. 

8,000     ' 

"      '     10,000. 

10,000     ' 

"      '     12,000. 

For  the  transportation  of  loads  exceeding  6  tons  special  permits  must  be 
obtained. 

3.  The  owner,  driver,  or  person  for  the  time  being  employing 
or  having  the  care  or  control  of  any  wagon,  truck,  cart,  or  carriage 


822  APPENDIX. 


drawn  by  animal  power  on  any  road  or  highway  shall  not  cause  or 
suffer  the  wheel  of  such  vehicle  to  be  locked  when  descending  a 
hill,  except  the  hill  be  in  a  slippery  condition  from  ice  or  snow, 
unless  there  be  placed  at  the  bottom  of  such  wheel,  during  the 
whole  time  of  its  being  locked,  a  skid-pan,  slipper,  or  shoe,  in  such 
manner  as  to  prevent  the  road  from  being  destroyed  or  injured 
from  the  locking  of  such  wheel.  No  vehicle  shall,  when  descend- 
ing a  hill,  have  both  hind  wheels  locked. 

4.  No  vehicle  shall  have  any  nail  or  bolt  on  the  tire  of  any 
wheel  which  shall  not  be  countersunk  so  as  not  to  project  beyond 
one-quarter  of  an  inch  above  any  part  of  the  surface  of  the  tire  of 
such  wheel. 

5.  Th'e  driver  or  other  person  having  for  the  time  being  the 
care  or  control  of  any  wagon,  truck,  cart,  or  carriage  shall,  upon 
demand  made  to  him  by  the  county  engineer,  or  any  of  his  assist- 
ants, or  by  any  officer  duly  appointed,  empowered,  or  instructed  in 
that  behalf  by  the  county  authority  of  the  county  of 

or  by  any  police  officer,  stop  such  vehicle,  and  permit  the  person 
so  demanding  to  examine  for  a  reasonable  time  the  wheels  thereof, 
or  the  nature  and  amount  of  the  loading  thereof,  with  the  view  of 
ascertaining  whether  all  or  any  of  the  regulations  aforesaid  are 
then  being  contravened. 

6.  The  driver  or  other  person  having  for  the  time  being  the 
control  or  care  of  any  wagon,  truck,  cart,  or  carriage  shall,  upon 
demand  made  to  him  by  any  such  person  as  aforesaid,  cause  such 
vehicle,  together  with  the  loading  thereof,  to  be  driven  to  any 
weighing-machine  for  the  purpose  of  being,  and  shall  cause  or 
suffer  the  same  to  be,  weighed  thereby  or  thereon,  provided  that 
such  driver  or  person  shall  not  be  required  to  drive  or  cause  to  be 
driven  such  vehicle,  together  with  the  loading   thereof,  to  such 
weighing-machine  if  at  the  time  when  such  demand  as  aforesaid 
shall  be  made  such  vehicle  shall  be  at  a  greater  distance  than  half 
a  mile  from  such  weighing-machine. 

7.  Every  person  who  shall  break  any  of  the  regulations  of  this 
ordinance  shall  be  deemed  guilty  of  a  misdemeanor,  punishable, 
upon  due  conviction,  by  a  fine  of  $10,  or  by  imprisonment,  or  both. 

8.  This  ordinance  shall  take  effect  and  be  in  force  on  the 
day  of  ,  18     . 


APPENDIX.  823 


IV. 
CYCLE-PATHS. 

Cycle-paths  through  the  country  may  be  constructed  according 
to  the  most  elaborate  specifications  for  broken-stone  road  construc- 
tion, or  consist  simply  of  a  bed  of  gravel  or  cinders  slightly  raised 
above  the  adjoining  surface.  In  city  streets  strips  of  asphalt  or 
brick  pavement  are  the  most  suitable. 

Location. — In  the  country  the  paths  should  be  placed  at  one 
side  of  the  roadway  and  so  protected  that  wagons  cannot  use  them. 
In  city  streets  the  best  location  seems  to  be  adjoining  the  curb, 
and  there  should  be  a  path  on  each  side  of  the  street  so  the  cy- 
clists can  move  in  the  same  direction  as  the  traffic. 

Width. — Six  feet  is  the  minimum  width  to  allow  wheelmen  to 
meet  and  pass  without  danger  of  accident.  Single  paths  at  the 
side  of  streets  should  be  3  feet  wide. 

Crown. — 

Paths  3  feet  wide  should  have  a  crown  of  \\  inches. 

"      6    "       "          "          "     "      "       "  3 
««    10    „        «          ««         «.     «      «       «.  4 

"    18    "       "  "     "      "       "  6 

Grades  should  be  as  flat  as  possible. 

Drainage. — In  paths  through  the  country  attention  must  be 
paid  to  the  drainage. 

Construction. — Gravel  or  cinders  should  have  a  thickness  of  3 
inches  and  should  be  well  rolled.  The  gravel  should  pass  through 
a  -J-inch  screen.  If  a  foundation  is  required,  it  may  consist  of 
cinders  4  inches  thick,  thoroughly  rolled  and  covered  with  a  layer 
of  loamy  clay  -J  inch  thick,  moistened  and  rolled.  A  mixture  of 
sand  and  loamy  clay  in  sufficient  quantity  to  bind  the  sand  has 
given  good  results.  , 

Broken  Stone  (Brooklyn,  N.  Y.J. — Foundation  consists  of 
gravel  covered  with  a  layer  of  broken  stone  3  inches  thick,  rolled 
with  a  steam-roller  and  covered  with  stone  screenings  from  i  to  i 
inch  in  size. 


INDEX. 


63.  Abrasion  of  granite. 26 

63.  limestone 26 

63.  paving-brick ,     26 

63.  wood 26 

61,  355.         tests  of 25,  259 

64.  Absorptive  power  of  bricks  (Table  V) 27 

cement  (Table  XLIV) 336 

granite  (Table  V) 27 

limestones  (Table  V) 27 

marbles  (Table  V) 27 

64.  materials,  effect  of 2tf 

64.  mortar  (Table  V) 27 

64,  119.  paving-bricks  (Table  V  and  Table  XXI) 27,  87 

sandstones  (Table  V) 27 

64.  stones,  etc.  (Table  V) 27 

64,  121.  wood  (Table  V  and  Table  XXIII) 27,  93 

706.  Abutments  for  pipe-culverts 468 

714.  tliickness  of  (Table  LXXVI)  478 

22.  Accidents  to  horses 10 

753.  Accommodation  summits 510 

862.  Accounts 599 

617.  Acres,  number  of,  required  per  mile,  for  different  widths  of  roads 

(Table  LXIII) 417 

59,  410.  Action  of  the  weather 24,  284 

482.  Activity  of  cement ; 334 

486.  tests  for 336 

9.  Adaptability  of  pavements 4 

641 .  Adhesion  of  earth 424 

500.  Adhesive  strength  of  mortar  (Table  XLV) 344,  345 

751.  Adjustment  of  grades  at  street-intersections 507 

825 


INDEX. 


ARTICLE  PAGE 

153.  Advantage  of  sorting  granite  blocks  at  the  quarry 107 

188.  creosoting  wood 132 

511.  mixing  mortar  by  machinery 358 

221.  asphalt  pavements 159 

281.  and  coal-tar  pavements. 203 

305.  brick  pavements 219 

346.  broken-stone  pavements 250 

281.  coal-tar  and  asphalt  pavements. 203 

140.  granite-block  pavements 102 

511.  mixing  concrete  by  machinery 358 

396.  rolling  broken-stone  pavements 274 

13.  smooth  pavements 6 

398.  steam-rollers 275 

439.  stone  trackways 306 

550.  wheels 387 

177.  wood  pavements 124 

485.  Age,  effect  of,  on  cement 336 

50.1.  strength  of  mortar 350 

1030.  Agreement,  form  of 694 

584.  Alignment  of  roads 401 

1025.  Alteration  of  manhole  heads,  etc 687 

92«.  American  asphaltum 42 

99e.  bituminous  rock 51 

300.  cost  of  construction 212 

303.  pavement,  specifications  for 212 

297.  pavements 21 1 

473.  natural  cements,  colors  of 328 

473.  specific  gravity  of. 328 

103a.  Ammonia,  action  on  bitumen 65 

256.  Amount  of  aspbaltic  cement  made  by  one  ton  of  refined  asphaltum..  184 
388.  binding  material  required  for  broken-stone  pavements. . .   272 

103«.  bitumen  in  asphaltic  paving-cement 73 

bluestone  used  for  street  purposes  in  1889  (Table  XI). . .     35 

874.  dirt  produced  by  different  pavements 624 

25,  842.  dirt  removed  from  streets. 10 

70.  granite  used  for  street  purposes  in  1889  (Table  VII) 30 

limestone  used  for  street  purposes  in  1880  (Table  XIII). .     37 
412.                       material  required  to  replace  wear  on  broken-stone  pave- 
ments   289 

414.                       material   used   to   replace  wear  on   broken-stone  pave- 
ments in  England 289 

$1   at   compound   interest   for  a  term  of  years  (Table 

LXXXIX) 800 

414.                      material   used  to  replace  wear  on   broken-stone  pave- 
ments in  France .  .  289 


INDEX.  827 


256.  Amount  of  paving-cement   manufactured   from   one   ton  of  refined 

asphaltum 184 

699.  rainfall 462 

refuse  collected  from  city  streets  (Table  LXXXVI) 623 

404.  rolling , 277 

sandstone  used  for  street  purposes  in  1889  (Table  X) 35 

366.  stone  broken  by  band 266 

618  transverse  rise  required  for  different  pavements  (Table    ' 

LXLV) 418 

859.  water  required  for  sprinkling  broken-stone  roads. ......  590 

913.  water  required  for  street  sprinkling 643 

101 ,  265#.     Analysis  of  Bermudez  aspbaltum 59, 1 96 

102.  Analysis  of  California  aspbaltum 60 

99/.  bituminous  limestones  (Table  XV) 52 

102.  sandstones 61 

116.  clay  (Table  XX)  82 

?  45.  macadam  pavement 250 

sandstone  (Table  VIII) 33 

1007*.  the  residue  of  refined  Trinidad  aspbaltum 57 

131.  Tompkins  Cove  gravel 95 

100<2.  Trinidad  asplialtum,  crude 55 

Alcatraz  liquid  asplialt 47 

Utah  liquid  asplialt 47 

Pittsburg  aspbaltic  flux 47 

Trinidad  aspbaltum,  refined 58 

103a.  and  tests  of  aspbaltum 62 

596.  Angle  of  repose 406 

645.  of  eartbs 425 

Angles  of  slopes  (Table  LXVI)  425 

Annual  cost  per  bead  of  population  for  street  maintenance  in  tbe 

United  States  (Table  LXXXVII) 627 

43.  Annual  cost  of  pavements. 16 

1045.  structures 797 

wood  pavements  in  London  (Table  XXXI) 136 

103^5.  Apparatus  for  penetration  tests  of  bitumen 66 

89#.  Appearance  of  aspbaltum 39 

405.  broken-stone  pavements  after  being  rolled. 278 

267.  European  bituminous  limestone 197 

lOOd  Trinidad  aspbaltum 55 

712.  Arcb-culverts 474 

960.  specifications  for , 665 

713.  tbickness  of  (Table  LXXV) 474,  476 

878,  895.  Area  cleaned  by  machine  brooms 628,  635 

878.  Area  cleaned  by  one  man 629 

793.  covered  by  a  barrel  of  Portland  cement 545 


828  INDEX. 


ARTICLE  PAGE, 

375.  Area  covered  by  a  cubic  yard  of  broken  stone 268 

793.  cubic  yard  of  concrete 268,  545 

256.  cubic  yard  of  prepared  asphalt 184 

171.  ton  of  granite  blocks  (Table  XXVI) 117 

302,  778.  ton   of  prepared  rock-asphalt  (Table  LXXX1V) 

212,  530 

of  tile-drains  (Table  LXXVII) 479 

690.  of  water-way  of  culverts ^62 

404.  rolled  by  steam-roller  per  day 277 

895.  swept  by  machine-brooms 635 

894.  one  man 635 

674.  Areas,  sectional,  of  earthwork,  formula  for  calculating, 447 

745.  Arrangement  of  city  streets 500 

751.  street-intersections 507 

streets  with  opposite  sides  at  different  levels 513 

979.  Artificial  foundation,  specifications  for 671 

443.  granite  blocks 308 

475.  Portland  cement 329 

822.  stone  curb  and  gutter,  specifications  for 568 

815.  curb  473 

786.  footpaths 542 

796.  specifications  for 314,  548 

825.  hollow  curb 570 

450/".  stone  pavements 314 

794.  wear  of 546 

279.  Asphalt  and  coal-tar    202 

281.  pavements,  advantages  of 203 

285.  cost  of  maintaining 204 

282.  defects  of 203 

291.  specifications  for. 205 

296.  block  pavement,  specifications  for 210 

292.  pavements 208 

294.  cost  of  construction  (Table  XXXVI) 210 

292.  blocks,  size  of. 208 

96.  cement 45 

155.  cement,  cushion-coat  for  stone  blocks 108 

252.  failure  of 178 

243.  cement  pavements 175 

92a,  93&.  Asphalte 42,  43 

103,  267.  comprime 62,  197 

103.  coule ,.' 62 

780,  781.  footpaths,  specifications  for 530,  532 

778.  for  footpaths 529 

100«,  103.  Asphalt  mastic 59,  62 

778,  781.  mastic  footway  pavements  in  Paris 529,  532, 


INDEX. 


829 


ARTICLE  PAGE 

435.  Asphalt  old,  mixed  with  broken  stone 802 

262.  one-coat  pavement 188 

874.  pavement,  amount  of  dirt  produced  by 624 

19.  and  rain "2 

894.  area  cleaned  by  one  man 635 

load  drawn  on,  by  a  horse  (Table  LVII). . . .  380 

221.  pavements,  advantages  of 159 

225.  and  street-car  rails 163 

222,  261.  and  variations  in  temperature 159,  185 

224.  brick  gutters  for 161 

303fZ.  condition  at  end  of  guarantee  period 217 

232.  cost  of  construction  (Table  XXXV)...  .168,  169 
887-889.  cleaning 627,  632,  633 

233,  234.  maintenance  (Table  XXXVtf).  .168, 173 
3036.                                            cracks  in 213 

222.  defects  of 159 

218.  difference  between  European  and  American  157 

3036.  disintegration  of 213 

97«,  227.  durability  of 47,  166 

8036.  expansion  joints  in 214 

303a.  expansion  of 213 

232.  extent  of,  in  1890 168 

252.  failure  of 178 

14.  foothold  on 7 

240.  foundation  for 174 

50.  guarantee-period 21 

303d.  condition  at  end  of 217 

266.  in  Europe 197 

226.  injured  by  illuminating  gas 164 

224.  injured  by  water 160 

223.  injurious  effects  of  sand  on 160 

217.  introduction  of 157 

27.  lifeof 11 

233.  maintenance,  cost  of 168 

265.  by  contract 194 

222,  261.  maximum  grade  for 160,  186 

261.  on  grades 186 

264^.  on  surface  of  old  pavements 192 

0036.  repair  of 213 

3036.  rolls  or  waves  in 213 

8036.  skimming  process  of  repair 215 

1 9-21.  slipperiness  of 9,  10 

:;!03eZ.  specifications  for  condition  at  end  of  guar- 
antee period 217 

:>63.  specifications  for,  on  bituminous  base 191 


830  INDEX. 


ARTICLE  FAGtt 

264.          Asphalt  pavements,  specifications    for,    on    hydraulic    concrete 

base 192 

303c.  specifications  for  repair  of 215 

263.  specifications  for,  Trinidad 186 

897.  squilgees  for 63G 

1039.  tools  used  in  the  construction  of 702 

228,  traffic  sustained  by ,. 107 

transverse  rise  for  (Table  LXIV) 418 

253.                                              Trinidad  composition  of  the  wearing  sur- 
face   183- 

303&.  waves  in 214 

231.  wear  of 168 

103a.  paving-cement,  amount  of  bitumen  in 63. 

256.  area  covered  by  a  cubic  yard  of 184 

257.  temperatures  for  working 184 

256.  weight  of  a  cubic  yard 184 

253,  255.  paving,  proportion  of  the  materials  used 183, 184 

263.  two-coat  pavement 187 

210.  wood  pavement 141 

90,  900,  95e.  Asphaltene 40,  45, 

470.  Asphaltic  cement  for  concrete 321 

96,  97,  1000,  102.  Asphaltic  cement 45,  47,  58;  61 

99&.  paving  compounds  ...     50 

99.  materials 50 

450?.  Asphaltina 318 

88.  Asphaltum 39 

103«.  analyses  and  tests  of 6'2 

92#,  102.  Asphaltum,  American 42,  60 

101,  265a.  Bermudez 59,  196 

265«.  analysis  of 196 

265«.  composition  of  the  wearing-surface  with  197 

89c.  characteristics  of 3<> 

90.  composition  of 40,  43. 

94.  crude •. 44 

104.  Cuban,  price  of  (Table  XVII) 74 

composition  of 43 

220,  different  varieties,  cost  of  preparing  the 158 

92.  distribution  of 41 

96a.  flux  for -itf 

104.  imports  of,  into  the  United  States  in  1890  (Table 

XIX) 74,75 

93.  nomenclature ; 42 

92.  occurrence  of 41 

104.  prices  of,  in  New  York  in  1897-98  (Table  XVII). .     74 

production  in  the  United  States  (Table  XVIII;. ...     74 


INDEX.  831 


95.  Asphaltum,  refining 44 

89c.  specific  gravity  of  (Table  XXIV) 40,  97 

100.  '    Trinidad 54 

analyses  of , 55 

1000.  characteristics  of  refined 55,  58 

100c7.  of  crude 5.1 

WOe,  243.  preparation  of 56,  175 

104.  price  of  (Table  XVII) 74 

100ft.  refined,  specific  gravity  of 58 

100ft.  composition  of 58 

257.  number  of  cubic  yards  to  one  ton  184 

100.  source  of 54 

1030.  tensile  strength  of 03 

105.  uses  of 75 

89.  varieties  of 39 

weight  of  (Table  XXIV) 97 

450/.  Artificial  stone 313 

1012.    Assignment  of  contract 679 

153.    Assorting  granite  blocks  at  the  quarry,  advantage  of 107 

410.    Atmospheric  changes,  effect  of,  on  pavements ' 284 

418.    Austria,  amount  of  material  used  in,  to  replace  wear  on  broken- 
stone  pavements , , £91 

1036.    Aveling  &  Porter  steam-roller 736-760 

Average  width  of  sidewalks  in  various  cities  (Table  LXXXII) 508 


B. 

629.  Balancing  transverse  of  earthwork 421 

881.  Baltimore,  street-cleaning  in 630- 

86.  Basalt,  description  of 38 

resistance  to  crushing  of  (Table  XXIV)   97 

specific  gravity  of  (Table  XXIV). 97 

weight  of  (Table  XXIV) < 97 

897.  Bass  brooms 636 

136.  Belgian  block  pavement 101 

172.                                             cost  of  construction  (Table  XXVIII) 119 

137.  defects  of 101 

138.  specifications  for 101 

418.  Belgium,  cost  of  maintaining  broken-stone  pavements  in 290 

572,  940.  Bench-marks 392,  658 

32.  Benefit,  economic,  of  good  pavements 13 

1 62.  Berea  sandstone Ill 

265a.  Bermudez  asphalt 1 96 

745.    Best  arrangement  of  city  streets 500 

449.  road .  311 


832  INDEX. 


ARTICLE  .  PAGE 

459.  Beton 321 

1029.  Bid,  form  of 693 

1U2S.  Bidders,  instruction  to 689 

380.  Binding  27 1 

891.  effect  of 273 

388.  using  large  quantities 272 

390.  necessity  of 272 

430.  power  of  clay 300 

389.  proportions  adopted  by  the  French  engineers 272 

388.  quantity  of 272 

897.  Birch  brooms 637 

101,  2650.  Bermudez  asphaltum 59,  196 

88,  94.  Bitumen 39,  43 

103a.  action  of  water  and  ammonia  on 63 

103«.  change  of,  due  to  age 63 

89^.  earthy 39 

896.  elastic 39 

103rt.  essential  characteristics  of 63 

89c.  hard 39 

103a.  amount  in  asphaltic  paving-cement 73 

93d  liquid 43,  47 

893.  specific  gravity  of  (Table  XXIV) 40,  97 

weight  of  (Table  XXIV) 97 

91.  originof 41 

1030.  penetration  tests  of 66 

103a.  softness  of 63 

89c.  specific  gravity  of 40 

103«.  stability  at  high  temperatures 63 

1030.  susceptibility  to  change  of  temperature 63 

103«.  viscosity  of 63 

96,  160.  Bituminous  cement,  composition  of 45,  109 

161;  cost  of 110 

160.  for  filling  joints 109 

161.  manner  of  using 110 

242,  263.  Bituminous  concrete 175,  191 

259.  limestone  pavements,   experience  with,  in  Wash- 
ington    185 

•277.  limestone  pavements  in  the  United  States 201 

specific  gravity  of  (Table  XXIV) 97 

268.  test  for 197 

94,996.  limestones  44,51 

268.  appearance  of  European 198 

99/.  how  used 51 

270.  preparation  of 199 

434.  macadam..  „ 301 


INDEX.  833 


^ARTICLE  PAGE 

297.  Bituminous  rock,  American 211 

303.  pavements,  specifications  for 212 

104.  production   of,  in  the  United  States  (Table 

XV1I1) 74 

99/.  rocks,  analyses  of  European  (Table  XV) 52 

102.  sandstones,  analyses  of 61 

99^.  in  America 52 

99^.  in  Europe 52 

99^.  preparation  of 52 

456.  Blast-furnace  slag  for  foundations  of  pavements 320 

•D30.  used  for  bricks 233 

450#.  paving 311 

663.  Blasting 441 

292.  Block  pavement  of  asphalt 208 

182.  Blocks  sapless  cedar 129 

81.  Bluestone,  amount  used  for  street  purposes  in  1889  (Table  XI)  .....     35 

831.  bridge-stones,  specifications  for 575 

S\S.  curb 566 

318.  specifications  for 566 

78.  description  of 33 

776,  1018.  flagging,  specifications  for 529,  685 

774.  for  footpaths 528 

resistance  to  crushing  (Table  IX) 34 

specific  gravity  of  (Table  IX) 34 

77.  uses  of 33 

value  of,  used  for  street  purposes  in  1889  (Table  XI) ....     35 

value  per  cubic  foot  (Table  XI) 35 

weight  of  (Table  IX)     34 

658.  Bogs,  embankments  across 435 

1007;  Bond  for  faithful  performance  of  work 678 

1 031 .  form  of 703 

1021.  indemnity 686 

866.  Books  kept  by  cantonniers 610 

632.  Borrow-pits 422 

4336.  form  of 422 

037.  staking  out 423 

133.  Boston,  cobblestone  pavements  in 99 

$82.  street  cleaning  in 630 

711.  Box-culverts 472 

711.  dimensions  of  (Table  LXXIV) 474 

597.  Brakes,  effect  of 406 

866.  Breaches  of  highway  law 609 

362.  Breaking  stone  by  hand 265 

365.  cost  of 266 

364.  machinery 266 

367.  cost  of, 266 


834 


INDEX. 


AKTICLK  PAGE 

60.  Breaking  tests  of  materials 24 

054.  Breast- walls,  specifications  for 663 

Brennan's  stone-crusher 737 

107.  Brick 77 

64.             absorptive  power  of  (Table  V) 27 

330.            blast-furnace  slag 233 

common  hard,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

450w.          copper  slag 316 

688.            drains 457 

784.  footpaths : 540 

785.  specifications  for , 541 

828.  gutters,  specifications  for 572 

224.  for  asphalt  pavements 160 

329.  iron 233 

masonry,  specific  gravity  of  (Table  XXIV) 97 

968.  specifications  for 667 

weight  of  (Table  XXIV) 97 

324.  McReynold's  patent 232 

877.  pavement,  cost  of  cleaning 626 

transverse  rise  for  (Table  LXIV) 418 

322.  variety  of  systems 230 

334.  variations  in  specifications  for 240 

304.  pavements 219 

305.  advantages  of 219 

326.  Charleston  plan 326 

320.  cost  of 227 

306.  defects  of 219 

307.  durability  of 221 

318.  expansion  joints  in : 223 

308.  experience  with 221 

309.  failuresof 221 

334d.  for  country  roads. 243 

316.  foundation  for 223 

319.  joint-filling  for 225 

27.  life  of 11 

318.  manner  of  laying 223 

601 .  maximum  grade  for 407 

334c.  number  of  brick  per  square  yard 242 

317a.  sand  cushion 223 

331-334.  specifications  for 233-240 

327.  Wheeling  plan 232 

64,  119.     paving,  absorptive  power  of  (Table  V  and  Table  XXI) 27,  87 

117.  characteristics  of  good. , 82 


INDEX.  835 


ARTICLE  PAGE 

323.  Brick,  paving,  Hal  wood  block 231 

114.  manufacture  of 79 

834e.  price  of,  per  thousand 245 

314.  quality  of 222 

111.  quality  of  clay  for .. ...     78 

119.  resistance  to  crushing  of  (Tables  XXIa,  XXIV) 

86,  88-91,  97 

313.  shape  of 222 

313.  size  of 222 

119.                              specific  gravity  of  (Table  XXI  and  Table  XXIV)...  87,  97 
322.  the  Hayden 2oO 

117,  119.  weight  of  (Table  XXI  and  Table  XXIV) 87,  97 

pressed,  resi>tance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV)  97 

soft  inferior,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

standard  tests  for 86 

Stourbridge  fire,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV). 97 

weight  of  (Table  XXIV). 97 

118.  tests  of 82 

Ohio  paving  (Table  XXI«) 88-91 

Brickwork  in  cement-mortar,  resistance  to  crushing  (Table  XXIV)  ...     97 

575.  Bridge  sites,  selection  of 395 

720.  specifications  for. , 486 

720.  substructure  of 483 

830.  stones 573 

831.  specifications  for 575 

421.  Bridgeport,  Conn. ,  broken-stone  pavements  in 292 

71 5.  Bridges c 780 

858.  examination  of 589 

716.  live  loads 780 

718.  materials  for . .  481 

716.  proportioning  of 780 

933.  setting  out 655 

435.  Broken  stone,  and  old  asphalt 302 

375.  area  covered  by  a  cubic  yard 268 

373.  determination  of  the  voids  in  0 268 

410.  pavement,  action  of  the  weather  on 284 

874.  amount  of  dirt  produced  by 624 

859.  water  required  for  sprinkling 592 

894.  area  cleaned  by  one  man 635 

360.  breaking  the  stone 265 


836  INDEX. 


ARTICLE  PAGE 

877.  Broken-stone  pavement,  cost  of  cleaning 020 

406.  rolling 280 

344.  defects  of  Telf ord's  system 249 

408.  difference    in    the    cost    of   European   and 

American 283 

410.  effect  of  horse's  hoofs  on 284 

410.  wheels  on 284 

412.  mud  on .:...  289 

load  drawn  by  a  horse  on  (Table  LVII) 880 

405.  manner  of  applying  the  roller 278 

381 .  sand  core  for 270 

transverse  rise  for  (Table  LXIV) 418 

338.  Tresaguet's  method 246 

335.  pavements 246 

346.  advantages  of , 250 

396.  rolling 274 

414.  amount    of    material    required     to    replace 

wear 289 

404.  amount  of  rolling  required  , 277 

405.  appearance  of,  after  being  rolled 278 

413.  average  annual  loss  of  thickness 289 

393.  compacting  the  stone 273 

393.  by  the  traffic 273 

397.  horse-rollers 273 

398.  steam-rollers 275 

381.  core  for.    270 

407.  cost  of  (Tables  XLI  and  XLII) 281,  282 

418,  860.  maintenance 290,  592 

347.  defects  of 350 

350.  erroneous  methods  of  construction 251 

349.  essentials  necessary  to  successful  construc- 
tion    251 

880.  failure  of 270 

15.  foothold  on 7 

421.  in  Bridgeport   Conn 292 

420.  Chicago ' 292 

413.  loss  of  thickness 289 

340.  MacAdam's  method 248 

850.  maintenance  of 583 

415.  manner  of  restoring  thickness 289 

C01.  maximum  grade  for 407 

419.  modern,  in  England 291 

o~>l.  quality  of  stone  for 252 

417.  recoating,  when  it  should  be  done 290 

861.  repairof 596 


INDEX.  837 


ARTICLE  PAGE 

359.  Broken-stone  pavements,  shape  of  stones  for 265 

357.  size  of  stone  for 265 

423.  specifications  for 297 

383.  spreading  the  stone 270 

339.  Telford's  method 247 

378.  thickness  of 269 

384.  layers 271 

1036.  tools  employed  in  the  construction 734 

1037.  maintenance .761 

traction  on  (Table  L) 372 

392.  watering,  use  of 278 

63,409.  wearof 25,  284 

382.  quantity  required  per  mile  for  different  widths  (Table 

LX) 384 

1019.  specifications  for 685 

387.  screening  of 272 

372,461.  voidsin 267,  322 

374.  weightof 268 

883.  Brooklyn,  N.  Y.,  street  cleaning  in '. 632 

897.  Brooms,  bass 636 

897.  birch 636 

1840.  prices  of 770 

897.  rattan 636 

897.  steel- wire 636 

102«.  Buena  Vista  asphalt 61 

1017.  Bulkhead,  specifications  for  a 681 

C 

674.  Calculating  amount  of  earth- work  447 

676.  the  half-widths  and  areas  of  earth- work 448 

102.  California  asphaltum 60 

104.  bituminous  rock,  price  of 74 

102.  analysis  of 60 

866.  Cantonniers,  absence,  fines  for 611 

annual  gratuities 611 

appointment  of 605 

books 610 

chief 605 

classification  of 610 

compulsory  attendance  of 609 

distinctive  mark 610 

duties  of 604 

fines  on  account  of  absence 611 

gratuitous  assistance  to  travellers  by 609 


838  INDEX. 


ARTICLE  PAGE 

866.  Cantonniers,  indemnity  for  removal  of 611 

leave  of  absence 610 

means  of  verifying  absence  of 610 

regulations  for  604 

salary  of 610 

surrender  of  books  and  distinctive  marks  on  dismissal 

of  a 610 

surveillance  over  breaches  of  the  highway  law 609 

tools  furnished  by  the  609 

to  the 609 

keeping  in  repair  by 610 

working  hours  of 608 

Capacity  of  drill-holes  (Table  LXVIII) 442 

1033.  scrapers 713 

sprinkling-carts 634 

1036.  stone-crushers... 736 

39.  Care  of  pavements 14 

1033.  Carts,  capacity  of 717 

•    earth 717 

898.  for  street  dirt 636 

sprinkling,  capacity  of .    634 

price  of 634 

1042.  Cast-iron  gutter-crossings 788 

specific  gravity  of  (Table  XXIV) 97 

984.  specifications  for 672 

1042.  Catch-basin  covers 786 

761 .  Catch-basins 516 

1018.  specifications  for 685 

704.  -pools,  use  of 466 

696.  -water  ditches 461 

951.  specifications  for 663 

858,  869.  Causes  producing  dirt 587,  620 

208,  216&.  Cedar-block  pavement 140,  154 

208.  pavements 140 

216.  specifications  for 150 

482.  Cement,  activity  of 334 

485.  age,  effect  of 33(5 

473.  American  natural,  specification <*:  28 

requirement  for 328 

amount  of  water  absorbed  by  (Table  XLIV) 336 

475.  artificial  Portland 329 

96,  100, 102.  asphalt 45,  52,  60 

160.  bituminous,  composition  of 109 

161.  cost  of 110 

161.  manner  of  using 110 


INDEX.  839 


ARTICLE  PAGE 

473,  479.  Cement,  color  of  American  natural 328,  333 

510.  data  for  estimates 358 

483.  effect  of  variations  of  temperature  on 334 

475.  English  Portland,  specific  gravity  of  (Table  XXIV). . . .  97,  329 

476.  weight  of  (Table  XXIV) 97,  331 

790.  expansion  of 543 

Frencli  Portland,  weight  of  (Table  XXIV) 97 

473.  hydraulic 328 

490.  measuring  fineness  of t 339 

494.  -mortar,  composition  of 342 

474.  natural  Portland 329 

706.  pipe  f°r  culverts 467 

707.  cost  of 471 

dimensions  of 471 

161.  Portland  and  iron  slag  for  filling  joints 110 

476.  characteristics  of 331 

475.  effect  of  sand  on 331 

509.  English  specifications  for 357 

476.  489.  fineness  of 331,  338 

477.  necessity  of  testing 332 

476.  specific  gravity  of 332 

476.  tensile  strength  of 332 

973.  test  for 669 

476.  weight  of ; 331 

482.  quick-  and  slow-setting,  definition  of 334 

Roman,  specific  gravity  of  (Table  XXIV). 97 

weight  of  (Table  XXIV) 97 

973.                   Rosendale,  test  for 669 

473.                   specific  gravity  of  American  natural 328 

972.  specifications  for 669 

473.                   strength  of  American  natural 328 

492.                  testing  machine 340 

477.  necessity  of , 332 

477.                  tests 332 

973.  specifications  for 669 

•  473.  weight  of  American  natural  (Table  XXIV) 97,  328 

356a.  Cementation  test,  description  of 260 

45.  Census,  traffic 17 

48.                           form  of 19 

962.  Centring,  specifications  for 666 

450£.  Ceramocrystal   pavement 31 5 

10310.  Certificate  of  acceptance 709 

1031/.  Certificate  of  final  acceptance 709 

1031c.  Certificates,  form  of  monthly 707 

Chalk,  resistance  to  crushing  of  (Table  XXIV) 97 


840  INDEX. 


ARTICLE  PAGK 

Chalk,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

89a.  Chapapota 39 

457.  Character  of  concrete  for  pavement  foundations 321 

453.                         natural  soils 319 

543.                         vehicles 383 

473.  Characteristics  of  American  natural  cements 328 

89.                                  asphaltum 39 

268.                                  European  bituminous  limestone 198 

117.                                  good  paving-brick 82 

499.                                   mortar 344 

476.                                    Portland  cement . .        331 

100&                                 crude  Trinidad  asphaltum 55 

100/2..                                refined  Trinidad  asphaltum 58 

448.  Charcoal  roads 310 

326.  Charleston  plan  of  brick  pavements 232 

29.  Cheapest  pavement 11 

lOOa.  Cheese  pitch 54 

122,  188.  Chemical  treatment  of  wood 93,  131 

132a,  450c.  Chert , 96,  312 

420.  Chicago,  broken-stone  pavements  in 292 

Chief  cantonnier 605 

862.             foreman,  duties  of 597 

819.  Circular  curb 567 

pipes,  discharging  capacity  of  (Table  LXXXVIII) 479 

31.  City  ownership  of  street-car  tracks 13 

744.           streets 500 

873.                      amount  of  refuse  collected  from  (Table  LXXXVI) 623 

746.  best  arrangement  of 500 

749.                     gradeof 506 

748.                      maximum  grade  of,  in  various  cities 506 

747.  width  of  (Table  LXXXII) 506,  508 

1105.  Claims,  payment  of 677 

949.  Classification  of  earth-work 662 

107.  Clay 77 

116.          analyses  of  (Table  XX) 82 

430.          binding  power  of 300 

113.          color  of 79 

108.  composition  of 77 

450d.  Florida 312 

111.  for  paving-bricks 78 

426.  proportion  of,  to  gravel 299 

835.  roads,  improving  of 577 

836.  maintenance  of 578 

836.  trees  on..  .  578 


INDEX.  S4L 


ARTICLE  PAGE 

639.  Clay,  shrinkage  of 428 

686.  soils,  drainage  of.   455 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

with  gravel,  specific  gravity  of 97 

weight  of 97 

127.  sand 94 

1011.  Cleaning  up,  specifications  for 679 

40.  of  pavements 15 

126.  Cleanness  of  sand,  to  test 94 

868.  Cleansing  of  streets 619 

877.  cost  of 626 

875.  methods  employed 624 

944.  specifications  for 660 

1040.  tools  employed  for 770 

944.  Clearing,  specifications  for 660 

1032.  Clearing,  tools  for 710 

884.  Cleveland,  Ohio,  street  cleaning  in 632 

418.  Climate,  effect  of,  on  roads 290 

450/i.  Clinkers 314 

945.  Close  cutting,  specifications  for 660 

279.  Coal-tar  and  asphalt 202 

281.  pavements,  advantages  of • .  208 

284.  cost  of  maintaining 204 

282.  defects  of 203 

291.  specification  for 205 

278.  pavements 201 

450p.  paving-blocks 317 

1 06.  paving-pitch 75 

827.  Cobblestone  gutters,  specifications  for  laying 571 

133.  pavement 99 

172.  cost  of  (Table  XXX) 120 

133.  in  Boston 99 

133.  Philadelphia 99 

166.  on  steep  grades Ill 

135.  specifications  for 99 

Coefficients  for  retaining-walls  (Table  XXXI) 492 

352.  of  quality  of  stones  for  broken-stone  pavements  (Table 

XXXVIII)  260 

982.  Cofferdams,  specifications  for 671 

687.  Collars  for  tiles 456 

89a,  lOOd.  Color  of  asphaltum , 39,  55 

473,  479.  cements 328,  33:) 

113.  clay 79 

65.  granite 27- 


842  INDEX. 


ARTICLE 

74.                Color  of  sandstone 32 

86.                                 trap 38 

450.  Combinations  of  wood  and  iron 311 

Common  hard  brick,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of 97 

weight  of 97 

472.                   lime 327 

1001.  Commencement  of  work 676 

79.  Commercial  names  of  sandstones 34 

393.  Compacting  the  broken  stone 273 

104.  Comparative  prices  of  asphaltum  in  1897-98  (Table  XVII) 74 

rank  of  pavements  (Table  IV)  21 

15.  safety  of  pavements 7 

1002.  Completion,  time  of 676 

90.  Composition  of  asphaltum  (Table  XlVa) 40,  43 

160.  bituminous  cement 109 

494.  cement-mortar 342 

108.  clay 77 

459.  concrete 321 

872.  mud  (Table  LXXXV) 622 

872.  street  dust ...  621 

782a.  Compressed-asphalt-tile  footway-pavement 539 

468.  Compressive  strength  of  concrete '  325 

502.  mortar 347 

866.  Compulsory  attendance  of  the  cantonniers 609 

623.  Concave  cross-section 420 

466.  Concrete,  amount  of  ramming  required 324 

470.  and  furnace-slag 327 

792.  area  covered  by  a  cubic  yard 545 

242.  bituminous 175 

460.  character  of,  for  pavement  foundations 322 

459.  composition  of 321 

468.  compressive  strength  of 325 

469.  costof 326 

459.  definition  of - 321 

459.  essentials  necessary  to  the  manufacture  of  good 321 

791.  footpaths 543 

795.  specifications  for 547 

460.  for  pavement  foundations 322 

470.  formed  with  asphaltic  cement 327 

154.  foundations,  thickness  of 108 

466.  layingof 324 

436.  macadam 302 

465.  mixing  of 324 

machine,  price  of 768 


INDEX.  843 


471 .  Concrete,  mortar  for 327 

461,  462.  proportions  of  ingredients 322 

459.  quality  of  stone  for 321 

464.  quantity  of  materials  required  for  one  cubic  yard 323 

463.  water  required  for 323 

466.  ramming  of , 324 

127.  sandfor 94 

459.  size  of  stone  for. . .  ., 322 

460.  specific  gravity  of  (Table  XXIV) 97,  322 

.512-516,  977.     specifications  for 359-362,  670 

460,  468.  strength  of 322,  325 

458.  thickness  of 321 

467.  transverse  strength  of 325 

461.  usual  proportions  of  ingredients 322 

457.  weight  of  (Table  XXIV) 97,  321 

791.  rammers  for 545 

28.  Considerations  concerning  cost  of  pavements 11 

942.  tests  of  materials 659 

555.  governing  location  of  roads 389 

42.  Consequential  damages 15 

444.  Construction  of  plank  roads 308 

739.  roads  along  the  seashore  or  margins  of  rivers 494 

184.                                wood   pavements,   essentials   necessary  to  the  suc- 
cessful  130 

593.  profile 404 

560.  Contour  lines 390 

625.  transverse  on  hillside  roads 420 

618.  of  roadway 418 

756.  streets 512 

1003.  Contract,  forfeiture  of 676 

1030.  form  of 694 

1014.  prices  in 679 

1012.  subletting  of 679 

943.  Contracts 660 

476.  Contraction  of  Portland  cement 331 

988.  Contractor  defined 672 

989.  notice  to 672 

1012.  personal  attention  of 679 

1031(2.  Contractor's  affidavit 708 

621.  Convexity,  excessive,  objections  to 418 

450w.  Copper-slag  brick 316 

447.  Corduroy  roads 310 

381.  Core  for  broken-stone  pavements 270 

450£.  Cork  pavement 316 

43.  Cost,  annual,  of  pavements 16 


844  INDEX. 


ARTICLE  PAGE 

1045.  Cost,  annual,  of  structures 797 

wood  pavements  in  London  (Table  XXXI) 13fr 

per  head  of  population  for  street  maintenance  in  the 

United  States  (Table  LXXXVII) 627 

33.  first,  of  pavements 13 

44.  gross,"  1(> 

161.  of  bituminous  cement 110 

363.  breaking  stone  by  hand 26fr 

320.  brick  pavements  (Table  XXXVIII) 230 

469.  concrete 32fr 

300.  construction  of  American  bituminous- rock  pavements 212 

294.  asphalt-block  pavements  (Table  XXXVI)...  210 

232.  asphalt  pavements  (Table  XXXV) 169 

172.  Belgian  block  pavements  (Table  XXVIII)  . .   119 

407.  broken-stone  pavements  (Table  XLII) ,  281 

172.  cobblestone  pavements  (Table  XXX) 120 

172.  granite-block  pavements  (Table  XXVII) 118 

432.  gravel  pavements  (Table  XLIII) 301 

172.                                             sandstone  pavements  (Table  XXIX) 1 19- 
20S,                                            wood  pavements  (Table  XXXIII) 13£ 

899.  crematories. ...   636- 

188.  creosoting  wood 133. 

710.  different  forms  of  culverts 472 

688.  drains 457 

drain-tiles  (Table  LXXVII) 47£ 

840.  earth  roads 579- 

672.  -work 445- 

706.  earthenware  culvert-pipe 4G7 

668.  excavating  rock 443 

742.  fencing 496> 

709.  iron  pipe-culverts  (Table  LXXIII) 47£ 

233.  maintaining  asphalt 168 

418,  860.  broken-stone  pavements  290,  592 

841.  earth  roads 580 

169.  granite-block  pavements 114 

403.  steam  rollers 27ft 

193,  206.  wood  pavements   (Tables   XXXI  and  XXXIV) 

136,  140 

905.  melting  snow 638 

886.  operating  machine  brooms.. .  632 

1033.  ploughs 711 

368.  stone-crushers , , 266 

28.  pavements,  considerations  concerning 11 

446.  plank  roads 310 

707.  Portland-cement  pipe  (Table  LXXII) 471 


INDEX.  845 


-ARTICLE  PAGE 

220.  Cost  of  preparing  the  different  varieties  of  asphalt 158 

371.  quarrying  stone  (Table  XXX) , 267 

900.  removing  snow c 637 

406.  roll  ing .280 

164.  sandstone  pavements Ill 

41 .  service  of  pavements 15 

369,  370,  1036.  Cost  of  stone-crushers 267,  736 

371.  crushing  (Table  XXXIX) 268 

877,  893.  Cost  of  street  cleaning „ 626,  635 

915.  sprinkling 644 

893.  sweeping 635 

439.  Cost  of  trackways 306 

707.  vitrified  pipe  culverts  (Table  LXXI) 471 

5.  wagon  transportation  (Table  I) 2,  794 

878.  per  capita  for  street  maintenance  (Table  LXXXVII) 627 

216e.  Cottonwood  blocks 155 

555.  Country  roads,  location  of 389 

862.  County  engineer 599 

650.  Covering  of  slopes , 428 

1042.  Covers  for  catch-basins  . , 786 

899.  Crematories,  cost  of 636 

122,  188.  Creosoting  wood 93,  132 

588.  Crookedness,  objections  to 403 

573.  Cross-levels 392 

677.  -section  of  earth-work 448 

770.  -slope  of  footpaths 527 

1033.  -ties,  number  per  mile 720 

830.  Crossing-stones 573 

830.  dressing  of 573 

830.  quality  of 573 

832.  relaying 575 

831.  specifications  for 575 

755.  Crowns  in  gutters 512 

94.  Crude  asphaltum 44 

10436.  petroleum  for  sprinkling  roads 795 

369,  370.  Crushers,  capacity  of.   266,  736 

369,  370.  stone,  cost  of * 266,  736 

367.  operating. 266 

370.  horse-power  required  for 267,  736 

369.  size  of 267,  736 

368.  wear  of , . .  266 

132&.  Crushing,  resistance  to,  of  basalt  (Table  XXIV) 97 

brick  (Table  XXIV) 97 

cast  iron  (Table  XXIV) 97 

4'  chalk  (Table  XXIV). 97 


846  INDEX. 


ARTICLE 

132a.  Crushing,  resistance  to,  of  common  hard  brick  (Table  XXIV) 97 

69.  granite  (Table  VI) 28 

1320.  lead  (Table  XXIV) 97 

85,  ligonier 37 

84.  limestone  (Table  XII) 37 

1320.                                                    materials  (Table  XXIV) 97 

]  19.                                                      paving-brick  (Table  XXIV) 97 

132«.                                                    pressed  brick  (Table  XXIV) 97 

81.                                                    sandstone  (Table  IX) 34 

132a.                                                  soft  brick  (Table  XXIV) 97 

Stourbridge  (Table  XXIV) 97 

86.  trap-rocks  (Table  XIV) 38 

132#.                                                    wrought-iron  (Table  XXIV) , .  97 

120.                                                    wood  (Table  XXII) 92 

371.                     stone,  cost  of  (Table  XXXIX)  268 

60.  tests 24 

104.  Cuban  asphaltum,  price  of  (Table  XlVa  and  Table  XVII). 43,  73 

Cubic  contents  of  embankments  and  excavations  (Table  LXX) 453 

377.  yard  of  broken  stone,  area  covered  by  a 270 

464.  concrete,  materials  required  for 323 

1 53.  Culling  of  stone  paving-blocks 107 

697.  Culverts 462; 

712.  arcli 474 

699.  area  of  water-way 462 

711.  box 412 

711.  dimensions  of. 472 

706.  cement  pipe  for 467 

707.  cost  of  cement  pipes  for 471 

707.  vitrified  pipe 471 

970.  dry  box,  specifications  for 6fi8 

706.  earthenware  pipes  for 467 

702.  formula  for  calculating  the  area  of  water-way 465 

708.  iron  pipes  for 471 

932.  length  of 654 

705.  materials  for 466 

971.  pipe,  specifications  for 668 

955,  960.  specifications  for 664,  665 

931.  staking  out 6~>3 

821 .  Curb,  setting,  specifications  for 567 

937.  stakes  for 657 

1018.  specifications  for 682 

8 1 3.  Curbing 562 

815.  artificial  stone 564 

822.  specifications  for 568 

817,819.          bluestone,  specifications  for 566 


INDEX.  847 


ARTICLE  PAGE 

818.  Curbing,  circular 566 

813.  dimensions  of 562 

815.  fire-clay 564 

816.  granite,  specifications  for 565 

825.  hollow,  of  artificial  stone 570 

815.  iron 564 

814.  materials  employed  for .• 563 

823.  old,  dressing  of , 570 

824.  resetting,  specifications  for 570 

813.  setting  of 562 

585.  Curves 401 

586.  grade  on 401 

929.  staking  out  of 652 

610.  vertical  use  of 415 

587.  width  of  roadway  on 403 

589,  590.  Curving  and  straight  roads,  difference  between 403 

155.  Cushion-coat  for  granite  blocks 108 

155.  quality  of  sand  for 108 


D 

1009.  Damage  and  loss 678 

42.  Damages,  consequential 15 

1004.  for  non-completion 677 

842.  Data  required  to  calculate  the  value  of  improvements 580 

558.  for  the  location  of  roads 389 

181.  Death-rate  and  wood  pavements 127 

849.  Decreasing  the  length,  profit  of 582 

42.  Defective  pavements,  cost  of 15 

998.  work 674 

222.  Defects  of  asphalt 159 

1 37.  Belgian-block  pavements 101 

306.  brick  pavements 219 

347.  broken-stone  pavements 250 

282.  coal-tar  and  asphalt  pavements 203 

393.  compacting  broken  stone  by  the  traffic 273 

846.  existing  roads 581 

143.  granite-block  pavement 102 

345.  Macadam's  pavements 250 

186.  plank  and  sand  foundation 130 

454.  sand  foundations 320 

344.  Telford's  pavements 249 

178.  wood  pavements 124 

627.  Definition  of  earth-work 421 

852.  maintenance 585 


848  INDEX. 


ARTICLE  PAGE 

83.  Deposits  of  asphaltum 89 

862.   Depots  for  broken  stone 599 

666.  Depth  of  hole  drilled  by  hand 443 

667.  machine  drills 443-732 

88.  D&scription  of  asphalt 39 

78.  bluestone 33 

459.  *  concrete 321 

65.  granite 28 

82.  limestone 35 

74.  sandstones 32 

941.  specifications 659 

Designation  of  grades  (Table  LXII) 414 

10.  Desirability  of  pavements 5 

55.  Destruction  of  pavements 22 

450&.  Destructor  concrete 316 

996.  Details,  right  to  alter 673 

595.  Determination  of  grades 406 

604.  the  maximum  grade 4U8 

372,  461.  voids  in  broken  stone 267,  322 

885.  Detroit,  street  cleaning  in  632 

995.  Deviations  from  specifications , 673 

Diameter  of  horse-rollers 753 

steam     "       753 

689.  tiles 457 

549.  wheels ». . .  387 

218.  Difference  in  cost  between  American  and  European  asphalt 157 

408.                                 of  broken-stone  pavements  in  Europe  and  Amer- 
ica   , 283 

189.  Dimensions  of  blocks  for  wood  paving 133 

711.  box-culverts  (Table  LXXIV) 474 

313.  bricks  for  paving 86-222 

813.  curbing 562 

466.  rammers  for  concrete 21 

146.  stone  blocks  for  paving 1 04 

1036.  crushers 737 

wooden  bridges  (Tables  LXXIX,  LXXX) 484 

707.  weight,  and  prices  of  vitrified  pipe 471 

874.  Dirt,  amount  produced  by  different  pavements 624 

23.  and  durability  of  pavements 10 

898.  carts 636 

869.  Dirt-producing  causes 620 

Discharging  capacity  of  pipes  (Table  LXXVIII) 479 

991.  Dismissal  of  incompetent  workmen 673 

1023.  Disposal  of  old  materials 686 

900.  snow .  637 


INDEX.  849 


ARTICLE  PAGE 

899.  Disposal  of  street  dirt 637 

924.  Distance  apart  to  plant  trees 650 

283.  Distillate  pavements  in  Washington,  D.  C 204 

Distinctive  marks  of  cantonniers 610 

92.  Distribution  of  asphaltum 41 

692.  Ditches,  cleaning  out 459 

692.  side 459 

685.  Division  of  natural  soils  with  reference  to  draining 455 

689.  Drain-tiles,  dimensions  of 457 

682.  Drainage,  kinds  of 455 

452.  necessity  of 319 

655.  of  embankments 433 

452.  foundations 319 

803.  grade- walks 554 

647.  side-slopes 426 

651.  slopes 430 

758.  sub-foundation  of  streets ' 513 

693.  the  surface  of  roads 459 

759.  streets 516 

762.  -surface  at  street-intersections 520 

683.  Draining,  methods  employed  for 455 

1034.  tools  for 727 

668.  Drains 456 

688.  cost  of 457 

691.  fall  of 457 

form  of 458 

687.  materials  for 456 

686.  mitre 455 

687.  outlets,  protection  of 456 

950.  specifications  for 663 

934.  staking  out 655 

689.  tile 457 

688.  tiles,  cost  of 457 

size  of  (Table  LXXVII) 479 

weight  of  (Table  LXXVII) 479 

532.  Draught  of  horses 377 

"830.  Dressing  of  crossing-stones 573 

149.  stone  paving-blocks . , 105 

773.  stones  for  footpaths 528 

Drill-holes,  capacity  of  (Table  LXVIII) 442 

663.  depth  of 442 

663.  diameter  of 442 

Drills,  steam,  price  of 732 

970.  Dry  box-culverts,  specifications  for 668 

969.  masonry,  specifications  for 667 


850  INDEX. 


ARTICLE  PAGE 

721.  Dry-stone  retaining- walls 486 

Dump-cars,  capacity  of 719 

670.  -wagons 444-721 

25.  Durability  and  dirt 10 

61.  methods  of  testing 25- 

779.  of  asphalt  footpaths 530 

27,  97a,  227.  pavements 11,47-166 

27,  307.  brick  pavements 11,  221 

27,  167.  granite  blocks 11,  143 

23.  pavements 10- 

27,  193.  wood  pavements 11,  135 

Duration  of  a  horse's  daily  labor  and  maximum  velocity  unloaded 

(Table  L1V) 378 

872.  Dust,  street,  composition  of ....  621 

899.  removal  of 636 

866.  Duties  of  the  cantonniers. . . . 604 

862.  '  chief  foreman t . . .  597 

862.  foremen 597 

518.  Dynamometer  experiments 366,  374,  385 


E 

641.  Earth,  adhesion  of 424 

645.  angle  of  repose  of 425 

647.  effect  of  moisture  on 426 

669.  loosening  of 444 

645.  "  natural  slopes  of 425 

840.  roads,  cost  of 579 

841.  maintaining 580 

load  drawn  by  a  horse  on  (Table  LVII) 380 

transverse  rise  for  (Table  LXIV) 418 

839.  use  of  scraping-machine  on 579 

640.  settlement  of 423 

specific  gravity  of  (Table  XXIV) 97 

642.  stability  of 424 

670.  transport  of , , 444 

weight  of  (Table  XXIV) 97 

674.  -work,  calculating  the  amount  of 447 

949.  classification  of 662 

672.  cost  of 445 

677.  cross-sections 448 

627.  definition  of 421 

634.  equalizing  of 422 

641.  failure  of 424 

679  formulas  for  calculation  of  sectional  areas 450- 


INDEX.  851 


ARTICLE  PAGE 

676.  Earth -work,  half- widths  and  areas 448 

949.                          measurement  of 662 

651.  slipsof 428 

table  of  cubic  contents 453 

629.                         transverse  balancing 421 

706.  Earthenware  pipe  for  culverts 467 

89a.  Earthy  bitumen 39 

32.  Economic  benefit  of  good  pavements 13 

34.  Economies  of  pavements,  the  relative 14 

31.  Economy  and  public  bodies 12 

557.                    of  motive  power 389 

1 3.                          smoothness 6 

1048.                     relative,  of  materials. 806 

410.  Effect  of  atmospheric  changes  on  pavements 284 

388.                    binding -272 

392.                    excessive  watering 273 

507.                     frost  upon  mortars 351 

531.                    grades  upon  the  load  drawn  by  horses  (Table  LVIII) 381 

410,  1044.          horses'  feet  on  pavements 284,  797 

647.                    moisture  on  earth 426 

544.                    narrow  tires „ 384 

7.                    reducing  the  cost  of  wagon  transportation 4 

475.                     sand  on  strength  of  Portland  cement 330 

504.                     size  of  grain  of  sand  on  strength  of  mortar  (Table  XLVIII)  350 

[  386.                    using  large  quantities  of  binding 271 

554.                    vehicle  springs 388 

410.                     wheels  on  pavements 284 

615.                     width  on  cost  of  maintenance 416 

89&.  Elastic  bitumen 39 

847.  Eliminating  unnecessary  grades,  profit  of 581 

652.  Embankments  430 

658.  across  bogs 435 

657.                                          marshes 433 

655.  drainage  of 433 

653.  formation  of 430 

659.  on  hillsides 436 

656.  over  plains 433 

654.  side-slopes  of 432 

948.                           specifications  for 661 

987.  Engineer  defined 672 

990.  Engineer's  marks,  preservation  of 673 

414.  England,  amount  of  material  used  in,  to  replace  wear  on  broken- 
stone  pavements 289 

lOOc.  Epuree ; 54 

G28.  Equalizing  earth- work 421 


852  INDEX. 


ARTICLE  PAGE 

350.  Erroneous  methods  of  constructing  broken-stone  pavements 251 

452.  Essentials  necessary  to  the  formation  of  good  foundations 319 

349.  successful   construction  of   broken-stone 

pavements 252 

459.                                                 manufacture  of  good  concrete 321 

609.  Establishing  the  grade 415 

1043.  Europe,  prices  of  labor  in 793 

266.  European  aspbalt  pavements 197 

259.                                                     experience  with,  in  America 185 

268.                      bituminous  limestone,  appearance  of 198 

268.                                                            characteristics  of 198 

rocks,  analyses  of 52 

1005.  Evidence  of  the  payment  of  claims „ 677 

858.  Examination  of  bridges 589 

577.  Examples  in  location 396 

662.  Excavating  rock 440 

978.  Excavation,  foundation,  specifications  for 671 

31,  57.  Excavations  in  streets 13,  23 

621.  Excessive  convexity,  objections  to 418 

392.                      watering,  effect  of 273 

303&.  Expansion  of  asphalt 213 

318.                             brick  pavements 223 

476,  790.                      cement 332,  543 

190.                             wood-paving  blocks 134 

308.  Experience  with  brick  pavements 221 

259.                                            European  asphalt  pavements  in  America 185 

84,  165.                                  limestone  paving 36,  111 

662.  Explosives,  quantity  required  (Table  LXVII) 441 

232.  Extent  of  asphalt  pavements  in  1890  (Table  XXXV) 168,  169 

Belgian  block  pavements  (Table  XXVIII) 119 

brick  pavements  (Table  XXXVII) 228 

cobblestone  pavements  in  1890  (Table  XXX) 120 

granite                  "          (Table  XXVII) 118 

gravel                   "          (Table  XLIII) 301 

macadam              "          (Table  XLII) 282 

sandstone  pavements  in  1890  (Table  XXIX) 119 

wood  pavements  in  1890  (Table  XXXIII) 139 


F 

252.  Failures  of  asphalt  pavements 178 

309.  brick  pavements 221 

641.  earth-work 424 

727.  retaining-walls .    ....   491 

380.  thin  broken-stone  pavements . , 270 


INDEX.  853 


ARTICLE  ,  PAGE 

186.  Failures  of  wood  pavements 1 30 

1007.  Faithful  performance  of  work,  bond  for . 678 

691.  Fall  of  drains 457 

22.  Falls  of  horses,  kinds  and  causes  of 10 

1036.  Farrell  stone-crusher 738 

Feldspar,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

65.  Feldspathic  rock >28 

741.  Fencing 496 

743.  cost  of 499 

741.  specifications  for 496 

354.  Fieldstone 258 

280.  Filbert  vulcanite  pavement 202 

160,  192.  Filling  for  joints  in  pavements 109,  134 

592.  Final  location 404 

576.  selection  of  route 396 

920.  Financial  value  of  trees C49 

476,  489.  Fineness  of  Portland  cement 331,  338 

504.  sand  for  mortar 347 

815.  Fire-clay  curb.. 564 

956.  First-class  masonry 664 

33.  cost  of  pavements 13 

1018.  Flagging,  specifications  for 682. 

776.  Flagstone,  specifications  for 529- 

Flint,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

450<Z.  Florida  clay 312 

96a.  Flux  forasphaltum , 46 

14,  524.  Foothold,  influence  of 7,  374 

786,  artificial  stone  for 542 

778.  Footpaths,  asphalt  for 529 

784.  brick 540 

785.  specifications  for 541 

782.  compressed  asphalt-tile 539- 

791.  concrete  for 543 

795.  specifications  for 547 

770.  cross-slope  of 52T 

768.  definition  of 52T 

775.  dressing  of  stones  for 5291 

771.  foundation  of 528 

774.  granite  for 528 

779.  life  of  asphalt 530 

773.  materials  employed  for 528 

833.  price  of 576 

787.  of  artificial  stone 542 


854  INDEX. 


ARTICLE  PACK 

796.  Footpaths  of  artificial  stone,  specifications  for 548 

800.  gravel 552 

797.  tar  concrete 551 

797.  specifications  for 551 

772.  qualities  required 528 

909.  removal  of  snow  from 642 

780,  781.  Footpaths,  specifications  for  asphalt 530,  532 

769.  width  of  (Table  LXXXII) 508,  527 

777.  wood  for 529 

527.  Force  required  to  sustain  a  vehicle  upon  an  inclined  road 377 

1003.  Forfeiture  of  contract 676 

1030.  Form  of  agreement 694 

1039.  bid  or  proposal 693 

1031.  bond 703 

636.  borrow-pits  and  spoil-banks 422 

620.  contour  suitable  for  country  roadways 418 

620.  street  pavements 418 

1027.  contract  688 

721.  retaining- walls 486 

649.  side-slopes 427 

687.  tiles 456 

48.  traffic  census 19 

652.  Formation  of  embankments 430 

948.  specifications  for ; 661 

771.  footpaths 528 

801.  the  Central  Park,  N.  Y.,  walks 552 

862.  Foreman,  duties  of 597 

701.  Formula  for  calculating  area  of  water-way  of  culverts 465 

730.  thickness  of  retaining-walls  451 

1036.  Forster's  crusher 737 

452.  Foundation,  drainage  of 319 

452.  essentials  necessary  to  the  forming  of  good 319 

978.  excavation,  specifications  for 671 

240.  for  asphalt  pavements 174 

316.  brick  pavements 223 

771.  footpaths 528 

451.  pavements 319 

154.  stone  pavements 108 

456.  of  blast-furnace  slag  320 

457.  concrete 321 

154.  thickness  of  ...,, 108 

726.  retaining-walls 490 

186.  sand,  and  plank,  defects  of « 130 

455.  manner  of  forming 320 

185.  used  for  wood  pavements 130 


INDEX.  855 


ARTICLE  1'AGE 

959.  Fourth-class  masonry . .  665 

414.  France,   amount   of   material  used  to  replace  wear  of  broken-stone 

pavements 289 

contract  work  on  roads 615 

418,  865.          cost  of  maintaining  roads  in 291,  602 

355.                    methods  of  testing  the  qualities  of  broken  stone 259 

865.  national  roads  of 602 

road  commissioners  in 612,  617 

road  police  in 617 

taxes  in 618 

task- work  on  roads  in 615 

866.  French  system  of  highway  maintenance,  regulations  for  cantonniers 

(road  laborers) 604 

914.  Frequency  of  street  sprinkling 643 

521.  Friction,  resistance  of , 372 

507.  Frost,  effect  of,  upon  mortars 351 

411.                               on  roads 286 

D21.  Fruit-trees  and  roads  in  Saxony 649 

330.  Furnace  slag  for  bricks 233 

470.                                 concrete 327 

450a.                              paving 311 


G 

226.  Gas,  injurious  effects  of,  on  asphalt 164 

106.  tar 74 

1036.  Gates  crusher 737 

153.  Gauging  of  granite  blocks . , 1 07 

General  stipulations  applicable  to  all  contracts 672 

91a.  Gilsonite 41,  43 

104.  price  of 73 

450i.  Glass  pavement 315 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

€5.  Gneiss 27 

specific  gravity  of  (Table  XXIV)  97 

weight  of  (Table  XXIV). . 97 

•605.  Grade  on  mountain  roads 408 

1033.  Grader,  New  Era 724 

671 ,  1033.  Graders,  mechanical 444,  723 

222,  261.  Grades,  and  asphalt  pavements 160,  185 

899.  steam-rollers 275 

595.  tractive  power  of  horses .- 406 

596.  angles  of 406 


856  INDEX. 


ARTICLE  PAGE 

751.  Grades  at  street- intersections,  adjustment  of 507 

594.  definition  of 404 

595.  determination  of 40ft 

531.  effect  of,  upon  the  load  drawn 377 

609.  establishing  the 415, 

532.  loads  drawn  by  horses  on 377 

599.  maximum 407 

601.  suitable  for  different  paving  materials 407 

608.  methods  of  designating  (Table  LXI1) 414 

606.  minimum 413 

745.  of  city  streets  (Table  LXXXII) 500,  508- 

585.  on  curves 401 

847.  profit  of  eliminating 581 

608.  rise  in  feet  per  hundred 414 

608.  mile 414 

540.  steep,  objections  to 382 

166.  pavements  on Ill 

752.  transverse  of  street 509 

607.  undulating 41  j) 

947.  Grading,  definition  of , , 660 

947,  1018.          specifications  for 660,  682 

1033.  tools  for 711 

Grahamite  (Table  XlVa). 43 

63.  Granite,  abrasion  of 20 

64.  absorptive  power  of  (Table  V) 27 

70.  amount  used  for  street  purposes  in  1889  (Table  VII) 30 

443.  block,  artificial 308 

140.  pavement    102 

142.  advantages  of 102 

874.  amount  of  dirt  produced  by 624 

894.  area  cleaned  by  one  man. .    635 

877.  cost  of  cleaning 625 

172.  construction  (Table  XXVII) 118 

169.  maintaining 114 

143.  defects  of 102 

170.  manner  of  paying  for 114 

173.  specifications  for 120 

171.  blocks,  area  covered  by  one  ton  (Table  XXVI) 97 

65.  color  of 27 

816.  curb,  specifications  for 565 

65.  description  of 27 

774.  for  footpaths 528 

27.  life  of 11 

masonry,  weight  of  (Table  XXIV) 97 

167.  paving-blocks,  durability  of 113 


INDEX.  857 


ARTICLE  PAGE 

153.  Granite  paving-blocks,  gauging  of 107 

156.  laying  off 108 

73.                                             manufacture  of 31 

171.                                             number  of,  to  a  square  yard 117 

157.  ramming  of 109 

168.                                             wear  of 113 

144.                   quality  of 104 

69.                   resistance  to  crushing  of  (Table  VI) 29 

19.                   slipperiness  of 9 

69.  specific  gravity  of  (Table  VI) 29 

72.                   uses  of 81 

70,  71.            value  of,  used  for  street  purposes  in  1889  (Table  VII) 30 

69.                    weight  of  (Table  VI) 29 

650.  Grass  on  slopes 428 

1042.  Gratings  for  catch-basins 786 

Gratuitous  assistance  to  travellers 609 

131.  Gravel ...  95 

639.              and  sand,  shrinkage  of 423 

425.               character  of,  for  pavements 299 

381 .               core  for  broken-stone  pavements 270 

800.  footpaths 552 

428.              laying  of 300 

424.              pavements 299 

432.  cost  of  construction  (Table  XLIII) 301 

431.                                repairof 300 

428.                                sprinkling  of 300 

transverse  rise  for  (Table  LXIV) 418 

427.              preparation  of,  for  paving  purposes 299 

638.              shrinkage  of 423 

427.              size  of,  for  paving 299 

131.              Tomkins  Cove 95 

131.                                      analyses  of 96 

372,  461.      voids  in 267,  322 

812.               walks,  directions  for  their  construction 560 

801.  in  Central  Park,  New  York 552 

433.  weight  of 301 

with  clay,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

525.  Gravity,  effect  of  (Table  LII) 375 

Greenstone,  specific  gravity  of  (Table  XXIV) 97 

62.  Grinding  test 25 

44.  Gross  cost  of  pavements 16 

967.  Grouting,  specifications  for 667 

946.  Grubbing,  specifications  for 660 

1032.  tools  for .710 


858  INDEX. 


ARTICLE  PAGE 

50.  Guaranteeing  pavements 21 

738.  Guard  stones 494 

216c.  Gum  wood  blocks 155 

Gunpowder,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

760,  826.  Gutters 516,  571 

828.  brick,  specifications  for 572 

827.                       cobblestone,  specifications  for 571 

1042  -crossings  of  cast-iron 788 

in  Central  Park,  N.  Y 553 

694.  on  inclines,  protection  of , 461 

1018.  specifications  for 684 

151.  stone  block 105 

829.  -stones,  specifications  for 573 

H 

676.  Half- widths,  calculating  the 448 

325.  Hale  pavement ,  .  . . 232 

583    Halting-places 401 

323.  Halwood  paving-block 231 

362,  1036.  Hammers  for  breaking  stone 265,  734 

361.  Hand-broken  stone 265 

897, 1040.  -brooms,  kinds  of 636,  770 

1040.  -cart  used  by  street  patrol 774 

362,  1036.  -hammers 265,  734 

465.  -made  concrete 324 

1038.  -rammers,  price  of 761 

892.  sweeping  635 

89c.  Hard  bitumen .' 39 

59,  352.  Hardness  of  stones 24,  252 

1036.  Harrisburg  roller 755 

673.  Haul 445 

322.  Hayden  paving-block .  230 

423.  Heads  of  specifications  for  broken-stone  pavements 297 

173.  granite-block  pavements 120 

1027.  repairing „ ..  688 

262.  standard  Trinidad  asphalt  pavement 186 

213.  wood  pavement 144 

Heater  for  asphalt 769 

211.  Henson  wood  pavement 141 

1016.  Highway,  specifications  for  construction  of  a 680 

625.  Hillside  roads,  form  of  transverse  contour 420 

659.  Hillsides,  embankments  on , 436 

659.  retaining- walls  on 436 


INDEX.  859 


825.  Hollow  curbs  of  artificial  stone 570 

370,  1036.  Horse  power  required  for  stone-crushers ,, 267,  737 

397.  rollers,  defects  of  . .   274 

1036.  dimensions  of 752 

1036.  price  of 752 

work  of,  at  different  rates  of  speed  (Table  LVI) 379 

532.  Horses,  draught  of 377 

22.  falls  of,  kinds  and  causes 10 

410,  1044.         feet,  effect  of,  on  pavements 284,  797 

536.  loads  drawn  by,  on  grades  (Table  LVII) 379,  794 

maximum  velocity  unloaded  (Table  LIV) 378 

11,  12.  number  required  to  move  one  ton  on  different  pavements 

(Table  II) 6 

tractive  power  of,  at  different  velocities  (Table  LIII) 378 

534.  work  done  by 378 

1044.  Horseshoes  and  pavements 797 

78.  Hudson  River  bluestone 33 

473.  Hydraulic  cement 328 

472.  lime .  327 


I 

Ice,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV)  97 

104.  Imports  of  asphaltuni  into  the  United  States  in  1890 73 

212.  Improved  wood  pavements 142 

834.  Improvement  of  roads. 577 

842.  Improvements,  value  of 580 

835.  Improving  clay  roads 577 

837.          sand  roads 579 

850.  the  surface,  profit  of 583 

648.  Inclinations  given  to  side-slopes  in  different  materials 427 

699.  of  culverts 465 

691.  drains , 457 

527.  Inclines,  force  required  to  sustain  vehicles  on 377 

536.  loss  of  tractive  power  on 379 

power  required  to  haul  one  ton  up  different  (Table  LIX)  . .  383 

528.  pressure  of  vehicles  on 377 

694.  protection  of  gutters  on 461 

597.  tractive  power  required  in  descending 406 

991.  Incompetent  workmen,  dismissal  of 673 

790.  Increase  in  bulk  of  cement 543 

C38.  of  excavated  rock 423 

766.  Increasing  width  of  carriageway  at  street-intersections 525 

1020.  Indemnification  for  patent  claims  686 


SCO  IXDEX. 


ARTICLE  PAGE 

1021.  Indemnity  bond 68& 

4500.  India-rubber  pavement 317 

461-464.  Ingredients  for  concrete,  proportions  of 322 

1042.  Inlet-traps  for  sewers 7Sl> 

997.  Inspectors 674 

765.  Instructions  regarding  street  profiles 523- 

1028.  to  bidders 68£ 

864.  roadmen 600- 

566.  Instruments  employed  in  reconnoitring 391 

3.  Interests  affected  in  the  selection  of  pavements 2- 

578.  Intermediate  towns 398 

985.  Interpretation  of  specifications 672- 

152.  Intersection,  paving  at  street 105 

450.  Iron  and  wood,  combinations  of 311 

cast,  crushing  resistance  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

984.  specifications  for 672 

weight  of  (Table  XXIV) 97 

780.  Iron  curb 532- 

450.  pavements 311 

329.  paving-bricks 233- 

708.  pipe-culverts 471 

weight  of  (Table  LXXIII) 472; 

1006.  Iron  pitch 54 

161.  Iron,  slag,  and  Portland  cement  for  joint-filling 110 

wrought,  crushing  resistance  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

983.  specifications  for 671 

weight  of  (Table  XXIV) 97 

438.  Italian  trackways 306- 


J 

442.  Jasperite 307" 

319.  Joint-filling  for  brick  pavements 225- 

159.  stone  blocks 109 

192.  wood  pavements 134 

161,  319.  Murphy's  grout 110,  225 

161.  of  Portland  cement  and  iron  slag  for  pavements 110 

191.  Joints  in  wood  paving,  width  of 134 

706.  of  pipe-culverts 467 

441.  Junctions  of  trackways , 307 

152.  paving  at  street 105> 


INDEX.  861 


K 

ARTICLE  PAGE 

216c.  Karri  wood  pavement 154 

Keeping  tools  in  repair. . . . , 598-610 

99<7.  Kentucky  bituminous  sandstone 53 

€82.  Kinds  of  drainage 455 

796a.  Kosmocrete 551 

188.  Kyanizing 132 


881.  Laborers'  wages  in  Baltimore 630 

SIS.  Berlin ; 628 

•879.  Paris 629 

100,  lOOp.  Lake  pitch 53-59 

100,  lOOa,  lOOp.  Land  pitch 53,  54,  59 

€16.  Land,  width  of,  appropriated  for  road  purposes 416 

384.  Layers  of  broken  stone,  thickness  of , . . . .  271 

965.  Laying  masonry  in  freezing  weather,  specifications  for 666 

466.  of  concrete 324 

156.  granite  blocks 108 

428.  the  gravel 300 

Lead,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

837.  Leaves  on  sandy  roads , 579 

645.  Length  and  angle  of  slopes  (Table  LX VI) 425 

849.  decreasing  the,  profit  of 582 

$32.  of  culverts,  to  ascertain 654 

level  road  equivalent  to  an  inclined  road  (Table  LIX) 383 

148.  paving-blocks 105 

€87.  tiles 456 

€08.  Level  stretches 41 4 

572.  Levels , 392 

779.  Life  of  asphalt  footpaths 530 

27.  pavements 11 

27.  brick  pavements 11 

27,  167.        granite-block  pavements 11,  113 

•37.  limestone-block  pavements 11 

444.  plank  roads 308 

27.  sandstone  pavements 11 

27,  193.        wood  pavements 11,  135 

85.  Ligonier 37 

472.  Lime,  common 327 

472.  hydraulic 327 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 


862  INDEX. 


ARTICLE  PAGE 

63.  Limestone,  abrasion  of 26 

64.  absorptive  power  of  (Table  V) 27 

amount  produced  for  street  purposes  in  the  United  States 

in  1890  (Table  XIII) 37 

996.  bituminous 44,  51 

QQd.  analysis  of 51 

99/.  how  used 51 

27.  block  pavements,  life  of 11 

82.  description  of 35 

84,  165.  paving,  experience  with 36,  111 

resistance  to  crushing  of  (Table  XII) 37 

specific  gravity  of  (Table  XII) 37 

83.  uses  of 36 

value  of,  used  for  street  purposes  in  1890  (Table  XIII). .  37 

weight  of  (Table  XII) 37 

Limestones,  bituminous,  specific  gravity  of  (Table  XXIV) 97 

Liquid  bitumen 47 

specific  gravity  of  (Table  XXIV) 97 

weight  of 97 

992.  Liquors,  spirituous 678 

93c,  99tf.  Lithocarbon 43,  51 

715.  Live  loads  and  bridges „ 480 

81.  Liverpool  pavements 12 

400.  Loaded  vehicles,  pressure  of 275 

536.  Loads  drawn  by  horses  on  grades  (Table  LVII) 380,  794 

439.  moved  on  trackways 307 

639.  Loam,  shrinkage  of 423 

592.  Location  final 404 

555.  of  country  roads .'  389 

447.  Log  roads 310 

880.  London,  pavements 630 

880.  street  cleaning  in 630 

858.  Lose  stones  on  roads 588,  607 

669.  Loosening  earth 444 

671.  by  machinery 444 

1009.  Loss  and  damage 678 

581.  of  height 400 

536.  tractive  power  on  inclines 379 

M 

434.  Macadam,  bituminous 301 

345.  concrete 250 

343.  pavements 249 

345.  analyses  of 250 

1037.  roads,  tools  employed  for  maintenance  of 761 


INDEX.  863 


ARTICLE  PAGE 

1 018.  Macadamizing,  specifications  for 682 

1036.  tools  for 734 

345.  MacAdam's  method,  defects  of .- 250 

364.  Machine-broken  stones,  objections  to 266 

356a.                  for  cementation  test  of  stone 260 

492.                   for  testing  cement 340 

511.                    -mixing  of  mortar  and  concretes  vs.  hand-mixing 358 

Machines  for  mixing  concrete,  price  of 768 

418.  Maintenance,  broken-stone  pavements,  cost  of 290 

36.                            considerations  concerning 14 

860.                          costof 592 

285.                                        asphalt  and  coal-tar  pavements 204 

852.  definition  of 585 

853.  necessity  of 585 

265,                           of  asphalt  pavements  by  contract 193 

233.                                                                 cost  of 168 

836.                               clay  roads 578 

857.                                country  roads 586 

841.                               earth  roads,  cost  of 580 

169.  granite-block  pavements,  cost  of 114 

macadam  roads,  tools  employed  for 734 

403.                               steam-rollers,  cost  of 276 

865.                               the  French  roads 602 

206.                              wood  pavements,  cost  of 139 

214.                                                             by  contract 147 

856.                           systems  of 586 

88«,  93tf,  96d,  98a.  Maltha 39,  43,  46,  49 

1025.  Manhole  covers,  etc. ,  alteration  of 687 

405.  Manner  of  applying  the  roller 280 

318.                      laying  brick  pavements 223 

1 70.  paying  for  granite-block  pavements 114 

415.                      restoring  the  thickness  of  broken-stone  pavements 289 

73.  Manufacture  of  granite  paving-blocks 31 

114.                                paving-brick 79 

570.  Map 392 

657.  Marshes,  embankments  across. 433 

956.  Masonry,  first-class , 664 

959.                     fourth-class 665 

965.                     laying,  in  freezing  weather,  specifications  for 666 

957.  second-class 664 

956.                     specifications  for 664 

958.  third-class 665 

weight  of  (Table  XXIV) 97 

405.  Massachusetts  Highway  Commission,  rules  for  rolling 278 

356#.                                                                  tests  of  stone  by 260 


866  INDEX. 


ARTICLE  PAGE 

886.'  New  York,  street-cleaning  in 632 

43.  Noisy  pavements,  objections  to 16- 

93.  Nomenclature  of  asphaltum 42 

866.  Nomination  of  cantouniers 605 

1004.  Non-completion,  damages  for 677 

989.  Notice  to  contractors 672 

450;.  Novaculite , 315 

Number  of   cubic  yards  of    broken   stone  required   for    different 

widths  (Table  XL)  271 

171.  granite  blocks  to  a  square  yard  (Table  XXVI) 117 

11.                           horses  required  to  move  one  ton  on  different  pavements.       6 
183.  wood  blocks  to  a  square  yard 129 


O 

1.  Object  of  pavements 1 

618.  raising  the  centre  of  roads 418 

222.  Objections  to  asphalt  pavements 159 

137.  .     Belgian  block  pavements 101 

134.  cobblestone  pavements 99 

588.  crookedness 403 

43.  dusty  pavements 16 

143.  granite-block  pavements 102 

397.  horse  rollers 274 

347.  Macadam  -pavements 250 

364.  machine-broken  stones 260 

43.  noisy  pavements 16 

540.  steep  grades 382 

344.  Telford  pavements £49 

395.  traffic  consolidation 273 

695.  water-breaks 461 

179.  wood  pavements 125 

591.  zigzags 403 

17.  Observations'  in  London  on  slipperiness  of  pavements 8 

16.  United  States  on  slipperiness  of  pavements 8 

92.  Occurrence  of  asphaltum 41 

952.  Off- take  ditches,  specifications  for 6(53 

10436.  Oil  for  sprinkling  roads 795 

435.  Old  asphalt  and  broken  stone * 302 

1023.          materials,  disposal  of 686 

986.  Omissions  in  specifications 672 

368.  Operating  stone  crushers,  cost  of 2<U> 

403.  steam-rollers,  cost  of 276 

38.  Opinions,  prevailing,  concerning  pavements 15 

862.  Organization  of  road  force 596 


INDEX.  867 


ARTICLE  PAGE 

862.  Organization  of  road  force  accounts 599 

862.  county  engineer.   599 

863.  chief  foreman 597 

862.  foremen.   . .   597 

862.  number  of  men  required 596 

862.  roller 598 

862.  snow 599 

862.  storage  and  delivery  of  broken  stone 599 

862.  team  labor  and  materials/ 598 

862.  tools 598 

91.  Origin  of  bitumen   „ 41 

687.  Outlets,  drain ,  protection  of 456> 

673,  999.  Overhaul,  how  measured 445,  674 

P 

735.  Parapets 49S 

735.  height  of 493 

964.  specifications  for 666 

735.  thickness  of. .-.. 493 

879.  Paris,  street-cleaning  in 629- 

1000.  Partial  payments 675- 

1020.  Patent  claims,  indemnification  for 686 

880.  Patrol  system  in  London 630 

29.  Pavement,  the  cheapest 11 

9.  Pavements,  adaptability  of 4 

874.  amount  of  dirt  produced  by  different 624 

1044.  and  horseshoes 797 

10.  and  popular  prejudice 5> 

1047.  annual  cost  of 806- 

450/,  786.  artificial  stone 314,  542 

126.  Belgian  block  101 

304.  brick 219 

335.  broken-stone , 246 

346,  advantages  of . '. 250 

396.  rolling 274 

393.  compa  ting  the  stone 273 

,093.  by  rollers  drawn  by  horses. . .  .  273 

393  by  steam-rollers 273 

393.  the  traffic 273 

347.  defects  of 250 

380.  failure  of  thin 270 

421.  in  Bridgeport,  Conn 292 

420.  Chicago 292 

.;19.  England 291 

4^3.  loss  of  thickness,  average  annual 289 


866  INDEX. 


886. '  New  York,  street-cleaning  in 032 

43.  Noisy  pavements,  objections  to 16 

93.  Nomenclature  of  asphaltuin 42 

866.  Nomination  of  cantonniers 605 

1004.  Non-coinpletion,  damages  for 677 

989.  Notice  to  contractors 672 

450;.  Novaculite , 315 

Number  of   cubic  yards  of    broken   stone   required   for    different 

widths  (Table  XL)  271 

171.  granite  blocks  to  a  square  yard  (Table  XXVI) 117 

11.                           liorses  required  to  move  one  ton  on  different  pavements.       6 
183.  wood  blocks  to  a  square  yard 129 


O 

1.  Object  of  pavements 1 

618.  raising  the  centre  of  roads 418 

222.  Objections  to  asplialt  pavements 159 

137.  .     Belgian  block  pavements 101 

134.  cobblestone  pavements 99 

588.  crookedness 403 

43.  dusty  pavements 16 

143.  granite-block  pavements 102 

397.  horse  rollers 274 

347.  Macadam  -pavements 250 

364.  machine-broken  stones 266 

43.  noisy  pavements 16 

540.  steep  grades 382 

344.  Telford  pavements 249 

395.  traffic  consolidation 273 

695.  water-breaks 461 

179.  wood  pavements 125 

591.  zigzags 403 

17.  Observations"  in  London  on  slipperiness  of  pavements. 8 

16.  United  States  on  slipperiness  of  pavements 8 

92.  Occurrence  of  asphaltum 41 

953.  Off-take  ditches,  specifications  for 603 

10436.  Oil  for  sprinkling  roads 795 

435.  Old  asphalt  and  broken  stone 1 302 

1023.  materials,  disposal  of 686 

986.  Omissions  in  specifications 672 

368.  Operating  stone  crushers,  cost  of 266 

403.  steam-rollers,  cost  of 276 

38.  Opinions,  prevailing,  concerning  pavements 15 

862.  Organization  of  road  force 59fr 


INDEX.  867 


ARTICLE  PAGE 

862.  Organization  of  road  force  accounts 599 

862.  county  engineer.   599 

862.  chief  foreman 597 

862.  foremen.   . .  . 597 

862.  number  of  men  required 596 

862.  roller 598 

862.  snow 599 

862.  storage  and  delivery  of  broken  stone 599 

862.  team  labor  and  materials/ 598 

862.  tools 598 

91.  Origin  of  bitumen   „ 41 

687.  Outlets,  drain,  protection  of 450 

67o,  999.  Overhaul,  how  measured 445,  674 

P 

735.  Parapets 49S 

735.  height  of 493 

964.  specifications  for 666 

735.  thickness  of 493 

879.  Paris,  street-cleaning  in 629' 

1 000.  Partial  payments 675- 

1020.  Patent  claims,  indemnification  for 686- 

880.  Patrol  system  in  London 630 

29.  Pavement,  the  cheapest 11 

9.  Pavements,  adaptability  of 4 

874.  amount  of  dirt  produced  by  different 624 

1044.  and  horseshoes 797' 

10.  and  popular  prejudice 5> 

1 047.  annual  cost  of 806 

450/,  786.  artificial  stone 314,  542 

126.  Belgian  block   101 

304.  brick 219 

335.  broken-stone 246 

346.  advantages  of . '. 250 

396.  rolling 274 

393.  coinpa  ting  the  stone 273 

,°93.  by  rollers  drawn  by  horses. .  .  .  273 

393.  by  steam-rollers „ 273 

393.  the  traffic 273 

347.  defects  of 250 

380.  failure  of  thin 270 

421.  in  Bridgeport,  Conn.    , 292 

420.  Chicago 292 

-!19.  England 291 

413.  loss  of  thickness,  average  annual 289 


868  INDEX. 


.ARTICLE  PAOB 

417.  Pavements,  broken-stone,  recoating,  when  it  should  be  done 290 

433.  specifications  for 297 

383.  spreading  the  stone 270 

378.  thickness  of 269 

384.  the  layers 271 

409.  wear  of 284 

39.  care  of : 14 

201,  208,  216.       cedar-block 137,  140,  151 

40.  cleansing  of 15 

134.  cobblestone 99 

compai  ative  merit  of  (Table  IV) 21 

28.  considerations  concerning  cost  of 11 

216e.  cottonwood  blocks 155 

10.  desirability  of 5 

55.  destruction  of 22 

23.  durability  of 10 

32.  economic  benefit  of  good 13 

410  effect  of  atmospheric  changes  on 284 

451.  foundations 319 

460.  character  of  concrete  for 322 

457.  concrete  for 321 

140.  granite-block 102 

44.  gross  cost  of 16 

oO.  guaranteeing , 21 

2160.  gum  blocks 155 

325.  Hale  brick 232 

325.  Hale  system , 232 

323.  Hal  wood  system 231 

322.  Hayden  system 230 

211c  Henson's  system 141 

3.  interests  affected  in  the  selection  of 2 

load  drawn  by  a  horse  on  different  (Table  LVII) 380 

2160.  Karri  wood 154 

345.  macadam,  analyses  of 250 

999.  measurement  of 675 

209.  mesquite  block 141 

1 .  object-  of ,       1 

292.  of  asphalt  block 208 

208.  cedar  blocks 140 

281.  coal-tar 203 

281.  and  asphalt 203 

424.  gravel 299 

432.  cost  of  construction.   301 

450.  iron 311 

31.  Liverpool 11 


INDEX.  869 


ARTICLE  PAGE 

209.  Pavements  of  mesquite-block 141 

166.  on  steep  grades Ill 

451.  permanence  of. 819 

2l6d.  pine  block 155 

2.  qualities  of  good 1 

216/.  redwood  block 155 

34.  relative  economies  of 14 

15.  safety  of 7 

454.  sand  as  a  foundation  for 820 

14.  serviceability  of. 7 

451.  stability  of . 319 

280.  vulcanite 202 

56.  waste  of  money  in  opening 23 

152.  Paving  at  street-junctions 105 

148.  blocks,  length  of 105 

73.  makers,  wages  of 32 

73.  manufacture  of  granite 31 

71.  price  of 30 

146.  shape  of 104 

146.  size  of 104 

147.  width  of 104 

63.  brick,  abrasion  of 26 

64,  119.  absorptive  power  of  (Table  V) 27,  86 

1 17.  characteristics  of  good 82 

111.  clayfor 78 

114.  manufacture  of 79 

prices  of  (Table  XXI) 86 

1 19.  resistance  to  crushing  of  (Table  XXIV) 86,  97 

size  of 86 

119.  specific  gravity  of  (Table  XXI) 86,  97 

119.  weight  of  (Table  XXI) 86 

58  material,  selection  of 24 

106.  pitch 74 

1005.  Payment  of  claims 677 

1013.  workmen 679 

1 000.   Payments,  partial.   675 

1015.  when  made 679 

Peat,  weight  of  (Table  XXIV) 679 

103«.  Penetration  tests  of  bitumen 62 

421.   Permanence  of  pavements 319 

506.  Permeability  of  mortars 351 

Peruvian  asphaltum  (Table  XI Va) 351 

5 1 9.  Penetration,  resistance  of 3(i? 

88a,  91.  Petroleum 39,  41 

07/>.  residuum    47 


INDEX. 


ARTICLE  PAGK 

97rf.  Petroleum  residuum,  specification  for 49 

976.                                          test  for 47 

specific  gravity  of  (Table  XXIV) ".  -. 97 

weight  of  (Table  XXIV) ; 97 

90,  90a.   Petrolene '. 40 

1 33.  Philadelphia,  cobblestone  pavements  in 99 

887.                             street-cleaning  in  •„ 683 

4 1 5.  Picks  on  steam-rollers,  objectionable 289 

9M.  Piles,  specifications  for 671 

2 I6d.  Pine  wood  paving  blocks ioo 

706.  Pipe-culveits 467 

971.  specifications  for 603 

iron,  dimensions,  weight,  and  price  of  (Table  LXXIII) 473 

707.  vitrified,  dimensions,  weight,  and  price  of  (Table  LXXI) 471 

Pipes,  discharging  capacity  of  (Table  LXXVIII) 4r,g 

433.   Pit-gravel,  weight  of 301 

bS/«,  93.   Pitch,  mineral 39,  43 

106.                        paving 74 

specific  gravity  of  (Table  XXIV) 97 

weight  of 97 

656.  Plains,  embankments  over 483 

186.  Plank-and-sand  foundation,  defects  of 130 

444.  roads 308 

445.  construction  of 308 

446.  cost  of 310 

446.                       life  of 310 

995.  Plans  and  specifications,  deviations  from 673 

1033.  Ploughs,  cost  of  operating 711 

1033.                   for  grading,  price  of 711 

1033.                    quantity  of  material  loosened  with 711 

966.  Pointing,  specifications  for 667 

59.  Porosity  of  paving  materials , . . .  24 

Porphyry,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

1035.  Portable  boilers,  price  of 733 

1036.  engines,  price  of 747,  748 

475.  Portland  cement 329 

476.  characteristics  of 331 

476.                                contraction  of i . .  332 

509.                               English,  specifications  for 357 

476.                                expansion  of 332 

476,  fineness  of 331 ,  335 

476.                               specific  gravity  of 332 

972.  specifications  for 669 

476.                                tensile  strength  of 332 


INDEX.  871 


ARTICLE  PAGE 

477.  Portland  cement,  tests  for 332 

47»S  501.  weight  of 331,  346 

10.  Popular  prejudice  and  pavements 5 

518.  Power  required  to  draw  wheels  over  obstacles 366 

haul  one  ton  up  different  inclines  (Table  LIX) . . .  383 

1008.               to  suspend  work 678 

U9/.  Preparation  of  the  bituminous  limestone 51 

99*7.                              bituminous  sandstones 52 

424.                               gravel  for  paving 299 

516.                              roadbed,  specifications  for 362 

lOOe.                              Trinidad  asphaltum 55 

990.  Preservation  of  engineer's  marks 673 

188.                               wood 131 

Pressed  brick,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of 97 

weight  of 97 

400.  Pressure  of  loaded  vehicles 275 

397.                        rollers 274 

528.                        vehicles  on  inclines 377 

38.  Prevailing  opinions  concerning  pavements 12 

334e.  Price  of  paving-brick 245 

1014.  Prices  in  contract 679 

104.  of  asphaltum  in  New  York  in  1893 73 

161.                    bituminous  cement , 110 

104.                    California  bituminous  rock 73 

833.                    footwalk  materials , 576 

104.                   gilsonite 73 

71.                    granite  blocks 30 

1033.                    mechanical  graders 722 

paving-brick  (Table  XXI) 87 

129.                   sand 94 

367,  368.           stone-crushers 266 

1040.                    tools  for  cleaning 770 

1032.  clearing 710 

1033.  grading 711 

1032.                                    grubbing....... 710 

1036.  macadamizing 734 

1037.  maintenance 761 

675.  Prismoidal  formula 447 

8.  Problem  involved  in  the  selection  of  pavements 4 

104.  Production  of  bituminous  rock  in  the  United  States  in  1893  (Table 

XVIII) 73 

bluestone  in  the  United  States  in  1889  (Table  XI) 35 

granite  in  the  United  States  in  1889  (Table  VII) .  30 

limestone  in  the  United  States  (Table  XIII) 37 


872  INDEX. 


ARTICLE  %  PAGE 

104.  Production  of  sandstone  for  street  purposes  in  1889  (Table  X) 35 

574.  Profile ...  395 

593.  construction 404 

765.  Profiles,  street 523 

849.  Profit  of  decreasing  the  length 582 

847.  eliminating  unnecessary  grades 581 

850.  improving  the. surface 583 

1003.  Progress  of  work 676 

389.  Properties  of  binding  adopted  by  the  French  engineers 272 

100.                          Trinidad  asphaltum 54 

426.  Proportion  of  clay  to  gravel 299 

716.  Proportioning  of  bridges 480 

461,  462.  Proportions  of  ingredients  for  concrete 322 

464.                                                          usual  for  concrete 323 

253.  materials  used  in  the  manufacture  of  Trinidad 

asphalt  pavements 182 

724.                                     retaining-walls 486 

1029.  Proposal,  form  of 693 

689.  Protection  of  drain-outlets 457 

694.                          gutters  on  inclines 460 

1006.                          persons  and  property 677 

734.                          roads 492 

927.                          trees 651 

31.  Public  bodies  and  economy 12 

Q 

314.  Quality  of  bricks    222 

830.  cross-stones 573 

776.  flagstones 529 

144.  granite 104 

425.  gravel  for  roads 299 

993.  materials 673 

459.  materials  for  concrete 322 

495.  mortar 342 

126.  sand ,..     94 

155.  for  cushion-coat 108 

349,  351.  stone  for  broken-stone  pavements 251 ,  ?52 

459.  concrete 321 

497.  water  for  mortar 343 

187.  wood  for  paving 131 

2.  Qualities  of  good  pavements 1 

780.  require'd  in  footpaths 530 

382.  Quantity  of  broken  ston*  required  per  mile  for  different   widths 

(Table  LX) 270< 


IXDEX.  873 


ARTICLE  PAGE 

1033.  Quantity  of  material  loosened  with  ploughs 711 

464.                        materials  required  for  one  cubic  yard  of  concrete 323 

128.                         sand  required  for  bedding-blocks 94 

336.                         stone  broken  by  hand 246 

367,  1036.                                            machines 266,  734 

463.                          water  required  for  concrete , . .  323 

498.                                                         mortar 343 

913.                                                         street  sprinkling 643 

371.  Quarrying  stone,  cost  of  (Table XXX), 267 

Quartz,  weight  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

67.  Quartzite 28 

487.  Quick-  and  slow-setting  cements,  definition  of 337 

B 

1033.  Rails,  weight  of 720 

19.  Rain  and  asphalt  pavement 9 

411.  effect  of,  on  roads 284 

699.  Rainfall,  amount  of 464 

466.  Rammers  for  concrete,  dimensions  of 824 

1038.  hand,  price  of 762 

1038.  weight  of 762 

466.  Ramming,  amount  required  for  concrete 324 

466.  concrete 324 

158.  granite-blocks 109 

897.  Rattan  brooms 636 

61.  Rattler  tests 25 

417.  Recoating  broken-stone  pavements,  when  it  should  be  done 290 

558.  Reconnoissance 389 

834.  Reconstruction  of  roads 577 

863.  Records 600 

189.  Rectangular  wood  blocks 133 

216/.  Redwood  paving  blocks , 155 

95.  Refined  asphaltum 44 

lOOw.  specific  gravity  of , 58 

751.  Refuges  at  street-intersections 507 

873.  Refuse,  amount  collected  from  streets  (Table  LXXXVI) , 623 

899.  disposal  of 636 

866.  Regulations  for  cantonniers 604 

:-54.  Relative  economies  of  pavements 14 

832.  Relaying  bridge-stones,  specifications  for 575 

900.  Removal  of  snow 637 

907.  from  footpaths 639 

902.  in  Milan 637 


g74  INDEX. 


ARTICLE 

861.  Repair  of  broken-stone  pavements 596 

431.  gravel  pavements • 30u 

1024.  Repairs,  security  retained  for 687 

1026.  Repaving,  specifications  for 687 

862.  Requisitions  for  tools,  etc 599 

521.  Resistance  of  friction 372 

525.  gravity  (Table  LII) 375 

519.  penetration 367 

to  crushing  of  basalt  (Table  XXIV) 97 

bluestone  (Table  IX) 35 

bricks  (Table  XXIV) 97 

cast  iron  (Table  XXIV).. 97 

chalk  (Table  XXIV) 97 

common  hard  brick  (Table  XXIV) 97 

concrete  (Table  XXIV) 97 

<J9.                                                granite  (Table  VI) 29 

lead  (Table  XXIV) 97 

85.                                                  Ligonier"  granite" 37 

limestones  (Table  XII) 37 

119.  paving-bricks 86,  88,  97 

pressed  bricks  (Table  XXIV) 97 

81.                                                sandstones  (Table  IX) 34 

soft  brick  (Table  XXIV) 97 

steel  (Table  XXIV) 98 

•  Stourbridge  brick  (Table  XXIV) 97 

87.                                                  trap-rocks  (Table  XIV) 38 

wood  (Table  XXII) 92 

wrought-iron  (Table  XXIV)    97 

517.                         traction 366 

on  different  road  surfaces  (Table  L) 372 

721.  Retaining-walls 486 

728.                               and  springs 491 

726.  dry-stone 490 

727.  failure  of 491 

725.  formof 490 

730.  formula  for  thickness  of 491 

726.  foundation  of 491 

730.  minimum  thickness  of 491 

659.  on  hillsides 436 

724.  proportions  of 486 

954.  specifications  for 663 

733.  where  they  should  be  built 492 

90,  90a.  Retine . . . . 40 

1030    Revolving  stone  screens,  price  of 640 

996    Right  reserved  to  alter  details 673 


INDEX.  875 


ARTICLE  PAGE 

1036.  Ring  gauge 734 

953.  Kip-rap,  specifications  for 663 

Rise,  amount  of  transverse  (Table  LXIV) 418 

739.  River-banks,  roads  along 494 

862.  Road  force,  organization  of 59~3 

1033.  -leveller,  price  of 726 

1033.  use  of 726 

1033.  machines,  price  of 622 

-surface,  resistance  to  traction  on  different  (Table  L) 372 

1036.  Roadbed  roller,  form  of 735 

1036.  price  of 735 

1036.  weightof 735 

516.  specifications  for  preparation  of 362 

864.  Roadmen,  instructions  to : 600 

862.  number  required , 596 

584.  Roads,  alignment  of 491 

739.  along  river-banks 494 

739.  the  seashore , 494 

448.  charcoal  , 310 

835.  clay 577 

447.  corduroy 310 

555.  country,  location  of 389 

846.  defects  of  existing 581 

682.  drainage  of 455 

865.  French,  maintenance  of 602 

424.  gravel 299 

447.  log « 310 

865.  national,  of  France 602 

number  of  acres  required  per  mile  for  different  widths  of 

(Table  LXIII) 417 

444.  plank   308 

734.  protection  of  . .  • 492 

834.  reconstruction  of 577 

837.  sand 579 

^25.  transverse  contour 420 

D19.  trees  on 648 

•611.  width  of 416 

660.  Roadways  on  rock-slopes 488 

618.  transverse  contour  of 418 

661 .  Rock-cliffs,  manner  of  forming  roads  along 439 

662.  excavations « 441 

664.  cost  of 443 

1035.  tools  for , .  622 

639.  increase  in  bulk  of 423 

<tt>2.  quantity  of,  loosened  by  blasting 441 


876  INDEX. 


ARTICLE 

660.  Rock  slopes,  roadways  on  .......................................  4^8 

86.  Rocks,  trap  .........................................  ...........     38 

397.  Rollers,  horse,  defects  of  .........................................   274 

1036.  dimensions  of  .....................................  752 

3  036.  price  of  .........................  ,  ................  752 

397.  pressure  of  .............................................  274 

396.  steam,  advantages  of  ....................................   274 

401.  area  rolled  per  day  ..............................     27»i 

1036.  dimensions  of  ...................................   756 

405.  manner  of  applying  ..............................  286 

404.  speed  of  ...............................    .........  277 

404.  Rolling,  amount  required  for  broken-stone  pavements  ..............  277 

406.  cost  of  ....................   ............................  286. 

453.  foundations  ............................................  319 

520.  resistance  of  wheels  ...........................   .......  37  1 

Roman  cement,  specific  gravity  of  (Table  XXIV)  ..................     97 

weight  of  (Table  XXIV)  .........................     97 

473.  Rosendale  cement  ...............................................  328 

973  specifications  for  ...............................   669 

tests  for  .......................................  669 

473.  weight  of  .......................................  329 

26.  Roughness  and  durability  ........................................     11 

182.  Round  wood  blocks  .............................................  129 

576.  Route,  principles  to  be  observed  in  final  selection  of  ...............  396, 


S 
15.  Safety  of  pavements  ................................  ...........       7 

907.  Salt  used  for  the  removal  of  snow  ..................  ..............  639 

994.  Samples  of  materials  ............................................  67:i 

1  23.  Sand  ........................................  .  .................     93 

639.  and  gravel  ,  shrinkage  of  .  ..................................  423 

454.  as  a  foundation  for  pavements  ..............................  320 

126.  cleanness  of  ..............  '.  .........................  .  ......     JM 

381  .  core  for  broken-stone  pavements  ............................  270- 

3170.       '  cushion  .......................................  ...........  223 

475.  effect  of,  on  Portland  cement  ..............................   329 

504.  size  of  grain  on  strength  of  mortar  (Table  XLVIII).  .  350 

127.  for  concrete  ..........................................  .....     04 

155.  cushion-coat  of  stone  blocks  ............................  108 

,~»04.  mortar,  fineness  of  .....................................  34  7 

453.  foundations,  defects  of  .....................................  31  <> 

454.  manner  of  forming  ............................  320 

496.  in  mortar  .................................................  342 

223.  injurious  effects  of,  on  asphalt  pavement  ....................  160 


INDKX.  877 


ARTICLE  PAGE 

3  29.  Sand,  price  of 94 

126.             quality  of 94 

128.             quantity  required  for  bedding  block 94 

road,  load  drawn  by  a  horse  on  (Table  LVII) 380 

837.            roads,  improving  of 578 

837.                        treesof 569 

1 25.  sharpness  of 94 

1*3.             size  of,  for  paving  purposes  93 

504.                           sieves  for  sifting  (Table  XL1X) 350 

specific  gravity  of  (Table  XXIV). 98 

974.             specifications  for , 669 

126.  to  test 94 

124.            use  of 93 

916a.           to  prevent  slipping ' 646 

127.  462.     voids  in 94,  322 

130.  weight  of  (Table  XXIV) 94,  98 

127.            with  clay   <J4 

64.  Sandstone,  absorptive  power  of  (Table  V) 27 

79.                       amount  produced  for  street  purposes  in  1889 35 

analysis  of  (Table  VIII) 33 

99^.                      bituminous,  in  America 52 

99^.                                               Europe 52 

102.                                            analysis  of 61 

99*7.                                            preparation  of 52 

164,  172.  block  pavements,  cost  of  construction Ill,  117 

79.                       commercial  names  of 34 

74.                       description  of 32 

27.                       pavements,  life  of 11 

81.                       resistance  to  crushing  of  (Table  IX) 34 

81.                       specific  gravity  of  (Table  IX) 34 

79.                       value  of,  used  for  street  purposes  in  1889  (Table  X) 35 

weight  of  (Table  IX) 34 

182.  Sapless  cedar  blocks 129 

1036.  Scarifiers 758 

1040.  Scoop  used  by  street  patrol. 775 

670,  1033.  Scrapers  '. 444,  713 

1033.                            capacity  of. 713 

1033.                           cost  of 713 

1040.  Scraping-machines 773 

839.                                    improper  use  of 579 

839.                                     on  earth  roads 579 

350,  387.  Screening  the  broken  stone 251,  272 

739.  Seashore,  roads  along 494 

916.                    water  for  street  sprinkling 645 

957.  Second-class  masonry 664 


878  INDEX. 


ARTICLE  PAG  HI 

1054.  Security  retained  for  repairs 087 

575.  Selection  of  bridge  sites 81)5 

3.                         pavements,  interests  affected  in  the 2 

58.                         paving-material 24 

922.                         trees G4(J 

Serpentine,  specific  gravity  of  (Table  XXIV) <j7 

weight  of  (Table  XXIV) <j7 

41.   Service  of  pavements,  cost  of 15 

14.  Serviceability  of  pavements 7 

821.  Setting  curb,  specifications  for 567 

476.                of  Portland  cement 332 

937.                stakes  for  curb 657 

640.  Settlement  of  earth ,   423 

1041.  Sewer  inlet-traps 787 

1022.  Sewers,  right  to  construct 686 

Shales,  specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

313.  Shape  of  bricks 222 

357.                  stone  for  broken-stone  pavements 265 

146.                             paving-blocks 104 

182.                   wood  paving-blocks , 129 

125.  Sharpness  of  sand 94 

501.  Shearing  strength  of  mortar  (Table  XLVI) 3-16 

132.   Shingle  . . '. 96 

specific  gravity  of  (Table  XXIV) 98 

weight  of  (Table  XXIV) 98 

670,  1033.  Shovels 444,  71 1 

639.  Shrinkage  of  clay 423 

639.                           earth 423 

639.                          gravel 423 

639.                                      and  sand : . .  423 

639.                          loam 423 

639.                          vegetable  soil 423 

692.  Side  ditches 459 

649.  Side  slopes,  form  of 427 

648,  650.                 inclination  of 427 

654.                         of  embankments .• 432 

930.                        staking  out 652 

Sidewalks,  average  width  of,  in  various  cities  (Table  LXXXII) 508 

504.  Sieves,  size  of,  for  sifting  sand  (Table  XLIX) 350 

686.  Silicious  soils,  drainage  of 455 

687.  Silt  basins 45C 

Sinking  fund  that  with  compound  interest  will  amount  to  $1  at  the 

end  of  a  term  of  years  (Table  XC) 803 

1046.  Sinking  funds 806 


INDEX.  879 


ARTICLE  PAGE 

67.  Sioux  Falls  stone 28 

313.  Size  of  bricks 222 

131.  gravel  for  paving 95 

123.  sand  for  paving  purposes 94 

504.  sieves  for  testing  sand  (Table  XLIX) 350 

367,  368.        stone-crushers 266,  740 

357.  for  broken-stone  pavements t 265 

459.  concrete  322 

146.  paving-blocks 104 

182.  wood  paving-blocks 129 

549.  wheels 386 

4506.  Slag-blocks 311 

Slate,  specific  gravity  of  (Table  XXIV) 98 

weight  of  (Table  XXIV) 98 

19.  Slipperiness  of  asphalt 9 

21.  and  wood,  cure  for 10 

19.  granite 9 

19.  wood 9 

651.  Slips 428 

91 6a.  Slipperiness,  use  of  sand  to  prevent 640 

645.  Slope,  angles  and  length  of  (Table  LXVI) 425 

788.  of  footpaths 542 

954.  -walls,  specifications  for 6(53 

650.  Slopes,  covering  of , 428 

651.  drainage  of 4uO 

natural,  of  earth  (Table  LXV) 425 

654.                  of  embankments 432 

946.  Sloping  ground,  specifications  for  preparation  of fifil 

487.  Slow-setting  cement , 337 

13.  Smoothness,  economy  of 6 

906.  Snow,  disposal  of 639 

-ploughs,  form  of 783 

900.  removal  of 637 

903.  cost  of 638 

907.  from  footpaths > 539 

902.  in  Milan 637 

908.  weight  of  (Table  XXIV) 97,  640 

Soapstone,  specific  gravity  of  (Table  XXIV) 98 

weight  of  (Table  XXIV) 98 

Soft  interior  brick,  resistance  to  crushing  of  (Table  XXIV) 97 

specific  gravity  of  (Table  XXIV) 97 

weight  of  (Table  XXIV) 97 

453.  Soils,  natural  character  of 319 

100.  Source  of  Trinidad  asphaltum 52 

470.  Specific  gravity  of  American  natural  cements 328 


880  INDEX. 


ARTICLE  PAGE 

89c.  Specific  gravity  of  asplialtum 39,  97 

basalt  (Table  XXIV) 97 

Milestone  (Table  XI) 35 

brick  masonry  (Table  XXIV) 97 

cast  iron  (Table  XXIV)  97 

chalk  (Table  XXIV) 97 

clay  (Table  XXIV) 97 

with  gravel  (Table  XXIV). . .  97 

•  common  hard  brick  (Table  XXIV) 97 

460.  concrete  (  Table  XXIV) 97,  322 

crude  asphaltuni 55 

earth  (Table  XXIV) 97 

English  Portland  cement  (Table  XXIV) 97 

feldspar  (Table  XXIV) 97 

flint  (Table  XXIV) 97 

glass  (Table  XXIV) 97 

gneiss  (Table  XXIV) 97 

69.  granite  (Table  VI) , 29 

gravel  with  clay  (Table  XXIV) 97 

greenstone  (Table  XXIV) 97 

gunpowder  (Table  XXIV) 97 

ice  (Table  XXIV) 97 

lead  (Table  XXIV) 97 

lime  (Table  XXIV) 97 

limestone  (Table  XXII) 37 

liquid  bitumen  (Table  XXIV) 97 

mica  (Table  XXIV) 97 

mortar  (Table  XXIV) 97 

mud  (Table  XXIV) 97 

naphtha  (Table  XXIV) 97 

119.  paving-brick  (Table  XXIV) 86,  97 

petroleum  (Table  XXIV) 97 

pitch  (Table  XXIV) 98 

porphyry  (Table  XXIV) 98 

476.  Portland"  cement  (Table  XXIV) 97,  332 

pressed  brick  (Table  XXIV) 97 

quartz  (Table  XXIV) 98 

89.  refined  asphaltuni 40 

refined  Trinidad  asphaltum 58 

Koman  cement  (Table  XXIV) 97 

sand  (Table  XXIV) 98 

81.  sandstones  (Table  IX) 34 

serpentine  (Table  XXIV) 98 

shales  (Table  XXIV) 98 

shingle  (Table  XXIV)  98 


INDEX. 


881 


81.  Specific  gravity  of  slate  (Table  XXIV) 98 

soapstone  (Table  XXIV) 98 

soft  inferior  brick  (Table  XXIV) 97 

steel  (Table  XXIV) 98 

Stourbridge  fire-brick  (Table  XXIV) 97 

trap-rocks  (Table  XIV) 38 

Trinidad  asphalturn 40,  58 

water  (Table  XXIV) 98 

wood  (Table  XXII) 92 

wrought-iron  (Table  XXIV) 97 

943.  Specifications,  definition  of 660 

995.  deviation  from 673 

509.  (English)  for  Portland  cement 357 

1017.  forabulkbead 681 

960,  961.  arch-culverts 665,  666 

822.  artificial  curb  and  gutter 568 

979.  foundations 671 

796.  stone  footpaths 548 

pavements 314 

296.  asphalt-block  pavements 210 

780,  781.  footpaths 530,  532 

263.  pavement  on  bituminous  base . .  191 

264.  hydraulic  concrete  base. . . .  192" 

138.  Belgian- block  pavements 101 

303.  bituminous-rock  pavements 212 

818.  bluestone  curb 566 

954.  breast-walls 663 

828.  brick  gutters 572 

331-334.  pavements 233,  240 

784.  footpaths 541 

968.  masonry 667 

$30-831.  bridge-stones 573,  575 

715.  bridges 480 

423.  broken-stone  pavements 297 

984.  cast  iron 672 

291.  coal-tar  and  asphalt  pavements 205 

1018.  catch-basins 685 

951.  water-ditches 663 

972.  cement 669 

962.  centring 566 

944.  clearing 660 

1011.  cleaning  up 670 

945.  close  cutting 060 

1 35.  cobblestone  pavements 99 

982.  cofferdams 671 


882  INDEX. 


ARTICLE  "AGE 

782.  Specifications  for  compressed-asphalt-tile  footway-pavement 539 

795.  concrete  footpaths 547 

512-516,  977.  concretes. 359-36'>,  670 

303d.  condition  of  asphalt  pavements  at  end  of  guaran- 
tee period 217 

830.  crossing-stones o7d 

960.  culverts 665 

1018.  curbing 682 

950.  drains 663 

823.  dressing  old  curb 570 

970.  dry  box-culverts 668 

969.  walls 667 

948.  embankments 661 

1018.  flagging 682 

776.  flagstones 529 

741.  fencing 496 

978.  foundation  excavation 671 

947.  grading 660 

173.  granite-block  pavements 120 

816.  curb 565 

967.  grouting 667 

946.  grubbing 660 

829.  gutter-stones 573 

828.  gutters    572 

450^.  hydraulic-cement  pavement 314 

827.  laying  cobblestone  gutters 571 

965.  masonry  in  freezing  weather 666 

]018.  macadamizing 682 

956.  masonry 664 

1010.  miscellaneous  work 678 

976.  mortars 670 

952.  off -take  ditches 663 

964.  parapets 666 

97^  petroleum  residuum 40 

981.  piles 671 

971 .  pipe-culverts 668 

966.  pointing  607 

516.  preparation  of  roadbed  362 

948.  sloping  ground C,61 

927.  protection  of  trees 651 

993.  quality  of  materials 673 

832.  relaying  crossing-stones 575 

303c.  repair  of  asphalt  pavements 215 

1026.  repaving  ...    687 

824.  resetting  curb 570 


INDEX.  883 


ARTICLE  PAGE 

954.  Specifications  for  retaining- walls 663 

953.  rip-rap 663 

974.  sand 669- 

820.  setting  curb 567 

954.  slope  walls 663 

1031&.  for  sprinkling 706 

262.  Standard  Trinidad  asphalt  pavements 186 

1027.  street  cleaning 688 

797.  tar-concrete  footpaths 551 

1031«,  team  labor 705 

339,  422.  Telford's  pavement 247,  293 

980.  timber 671 

1016.  the  construction  of  a  highway 680 

1019.  the  supply  of  broken  stone 685 

338.  Tresaguet's  pavement 246 

975.  water 670 

963.  wing- walls 666 

213,  216.  wood  block  pavements 144,  151 

983.  wrougL  t-iron 67 1 

985.  interpretation  of 672 

986.  omissions  in 672 

473.  requirements  for  American  natural  cements . .  328 

996.  right  to  alter  details  in 678 

334.  variations  in,  for  brick  pavements 240 

895.  Speed  of  machine-brooms 635 

404.  steam-rollers 277 

401.  Spikes  in  steam-rollers,  defects  of 276 

1033.  number  of,  per  mile  of  track 720 

1033.  size  of ,  720 

992.  Spirituous  liquors 673 

1033.  Splice-joints,  number  of,  per  mile 720 

633.  Spoil-banks 422 

636.  form  of 422 

383.  Spreading  the  broken  stone 270 

1036.  Springfield  steam-roller 755 

554.  Springs  on  vehicles,  effect  of 388 

728.  behind  or  below  retaining- walls. 491 

859.  Sprinkling,  amount  of  water  required 590 

859.  broken-stone  pavements,  amount  of  water  required  for.  590 

1031&.  specifications  for 70(5 

911.  Sprinkling  of  streets 642 

1036-1040.  carts,  capacity  of  735,  773 

10^6-1040.  prices  of 735,  773 

897.  Squilgees  for  asphalt 636 

prices  of 770 


INDEX. 


ARTICLE  PAGZ 

888.  St.  Louis,  street-cleaning  in 633 

889.  St.  Paul,  street-cleaning  in 633 

644-646.  Stability  of  earth 425 

451.  pavements 319 

637.  Staking  out  borrow-pits. 423 

0^3.  bridges 655 

931.  culverts 650 

929.  curves 652 

934.  drains 655 

930.  side-slopes 652 

936.  street  contours 65t> 

938.  structures Go/ 

935.  vertical  curves .   65-") 

92S  work 652 

707.  Statistics  of  streets  for  each  of  fifty  of  the  largest  cities  in  the  United 

States  (Table  LXXXIII) 526 

Steam-drills,  price  of 7H2 

402.  -rollers,  and  grades 276 

404.  area  rolled  per  day 277 

403.  cost  of  maintaining. 276 

dimensions  of 755 

405.  manner  of  applying 278 

415.  picks  on,  objectionable , 289 

404.  speed  of 277 

Steel,  resistance  to  crushing  of  (Table  XXIV) , . .     97 

specific  gravity  of  (Table  XXIV) 97 

450/1.  trackways , 316 

weight  of  (Table  XXIV) 97 

897.  wire  brooms 636 

402.  Steepest  grade  upon  which  a  steam-roller  can  be  operated.   276 

541.  Steep  grades,  objections  to 382 

166.  pavements  on Ill 

64.  Stone,  absorptive  power  of 26 

412.  amount  of,  worn  away  annually  from  broken-stone  pavements  289 

877.  -block  pavement,  cost  of  cleaning 626 

load  drawn  by  a  horse  on  (Table  LVII) 380 

1038.  tools  used  in  the  construction  of 761 

transverse  rise  for  (Table  LXIV) 418 

601.  pavements,  maximum  grade  for 407 

159.  blocks,  joint-filling  for 109 

382.  broken,  quantity  required  per  mile  of  different  widths 270 

355.  coefficients  of   quality   for   broken-stone   pavements   (Table 

XXXVIII)  259 

1036.  crushers,  capacity  of 737 

10b6.  cost  of .737 


INDEX.  h85 

ARTICLE  PAG3 

357.  Stone  crushers,  cost  of  operating 26ft 

1036.  horse-power  required  for 737 

1036.  price  of 737 

1036.  size  of 73* 

368.  wear  of 26(5 

1036.  weight  of 737 

371.  crushing,  cost  of  (Table  XXX) 267 

1U36.  forks,  price  of 734 

151.  gutters I0f> 

1036.  hammers,  price  of ^54 

133.  pavements j;i) 

152  paving-blocks  at  street- junctions 10.V 

153.  culling  of 1U7 

149.  dressing  of 105 

351.  quality  of,  for  broken-stone  pavements 232- 

459.  concrete 321 

371.  quarrying,  cost  of  (Table  XXXIX) 268" 

1036.  rakes,  price  of 1  b4 

359.  shape  of,  for  broken-stone  pavements 265 

357.  size  of,  for  broken-stone  pavements 1C5 

438.  for  trackways 3C(» 

437.  trackways 30B 

365.  Stones,  breaking  by  hand •  fiG 

862.   Storage  and  delivery  of  broken  stone ,riH$> 

Stourbridge  fire-brick,  specific  gravity  of  (Table  XXIV) 9/ 

resistance  to  (Table  XXIV) 97 

crushing  of  (Table  XXIV) 97 

weight  of  (Table  XXIV).    97 

1036.  Straight-edge,  use  of 734 

225.  Street-car  rails  and  asphalt 163 

31.  tracks,  city  ownership  of IS 

868.  -cleansing 619' 

898.  carts  and  wagons 636 

893.  cost  of 635 

897.  hand-brooms  for 636- 

881.  in  Baltimore., 630 

878.  Berlin ('>?<* 

882.  Boston 030 

883.  Brooklyn  632 

884.  Cleveland GH2 

885.  Detroit t>3& 

y80.  London 630 

886.  New  York 633 

ST9.  Paris 629- 

887.  Philadelphia 632 


886  IXDEX. 


ARTICLE 

888.  Street-cleansing  in  St.  Louis 633 

889.  St.  Paul 633 

890.  Washington,  D.  C 633 

1027.  specifications  for 688 

876.  systems  of , 624 

899.  dirt,  disposal  of 630 

872.  dust,  composition  of 621 

749.  grades 506 

grades  in  various  cities  (Table  LXXXII). 508 

751.  intersections,  arrangement  of, 507 

7ti6.  carriageway  at , 525 

766.  increasing  width  of 525 

925.  trees  at 650 

152.  juncitons,  paving  with  stone  blocks 105 

763.  lines  and  monuments 520 

maintenance,  annual  cost  per  head  of  population  in  several 

cities  of  the  United  States  (Table  LXXXVII) 627 

875.  methods  of  cleansing 624 

872.  mud,  composition  of  (Table  LXXXV) 622 

]  042a.  name  plates 789 

891.  orderly  system 634 

878.  patrol  in  Berlin 628 

765.  profiles 523 

91 1 .  sprinkling G43 

911.  cost  of 643 

914.  frequency  of . 643 

913.  quantity  of  water  required 643 

916.  sea- water  for 645 

912.  systems  of 643 

767.  Street  statistics  for  each  of  fifty  of  the  largest  cities  in  the  United 

States  (Table LXXXIII) 526 

745.  Streets,  city 500 

57.                 excavations  in 23 

758.  subfoundation,  drainage  of 51 3 

759.  surface-drainage  of 51 4 

893.                  sweeping,  cost  of 635 

756.                 transverse  contour  of 512 

752.                                   grade  of 509 

$17.                  trees  on 647 

1J10.                  washing 642 

747.                  width  of 500 

in  various  cities  (Table  LXXXII) 50S 

468    Strength,  compressive,  of  concrete.   3i'5 

473.  of  cements 328 

400-468.  concrete .  822-325 


INDEX.  88' 


ARTICLE  PAGE 

491,499.  Strength  of  mortar 389,  344 

1045.  Structures,  annual  cost  of ! . .  797 

938.  setting  stakes  for 657 

1012.  Subletting  contract 679 

720.  Substructure  of  bridges 483 

723.  Surcharged  walls 486 

7:*1.  formula  for 491 

693.  Surface-drainage 459 

7o9.  of  streets 513 

1033.  -grader,  price  of 722 

1033.  useof 722 

850.  profit  of  improving  the 583 

377.  to  find  area  of  that  which  can  be  covered  by  a  cubic  yard 

of  broken  stone 269 

1008.  Suspend  work,  power  to 678 

1040.  Sweepers,  mechanical 771-777 

858,  Sweeping,  time  for.. 588 

893,  streets,  cost  of 625 

66,  Syenite 28 

876.  Systems  of  street  cleaning. .624 

856.  maintenance 586 

911.  sprinkling 643 


T 

797.  Tar-concrete  for  footpaths 551 

797.  footpaths,  specifications  for 551 

106.  -gas 74 

450e.  -macadam 313 

88a.  -mineral 39 

862.  Team-labor  and  materials 598 

103 1  a.  specifications  for 705 

422.  Tel  ford  pavements,  specifications  for 293 

842.  Telford's  method  of  broken-stone  pavements 249 

344.  defects  of 249 

483.  Temperature, effect  of  variations  on  cement 334 

257.  for  working  asphalt  paving  cement 184 

261 .  variation  in ,  and  asphalt  pavements 185 

103«.  Tensile  strength  of  asplialtum 62 

503.  mortar  (Table  XLVII) 347 

476.  Portland  cement 331 

268  Test  for  bituminous  rock 197 

126.  of  the  cleanness  of  sand 94 

476.  Testing  cement,  necessity  of , 331 

492.  machine  for  cement ,...». 340 


883  INDEX. 


ARTICLE  PAGE. 

60.  Tests,  breaking 24 

973.  cement,  specifications  for 669- 

60.  Tests,  crushing 24 

118.  of  brick 85-86- 

477.  cement 382 

942.  materials 6o9' 

61.  Rattler 25 

413.  Thickness,  loss  of,  on  broken-stone  pavements 289 

415.  manner  of  restoring,  on  broken-stone  pavements 289 

722.  minimum,  of  retaining- walls  ....    486 

714.  of  abutments 470 

for  arches  (Table  LXXVI) 478 

713.  arch 474 

arch  (Table  LXXV)    476 

758.  concrete 321 

154,  foundation 108 

429.  gravellayer 300 

378.  the  broken-stone  pavement 269 

384.  layers  of  broken  stone 271 

958.  Third-class  masonry 665 

689.  Tile-drains 457 

688.  Tiles,  diameter  of 457 

689.  form  of  457 

689.  length  of 457 

Timber  bridges,  dimensions  for  (Tables  LXXIX  and  LXXX) 484 

980.  specifications  for 671 

858.  Time  for  sweeping 587 

1002.  of  completion 67ft 

545.  Tires,  width  of 384 

527.  To  find  the  force  required  to  sustain  a  vehicle  upon  an  inclined  road.  377 

528.  pressure  of  a  vehicle  against  the  surface  of  an  inclined 

road 377 

131.  Tomkius  Cove  gravel 95 

131.  analyses  of     95 

1039.  Tools  employed  for  asphalt  pavements 762 

1038.  block  pavements 761 

73.                               in  the  manufacture  of  granite  paving-blocks 31 

1040.  for  cleaning,  price  of 770 

1037.                    maintenance  of  broken-stone  roads 598,  761 

1033.                    grading .- 711 

1032.                    grubbing,  prices  of 710 

1036.                    macadamizing 734 

1035.                     rock  excavation 728 

furnished  by  the  administration 598 

569.  Topography 391 


INDEX.  689 


ARTICLE  PAGE 

439.  Trackways,  cost  of 306 

438.                       inltaly 306 

384.                       size  of  stone  for 306 

450rt.                     steel 316 

437.                        stone 303 

597.  Tractive  force  required  in  descending  inclines 406 

force  required  to  move  a  load  of  one  ton  on  different 

pavements  in  Europe  (Table  LI) 87") 

force  required  to  move  a  load  of  one  ton  on  different  road-  ' 

surfaces  (Table  L) 3.2 

531.  Tractive  power  and  gradients   377 

532,533.                      ofhorses 377 

at  different  velocities  (Table  LIII) 378 

517,  520.  Traction,  resistance  to  (Table  L) 366,  372 

43.  Traffic  census 17 

393.                defects  of  compacting  the  broken  stone  by  the 273 

228.               sustained  by  asphalt 167 

629.  Transverse  balancing 421 

757.                      contour  of  streets 513 

936.                                                  stakingout 656 

618.                                        roadways 418 

625.                                    on  hillside  roads 420 

756.                      grade  of  streets 5i2 

467.                      strength  of  concrete , 32"> 

670.  Transport  of  earth 444 

o.  Transportation-wagon,  cost  of 2 

86.  Trap- rocks    38 

86.  colorof 38 

87.  resistance  to  crushing  of  (Table  XIV) 38 

87.                      specific  gravity  of  (Table  XIV) 38 

87.                      weight  of  (Table  XIV) 38 

925.  Trees  at  street-intersections 650 

924.             distance  apart  to  plant 650 

920.             financial  value  of 649 

919.             on  Belgian  road 648 

836.  clay  roads 578 

917.                  roads 647 

837.  sand  roads 579 

917.  streets 647 

918.  the  French  roads 648 

927.             protect  ion  of 651 

922.             qualities  of. 649 

922.             selection  of 649 

927.             specifications  for  protection  of 651 

917.             useof 647 


890  INDEX. 


ARTICLE  PAGE 

338.  Tresaguet's  system  of  broken-stone  pavements 246 

100.  Trinidad  asphaltum 53 

100(2.  analyses  of  (Tables  XIV  a  and  XVI  a) 43-55 

lOte.  preparation  of 55 

104.  price  of,  in  1893 73 

100.  source  of 53 

740.  Tunnels 495 

Types  of  timber  bridges 484 

U 

607.  Undulating  grades 413 

91«.  Uiutahite 41 

847.  Unnecessary  grades,  profit  of  eliminating 581 

704.  Use  of  catch-pools 466 

124.               sand 93 

105.  Uses  of  asphaltum  74 

72.                granite 31 

<J,  83.          limestone 4,  36 

464.  Usual  proportions  for  concrete 323 

V 

Value  of  bluestone  used  for  street  purposes  in  1889  (Table  XI) 35 

70.  granite  used  for  street  purposes  in  1889  (Table  VII) 30 

842.  improvements '. 580 

limestone  used  for  street  purposes  in  1889  (Table  XIII)  . .     37 

sandstone  used  for  street  purposes  in  1889  (Table  X) 35 

334.  Variations  in  specifications  for  brick  pavements 240 

of  temperature,  effect  of,  on  asphalt  pavements .  159 

482.  cement  334 

483.  mortar 334 

89.  of  asphaltum 39 

120.  Varieties  of  wood  used  for  paving 87 

543.  Vehicles,  character  of    .* 305 

400.                    loaded  pressure  of • 275 

638.  Vegetable  soil,  shrinkage  of 423 

610.  Vertical  curves 415 

935.                            staking  out 655 

Vitrified  pipe,  weight  of  (Table  LXXI) 471 

cost  of  (Table  LXXI) ...  471 

461 .  Voids,  determination  of 322 

372,  461.       in  broken  stone 267,  322 

373.  to  determine 268 

372,  461.  gravel 267,  322 

127,462.  sand 94,322 


INDEX.  891 


ARTICI.K  PAGE 

2«0.   Vulcanite  pavement 202 

881.  Wages,  in  Baltimore 630 

882.  Boston 630 

1043.  Europe 793 

879.  Paris 62'J 

73.  of  paving-block  makers 32 

W 

5.  Wagon-transportation,  cost  of 2,  794 

670.  Wagons,  dump 444 

910.  Washing,  street 6-12 

890.  Washington,  D.  C.,  cleaning  streets  in 633 

56.  Waste  of  money  in  opening  pavements 23 

103^.  Water,  action  of,  on  bitumen 62 

484.  amount  of,  absorbed  by  cements  (Table  XLIV) 385 

484.  required  for  mortars 305 

859.  sprinkling,  broken-stone  pavements 589 

695.  breaks,  objections  to 461 

497.  for  mortar,  quality  of 343 

224.  injurious  to  asphalt 160 

582.  on  mountain  roads 401 

484.  quantity  of,  for  mortar 335 

463.  required  for  concrete 323 

913.  street-sprinkling 643 

specific  gravity  of  (Table  XXIV) 97 

975.  specifications  for 670 

weight  of  (Table  XXIV) 97 

392.  Watering  broken-stone  pavements ...  273 

392.  effect  of  excessive 273 

794.  Wear  of  artificial  stones 546 

63.  asphalt  blocks 26 

231.  pavements 168 

63.  brick 26 

63,  409.          broken-stone  pavements , 26,  283 

63,  168-  granite  pavements 26.  143 

63,  202.  wood  pavements 26,  118 

368.  stone-crushers 266 

2">3.   Wearing  surface  of  Trinidad-asphalt  pavements 182 

729.  Weep  holes 491 

256.  Weight  of  a  cubic  yard  of  asphalt  paving-cement 184 

470.  American  natural  cement  (Table  XXIV) 97 

256.  asphal turn  (Table  XXIV) 97 

basalt  (Table  XXIV)  97 

bitumen  (Table  XXIV) 97 


892  INDEX. 


ARTICLE 

256.  Weight  of  bituminous  limestones  (Table  XXIV) 97 

bluestone  (Table  IX) 35 

brick  (Table  XXI) 87 

masoiiiy  (Table  XXIV) 97 

374.  broken  stone 2C8 

cast  iron  (Table  XXIV) 97 

48(X  cement 333 

English  Portland  (Table  XXIV) 97 

707.  cement  pipe  (Table  LXXII) 471 

Koseudale  (Table  XXIV) 97 

chalk  (Table  XXIV) 97 

clay  (Table  XXIV) 97 

with  gravel  (Table  XXIV) 97 

common  hard  brick  (Table  XXIV) 97 

457.  concrete  (Table  XXIV) 97,  321 

971.  culvert-pipe  (Tables  LXXI,  LXXVII) 471,  479,  668 

drain-tiles  (Table  LXXVII) 479 

earths  (Table  XXIV) 97 

feldspar  (Table  XXIV) 97 

flint  (Table  XXIV) 97 

French  Portland  cement  (Table  XXIV) 97 

glass  (Table  XXIV) 97 

gneiss  (Table  XXIV) 97 

69.  granite  (Table  VI) 29 

gravel  with  clay  (Table  XXIV) 97,  801 

gunpowder  (Table  XXIV) 97 

1038.  hand  rammers 761 

ice  (Table  XXIV)  97 

709.  iron  pipes  (Table  LXXIII) 472 

lead  (Table  XXIV) 97 

lime 97 

84.  limestone  (Table  XII) 97 

liquid  bitumen  (Table  XXIV)  97 

mason  ry  (Table  XXIV) 97 

mica  (Table  XX IV) 97 

mortar  (Table  XXIV) 97 

mud  (Table  XXIV) 97 

naphtha  (Table  XXIV) 97 

paving-bricks  (Tables  XXI,  XXIa,  XXIV) 87,  88,  97 

peat  (Table  XXIV) £8 

petroleum  (Table  XXIV) 98 

1033.  picks 711 

pitch  (Table  XXIV) 98 

433.  pit-gravel 301 

porphyry  (Table  XXIV) 98 


INDEX.  893 


ARTICLE  PAGE 

473.  Weight  of  Portland  cement  (Table  XXIV) 97,  328 

pressed  brick  (Table  XXIV) 97 

quartz  (Table  XXIV) 98 

rails    720 

791.  rammers  for  concrete 543 

road  rollers 752-756 

Roman  cement  (Table  XXIV) 97 

Rosendale  cement  (Table  XXIV) 97 

130.  sand  (Table  XXIV) 94,  98 

81.  sandstones  (Table  IX) 34 

scrapers 713 

serpentine  (Tnble  XXIV) 98 

shales  (Table  XXIV) 98 

shingle  (Table  XXIV) 98 

slate  (Table  XXIV) 98 

snow  (Table  XXIV) 98,  640 

soapstone  (Table  XXIV)  5 98 

soft  inferior  brick  (Table  XXIV) 97 

steel  (Table  XXIV) 98 

1036.  stone  crushers . , 740 

Stourbridge  fire-brick  (Table  XXIV) 97 

87.  trap-rocks  (Table  XIV) 38 

water  (Table  XXIV) 98 

wood  (Tables  XXII,  XXIV) 92,  97 

wrought-iron  (Table  XXIV) 97 

707.  vitrified  pipe  (Table  LXXI) 471 

550.  Wheels,  advantages  of 387 

410.  effect  on,  on  pavements. 284,  388 

518.  power  required  to  draw,  over  obstacles 366 

520.  rolling,  resistance  of 371 

549.  size  of 387 

1038.   Wheelbarrows 716 

327.  Wheeling,  plan  of  brick  pavements 232 

613.  Wheel  way,  minimum  width  of 416 

611.  Wide  roads ; 416 

747.  Width  of  carriageway,  increasing  of,  at  street-intersections 506 

747.  city  streets 506 

769.  footpaths 5?7 

191.  joints  in  wood  pavements 134 

616.  land  appropriated  in  various  localities  for  roads 416 

617.  mountain  roads 417 

147.  paving-blocks 104 

•611.  roads 416 

,587.  roadways  on  curves 403 

sidewalks  in  various  cities  (Table  LXXXII) 508 


894  INDEX. 


ARTICLE  PA&E 

587.  Width  of  streets  in  various  cities  (Table  LXXXII) 5C8 

545.  tires    384 

548.                    tires  in  Austria 385- 

547.                                Bavaria 385- 

112.                           ordinance  regulating 78 

546.  in  France 385 

411.  Wind,  effect  of,  on  roads 28l> 

963.   Wing  walls,  specifications  for 606 

743.  Wire  fence,  cost  of 49t> 

1038.  Wire  screens,  price  of 761 

120.  Wood... . ..     86 

122.  absorptive  power  of  (Table  XXIII) ..< 93 

450.  and  iron,  combination  of  311 

183.  blocks,  number  per  square  yard 1^9 

188.  chemical  treatment  of 131 

122.  creosoting,  advantage  of i/;i 

188.  cost  of 132 

748.  for  footpaths 506 

177.  pavements,  advantages  of  124 

874.  amount  of  dirt  produced  by 624 

181.  and  death  rate 12? 

201,  208,  2166.  cedar  blocks 137,  140,  154 

186.  chief  cause  of  the  failure  of 130 

877.  cost  of  cleaning 626 

205.  cost  of  construction  (Table  XXXIII) 139 

206.  maintenance 139 

2l6e.  cotton  wood  blocks 155 

27,  193.  durability  of 11,  135. 

184.  essentials  necessary  to  successful  construction  . .  130 

185.  foundations  used  for 1 30 

2160.  gum  blocks 1 55- 

216c.  Karri  wood 1 54 

27.  lifeof 11 

214.  maintenance  by  contract 147 

599.  maximum  grade  for 40T 

209.  mesquite  block 141 

216a.  microbes  in 15IJ 

179.  objections  to. 12"> 

216d.  pine  blocks 1 55 

216/.  redwood  block 155 

19.  slipperiness  of 9 

213,  216.  specifications  for 144,  151 

transverse  rise  for  (Table  LXIV) 418 

182.  variety  of  systems 1:29 

63,  202.  wear  of 26,  137 


INDEX.  895 


ARTICLE  PA-TE 

190.  Wood  paving  blocks,  expansion  of 134 

183.  shape  of 129 

181.  size  of 127 

189.  dimensions  of  blocks  for 133 

192.  filling  for  joints 135 

187.  quality  of  the  wood 131 

191.  width  of  joints 135 

188.  preservation  of. , , 131 

121.  quality  of,  for  paving 93 

resistance  to  crushing  of  (Table  XXII) 92 

specific  gravity  of  (Table  XXII) 92 

120.  varieties  used  for  paving 92 

weight  of  (Table  XXII) 92 

719.  Wooden  bridges 481 

dimensions  of  (Tables  LXXIX  and  LXXX) 484 

736.  railings  for  road  protection 493 

188.  Woods  best  adapted  to  chemical  treatment 131 

1001.  Work,  commencement  of 676 

998.  defective 674 

534.  done  by  horses 378 

1007.  faithful  performance  of,  bond  for 678 

999.  how  measured 674 

1010.  miscellaneous 678 

1008.  Work,  power  to  suspend 676 

1008.  progress  of 676 

1013.  Workmen,  payment  of 679 

983.  Wrought-irou,  specifications  for 671 

91a.  Wurtzilite..  41 


Z 

680.  Zero-point,  to  ascertain,  by  calculation 454 

591.  Zigzags,  objections  to 403 


INDEX   TO   ADVERTISEMENTS. 

PAGE 

American   Bridge  Company 5 

Austin  Manufacturing  Company,  The  F.  C 3 

Austin  &  Western  Company 2 

Bacon,  Earl  C 7 

Buffalo  Pitts  Company,  The 6 

Climax  Road  Machine  Company,  The 6 

Farrel  Foundry  and  Machine  Company 7 

Rand  Drill  Company I 

Rendrock  Powder  Company i 

Russell  &  Co t> 

Wilson  &  Baillie  Manufacturing  Company,  The 4 

Wiley  &  Sons,  John 8 


Y.r-  sq 


CONTRACTORS 

AVOID  ACCIDENTS  I 
PREVENT  LAWSUITS  I 
SAVE  MONEY 

IF  WORKING  IN  THE  CITY  LIMITS, 

BY   USIfiG 

RACKAROCK 

THE  ONLY  SAFE  HIGH  EXPLOSIVE. 


RACKAROCK  is  a  blasting-powder  of  exceptional  strength, 
and  is  formed  by  the  union  of  two  ingredients,  both  of  which  are 
absolutely  non-explosive  until  combined  by  the  user.  Rackarock 
does  not  freeze  in  the  coldest  weather,  equally  effective  in  wet  or 
dry  holes,  and  packs  closer  than  dynamite:  furnished  in  two  grades. 
By  reason  of  its  safety  it  is  especially  well  adapted  to  water- 
works  and  highway  construction  in  crowded  sections  of  the  city. 

Shipped  and  stored  like  ordinary  merchandise. 


Rendrock  Powder  Co., 


YORK. 


IMPROVED 

"LITTLE  GIANT  "and"  SLUGGER" 

ROCK-DRILLS 

For    Contractors    for    Sewers,    Cellars, 
Streets,   Mines,  Quarries,  etc. 


ALSO 


AIR-COMPRESSORS, 

PORTABLE  BOILERS,  HOSE,  WIRE  ROPE,  STEEL,  ETC. 


R  AN D  DRILL  CO. 

and  full  ^Lr. 

Information. 

J28  BROADWAY,       -       NEW  YORK. 


GOOD   ROADS 

Can  be  made  and  maintained  only  by  the  use  of 

GOOD  ROAD  MACHINERY. 

AUSTIN    &   WESTERN  CO.,  Ltd.,  Chicago,  I1L,  have  the 

LARGEST  and  BEST  line  of  Road  Machinery  in  the 

world.     It  includes  the  celebrated 


£ 


ROAD  MACHINES,  ROAD  ROLLERS.  DRAG  AND 
TONGUE  SCRAPERS,  ELEVATING  GRADERS,  STREET 
SWEEPERS,  ROAD  PLOWS,  ROCK  CRUSHERS,  WHEEL 
SCRAPERS,  DITCHING  MACHINES, 
AND  STREET  SPRINKLERS. 


SEND    FOR    CATALOGUE. 


AUSTIN  CRUSHERS 


TECHNICALLY  AND 
MECHANICALLY 
WITHOUT  A  FAULT 


LEAST  LIABLE  TO  GET 
OUT  OF  REPAIR,  AND 
MOST  ECONOMICAL  IN 
CONSUMPTION  OF  POWER 


WRITE  TO   DEPARTMENT  A 

for  special  catalogue  of  Crushers, 

Dump  Cars  and  Contractors' 

Machinery. 


Contractor  s  Austin  Reversible 

Dump  Wagon  Road  Roller 


Austin 
Street  Sweeper 


Austin 
Contractor's  Plow 


Austin  Wheeler 


Austin 
Drag  Scraper 


Austin  Reversible  Road  Machine         Austin  Rock  Crusher  and  Elevator 


R  C.  AUSTIN  MFG.  CO.,  Harvey,  111. 


T.  SBTBT  DUMABY,  President. 
C.  OLIN  JOHNSON,  Viee-President. 


E.  E.  BAILLIE,  Secretary. 
P.  B.  JOHNSON,  Treasurer. 


The  Wilson  &  Baillie  Manufacturing  Co, 

Main  Office  and  Factory,  85-93  Ninth  Street,  Brooklyn,  N.  Y. 

KAXUFAOTOBEXS  OF 

ARTIFICIAL  STONE. 

For  Sidewalks,  Driveways,  Copings,  Steps,  Rat/road  Depot  Platforms, 

Flooring  for  Warehouses  and  Apartment  Houses,  Water-tight 

Cellar  Floors,  and  Improved  Stable  Floors. 

KOSMOCRETE  STEEL-BOUND  CURB. 


The  Steel-Bound  Curb 
is  superior  to  any  nat- 
ural stone. 

L*id  in  ten=foot 
lengths,  with  invisible 
joints,  with  concrete 
foundations,  is  never 
out  of  line. 

Galvanized  steel  edges 
cannot  rust  or  break. 

It  is  the  most  beauti- 
ful and  durable  curb 
laid,  and  with  gutter 
combined  is  the  ideal 
for  asphalt,  brick,  or 
macadam  streets. 


HEAVY  CONCRETE   CONSTRUCTION  i 

Steel-Bound   Curb  has  been  laid  in  the  following  cities  : 

NEW   YORK,  PROVIDENCE,  NEW  HAVEN,  UT1CA, 

BROOKLYN,  NEWPORT,  ALBANY,  AND 

BOSTON,  HARTFORD,  TROY,  SCHENECTADY. 

By  permission  we  refer  to  the  Engineers  and  Architects  in  charge  of  the  following  work: 

Armories:   a^d  Regiment,  Brooklyn;    i4th 


Bowling  Green  Building,  Kosmocrete  walks 

laid  on   Broadway  and    Greenwich    Street 

fronts. 
Six  miles  of  foundations  for  Union  Elevated 

Railroad  of  Brooklyn. 

Swimming  Tank,  Bergen  Beach,  Broooklyn. 
Sea  Wall,  Wallabout  Market,  Brooklyn. 
Causeway,  New  York  Navy  Yard,  Brooklyn. 
Sidewalks.  Curbs,  etc..  Terminals,  New  York 

and  Brooklyn  Bridge. 
Sidewalks.    Curbs,    etc.,    New    York    State 


Regiment,  Brooklyn;    Cohoes,  Utica,  Hor- 

nellsville. 
Sidewalk,  five  miles  long,  eight  feet  in  width, 

Ocean  Parkway,  Brooklyn. 
Capitol,    Albany,  N.  Y. ;    Floor    of  Terrace, 

10,000  sq.  feet. 
Sidewalk  and  Curb,  Rensselaer  County  Court 

House.  Troy,  N.  Y. 
Fireproof   Floors.  Abraham  &  Straus's  New 

Warehouse,  Brooklyn. 


15, 

We  can  supply  promptly  any 
ordinary  order  for  Steel  Bridges, 
Buildings,  Roofs,  Trasses,  Columns, 
Girders,  Beams,  Channels,  Angles, 
Plates,  etc. 

Steel  Frame  Work  for  Mills, 
Factories,  Public  Markets,  Sheds, 
Shops,  Power-Hotises,  Piers,  etc. 


ompany 


Engineers  ,  Manttf  acttirer  s  , 
Contractors 


Metallic  Structures 
of  Every  Description 


Branch  Offices  and  Works : 

Albany,  N.  Y.       Duluth,  Minn.  Pittsburg,  Pa. 

Athens,  Pa.  East  Berlin,  Conn.  Rochester,  N.  Y. 

Boston,   Mass.      Elmira,  N.  Y.  Seattle,   Wash. 

Buffalo,  N.  Y.          Groton,  N.  Y.  San  Francisco.  Cal. 

Baltimore,  Md.    Horseheads,  N.  Y.  Salt  Lake  City.  Utah. 
Butte,  Mont.         Lafayette,  Ind.         Sydney,  N.  S.  W. 
Columbus,  Ohio.  Milwaukee,  Wis.       Trenton,  N.  J. 
Chicago,  111.          Minneapolis,  Minn.  Wilmington,  Del. 
Canton,  Ohio.       New  Orleans,  La.    Youngstown,  Ohio. 
Cleveland,  Ohio.  Pencoyd,  Pa.  London,  England. 

Denver,  Colo.       Philadelphia,  Pa. 


THE    O.    S.    KELLY    CO., 

SPRINGFIELD,    OHIO. 

Steam    Road    Rollers. 

Steam    Asphalt    Rollers. 

Steam  Rollers  for  Golf  Links. 

HANDSOME   CATALOGUES    SENT    ON    APPLICATION. 

CLIMAX  ROAD  MACHINE  CO., 

MARATHON,    N.     Y. 

Stone-Crushers  (capacity  70  to  400  tons  per  day), 

Complete  Stone-crushing  Plants, 
Road  Machines,  Automatic  Distributing  Wagons, 
Earth-handling  Machinery. 

GENERAL   AGENCIES: 

CLIMAX    ROAD    MACHINE    CO.,    HARRISBURG,    PA. 

CLIMAX    ROAD    MACHINE    CO.,    PITTSBURG,    PA. 

JULIAN  SCHOLL  &  CO.,  126  LIBERTY  ST.,   NEW  YORK, 


'Russell'    Steam 
Road   Rollers. 

BUILT    IN  ALL  SIZES. 

For  Contractors,  Corporations,  and 
Municipalities. 

RUSSELL  &  CO., 

MASSILLON,  OHIO. 
JULIAN   SCHOLL    &   CO., 

AGENTS, 

126  Liberty  Street,  New  York. 


BUFFALO    PITTS    STEAM    ROAD-ROLLERS. 

Double  Engines.  Sizes,  8, 10, 12,  and  15  Ton. 

Bought  by  the  United  States  Government. 

Massachusetts    Highway  Commission, 

New  York  City,  etc.,  etc. 

BUILT   BY 

BUFFALO  PITTS  COMPANY 

BUFFALO,   N.   Y., 

150  Nassau  St.,  New  York  City 
15  Court  Square,  Boston,  Mass. 


FARR EL ' S 

ROCK- 
CRUSHER 

S  TANDARD  OF  THE  WORL  D 

Complete    Rock-Crush- 
ing Plants  of  100  to 
loootons  per  day . 
our  specialty. 

SEND      FOR     COMPLETELY     ILLUSTRATED      CATALOGUE. 


FARREL'S    ROCK-CRUSHING  PLANT. 

FARREL    FOUNDRY 

AND    MACHINE    CO., 

EARLE  C.  BACON, 

ENGINEER, 

HAVEMEYER    BUILDING,    NEW    YORK,       BACON'S  PATENT  SWING-SCREEN. 


FOR    MUNICIPAL  ENGINEERS. 

Inspection  of  the  Materials  and  Workmanship  Employed  in  Construction.    By 

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xvi -f- 540  pages.      i2mo.      Cloth,  $3.00. 

Order  through  your  bookseller,  or  copies  will  be  forwarded,  postpaid,  by  the  publishers  on 
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SHORT-TITLE    CATALOGUE 

OF  THE 

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Morgan's  The  Theory  of  Solutions  and  its  Results 12mo,  1  00 

Elements  of  Physical  Chemistry 12mo,  2  00 

Nichols's  Water-supply  (Chemical  and  Sanitary) 8vo,  2  50 

O'Briue's  Laboratory  Guide  to  Chemical  Analysis 8vo,  2  00 

Pinner's  Organic  Chemistry.     (Austen.) 12mo,  1  50 

Poole's  Calorific  Power  of  Fuels 8vo,  3  00 

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and  Woodman's  Air,  Water,  and  Food 8vo,  2  00 

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metallic)  Oblong  8vo,  morocco,  75 

Rideal's  Sewage  and  the  Bacterial  Purification  of  Sewage... 8vo,  3  50 

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Stockbridge's  Rocks  and  Soils 8vo,  2  50 

*  Tillman's  Descriptive  General  Chemistry 8vo,  3  00 

5 


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Weislmch's  Hydraulics.     (Du  Bois.) 8vo,  5  00 

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LAW. 

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MANUFACTURES. 

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Supplement 12mo,  250 

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Spencer's  Sugar  Manufacturer's  Handbook  . . .  .16mo,  morocco,  2  00 
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10 


MATERIALS  OF  ENGINEERING. 

(See  also  ENGINEERING,  p.  7.) 

Baker's  Masonry  'Construction 8vo,  $5  00 

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Church's  Mechanics  of  Engineering — Solids  and  Fluids 8vo,  6  00 

Du  Bois's  Stresses  in  Framed  Structures Small  4to,  10  00 

Johnson's  Materials  of  Construction 8vo,  6  00 

Lanza's  Applied  Mechanics 8vo,  7  50 

Martens's  Testing  Materials.     (Heuning.) 2  vois.,  8vo,  7  50 

Merrill's  Stones  for  Building  and  Decoration 8vo,  5  00 

Merriman's  Mechanics  of  Materials 8vo,  4  00 

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Pattou's  Treatise  on  Foundations 8vo,  5  00 

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Thurston's  Materials  of  Construction , 8vo,  5  00 

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11 


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MECHANICS-MACHINERY. 

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12 


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13 


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